Phase Locked Loop with vacuum tubes.
Patrick Turner
locked loop using vaccum tubes, and hundreds of images came up but NOT
ONE with a phase locked loop that could be used for better AM
detection.
I must away to my shed to do some work rather than chase fancy fairy
circuits on the Internet.
Patrick Turner.
Arny Krueger
"Patrick Turner" <in...@turneraudio.com.au> wrote in message
news:d791dbd6-cefd-490c...@j9g2000prj.googlegroups.com...
If they'd ever declassify some of the radar sets I worked on in the late
1960s... 400+ tubes each, and a number of PLL-stabilized thises and thats.
Patrick Turner
> On Tue, 19 Jul 2011 11:40:47 -0400, "Arny Krueger" <ar...@cocmast.net>
> wrote:
>
>
>
> >"Patrick Turner" <i...@turneraudio.com.au> wrote in message
I'm not planning to build AM radios for ppl with 400+ tubes. 4 tubes
is about enough, 1 x RF amp, 1 x F converter, 1 x IF amp, and 1 x twin
triode for the CF detector. Then 3 tubes for a nice 9W SE amp for the
speaker, which will be a modern type, not the old field coil type made
in 1935 and crumbling to bits.
I like to use 1 paralleled twin triode for tone control, same for SE
amp input tube, and an EL34 for output tube in 50% SEUL mode. 9W is
doable with B+ at OPT = +390V and 70mA for audio amp and another 15mA
for everything else. Some old sets using Si diodes can provide this
power easily, but if not then usually its possible to use an EL34 in
triode with the existing OPT if its good enough, and get 4.5Watts of
SET power which is much better than 6F6, 6BQ5, 6V6, 6M5, 6AR5, 6BW6,
etc. The EL34 is placed where the 5Y3, 80, or other rectifier was. A
mains fuse and HT fuse is added, so the fuckin' old set don't burn
down anyone's house.
The nice roomy chassis made in the years just before and after WW2 are
very easily rewired with stuff that works better.
I'm having to build a dual concentric speaker for a set I'm doing now
- 10" driver with 2" tweeter slung in the middle so it fits the
cabinet made in 1940 without any changes, and all that's needed are
slightly heavier guage wood screws.
But If I wanted to make a PLL for AM detection, I guess theory tells
me I'd have to have circuit to detect the phase difference of the IF
signal with a 455kHz crystal oscillator, so something like an FM
discriminator which produces a good swinging DC voltage, which will
swing enough adjust the variable oscilator in the F converter section
of the AM radio, and then hold the oscillator F so darn accurate the
IF and crystal oscillator are dead accurately aligned, without being
even one wave out. Trouble is trying to vary oscillator F in tube gear
and at such LF as 455kHz takes large variations of C in tank circuits,
and all I could find to do this was a bunch of paralleld 68V zener
diodes where their C varies like a varicap before you reach the zener
voltage. Varicaps diodes require very low circuit signal voltages. But
higher voltage rated zeners allow the kind of voltages seen in tube
gear - always much higher than in SS junk.
But it seems no bastard has ever bothered to spend a month or three to
get a PLL working for AM reception with tubes.
Its like Multiplex Stereo decoding, no bastard has ever produced a
fully tubed version of a Gilbert Cell to get stereo signals from an FM
composite signal - they all fall back onto a diode matrix circuit.
So they say they like to use tubes, but they fuckin' won't, and don't
have all the answers.
At least 5 bjts are needed for a Gilbert Cell, so 5 triodes are needed
for a tubes version, and who wants to use more tubes just for
detection than the number used for the rest of the set?
So the CF detector of mine is lookin' good, so simple and effective.
I've even used my detector within my home brew variable RF oscillator
so that the modulated RF output is detected, and fed into a diff amp
with incoming audio F and the signal sent to modulate the RF has an
error signal to linearize the envelope. This reduced the envelope
shape THD from about 5% at 95% mod to about 1%, - a very welcome
improvement so that detector distortions in receivers being tested
would not be confused with distortion in the incoming test signal.
Patrick Turner.
>
> Every vacuum tube 'electronic' (meaning CRT vs mechanical) television
> receiver had at least one: the horizontal oscillator/sync.
>
> In color sets you also have the chroma osc.
Patrick Turner
> >I'm not planning to build AM radios for ppl with 400+ tubes
>
Of course. I was yus Yoking.
>
> >. 4 tubes
> >is about enough, 1 x RF amp, 1 x F converter, 1 x IF amp, and 1 x twin
> >triode for the CF detector.
>
> Bean counter.
But all those manufacturers before me used far fewer tubes.....
>
>
>
>
>
> > Then 3 tubes for a nice 9W SE amp for the
> >speaker, which will be a modern type, not the old field coil type made
> >in 1935 and crumbling to bits.
> >I like to use 1 paralleled twin triode for tone control, same for SE
> >amp input tube, and an EL34 for output tube in 50% SEUL mode. 9W is
> >doable with B+ at OPT = +390V and 70mA for audio amp and another 15mA
> >for everything else. Some old sets using Si diodes can provide this
> >power easily, but if not then usually its possible to use an EL34 in
> >triode with the existing OPT if its good enough, and get 4.5Watts of
> >SET power which is much better than 6F6, 6BQ5, 6V6, 6M5, 6AR5, 6BW6,
> >etc. The EL34 is placed where the 5Y3, 80, or other rectifier was. A
> >mains fuse and HT fuse is added, so the fuckin' old set don't burn
> >down anyone's house.
> >The nice roomy chassis made in the years just before and after WW2 are
> >very easily rewired with stuff that works better.
> >I'm having to build a dual concentric speaker for a set I'm doing now
> >- 10" driver with 2" tweeter slung in the middle so it fits the
> >cabinet made in 1940 without any changes, and all that's needed are
> >slightly heavier guage wood screws.
>
> Yeah. I cut costs by using old chassis/enclosures to stick something
> else in too.
I'm doing this for part of my living. The labour time I spend on a
radio rebuild can be hundreds of hours. I enjoy it, but the pay is
maybe $2 an hour.
I often must wind a new OPT about 4 times bigger than the Walnut
Acountant model of OPTs which were included in the scam behind the
brand name.
>
> >But If I wanted to make a PLL for AM detection, I guess theory tells
> >me I'd have to have circuit to detect the phase difference of the IF
> >signal with a 455kHz crystal oscillator,
>
> Only if you kept IF conversion.
Even if I didn't, one still has to have an oscillator track the RF,
and be accurate. DG Tucker's Synchrodyne of 1947 is a difficult thing
for anyone to build at home, but at least its tubed, and perhaps could
be improved a lot if a couple of modern methods were applied.
But I also like the idea of a 2Mhz IF so that the side band cutting is
minimised but it probably requires 6 tuned ciricuits in 3 IFTs to get
sufficient skirt selectivity.
Just means two IF amps. Same CF detector could be used, but 6DJ8 would
be a better tube for the higher F.
> > so something like an FM
> >discriminator which produces a good swinging DC voltage, which will
> >swing enough adjust the variable oscilator in the F converter section
> >of the AM radio, and then hold the oscillator F so darn accurate the
> >IF and crystal oscillator are dead accurately aligned, without being
> >even one wave out.
>
> It's called a PLL in modern parlance.
>
> It isn't quite the 'miracle' you imply with "so darn accurate,"
> although it is.
In a tube FM set there is often 4 triodes for the RF amp, mixer,
oscilator and rmaining triode is for AFC, where the dc from
discriminator is applied to the grid of 1/2 a 6AQ8 or 12AT7 to change
gm of the triode which changes the C looking into the anode. The
slight change of C is enough to swinf F a long way at 100MHz, but not
at 455kHz. Its not the same4 as PLL though.
>
> You're thinking like proportional error, which would have to be
> incredibly small requiring huge gain, but a PLL isn't proportional
> "automatic frequency control." A PLL, or "automatic phase control,"
> integrates the difference by comparing phase and because it behaves as
> a frequency error integrator the frequency error 'naturally' goes to
> 0.
Well if you know so much about PLL, I guess we can look forawrd to you
providing us with a schematic next week.
>
> > Trouble is trying to vary oscillator F in tube gear
> >and at such LF as 455kHz takes large variations of C in tank circuits,
> >and all I could find to do this was a bunch of paralleld 68V zener
> >diodes where their C varies like a varicap before you reach the zener
> >voltage. Varicaps diodes require very low circuit signal voltages. But
> >higher voltage rated zeners allow the kind of voltages seen in tube
> >gear - always much higher than in SS junk.
>
> Reactance tube.
Does not do enough at 455kHz.
>
> >But it seems no bastard has ever bothered to spend a month or three to
> >get a PLL working for AM reception with tubes.
>
> Of course they did. Try looking up synchrodyne.
>
> http://www.thevalvepage.com/radtech/synchro/section5/section5.htm
The schematic there has NO PLL and **IS D.G. Tucker's 1947
Synchrodyne** circuit.
The main difficulty with the synchrodyne is how to make the ring
modulator transformer, amoung other problems.
By the time someone has fucked around with Tucker's circuit one would
have better spent the time on a superhet.
>
> The terminology "Phase lock loop" didn't come about till the 1960s
> when integrated circuit 'building blocks' prompted the creation of
> more generic 'building block' names.
Indeed.
>
> In the tube era circuits tend to take on names related to what's being
> made. In TV circuits you have horizontal sync detectors, which are
> phase locked onto the horizontal sync pulses, and "automatic phase
> control" for the chroma demod. Look at a 'modern' schematic of the
> same thing and you'll see them called PLLs.
So a locked oscilator is a form of PLL?
It don't seem like that to me. In an FM set there is a 19kHz pilot
tone with constant amplitude to lock an oscilator to so getting a
38kHz carrier which can be adjusted with LC circuits to be in phase
with supressed subcarrier L-R signal. But the 38kHz generated can
drift a little, because there is no PLL, and then the stereo
separation suffers at higher AF.
> The modern version of the synchrodyne direct conversion is PLL direct
> conversion. Those things are literally everywhere but the basic
> principle goes back to the synchrodyne which, in turn, evolved from
> the homodyne.
>
> >Its like Multiplex Stereo decoding, no bastard has ever produced a
> >fully tubed version of a Gilbert Cell to get stereo signals from an FM
> >composite signal - they all fall back onto a diode matrix circuit.
>
> It's cheaper and sufficient.
>
> As I've told you a thousand times, cost is *always* a concern and it
> had nothing to do with bean counters who don't know a synchrodyne from
> a dyno-soar.
But I don't have to care about costs where the profits are not having
to be shared by an accountant, marketing&sales team, rent of factory,
CEO supply of Glen Fidich Wiskey, CEO Cadilac, CEO wages, shareholders
and all the others who have to get paid out of sales. My activities
are completely hand crafty one of a kind specials for mainly poor ppl,
like me. Now one might think that in a world of 7 billion ppl there'd
be one or two others who'd be able to tell us how they tried to use 4
x 6DJ8 tubes to make a GIlbert Cell, or a PLL, and get a result as
good as any chip.
Understand my DINO SAW appoach?
>
> >So they say they like to use tubes, but they fuckin' won't, and don't
> >have all the answers.
>
> Just who is the 'they' you are babbling about?
Excellent question. I have no idea who has built a PLL using tubes.
Who ever they are, they are keeping themselves out of the limelight,
and certainly away from giving you any opportunty to tip a bucket of
shit on them.
>
> >At least 5 bjts are needed for a Gilbert Cell, so 5 triodes are needed
> >for a tubes version,
>
> No, because you use 'special' tubes instead of triodes, like the beam
> deflection tubes I told you about way back when you were futzing with
> your transistor Gilbert cell.
But where you can use a bjt, you should be able to use a simple
triode.
>
> > and who wants to use more tubes just for
> >detection than the number used for the rest of the set?
>
> Bean counter.
Depends how many and why and what sort of job is done.
I repeat, the CF detector of mine is lookin' good, so simple and
effective.
And it could improved. The load of the CF could be an RFC and the
diode could just drive a resistance so the output looks like one half
of the modulated envelope shape, and there is no C used. Then the
second CF is used to buffer this to feed to a low pass LC or RC filter
which removes the 455kHz signal entirely and you are lefet with just
the audio content. The conversion efficiency is less, as it is with
the "infinite impedance detector" but linearity of detection should be
excellent.
Patrick Turner.
Patrick Turner
> On Wed, 20 Jul 2011 00:10:06 -0700 (PDT), Patrick Turner
>
> <i...@turneraudio.com.au> wrote:
>
> >> >I'm not planning to build AM radios for ppl with 400+ tubes
>
> >> That's the whole damn radar set, silly, not 'a' PLL.
>
> >Of course. I was yus Yoking.
>
> >> >. 4 tubes
> >> >is about enough, 1 x RF amp, 1 x F converter, 1 x IF amp, and 1 x twin
> >> >triode for the CF detector.
>
> >> Bean counter.
>
> >But all those manufacturers before me used far fewer tubes.....
>
OK, I count tubes, and sure, there's a limit. I offer more than what
companies used to offer. They employed accountants, I don't. I don't
need an accountant to tell me how I waste my talents or time, all of
which are worth money. Just not very much. Not enough business is done
here to warrant the employment of an accountant to advise me about
where all the money goes, and how to limit the flow, thus controlling
design.
> McIntosh did 'more and bigger' than most others too but I assure you
> they also took cost into account. They just had a different market
> strategy.
When McIntosh began, like so many ther companies, they went in with
bucket fulls of investment capital and armed with a reasonably good
idea of an amp. They had good accountants and managers and engineers
and quality control so the success happened.
But while McIntosh beavered away making stuff that cost an arm and leg
for most ordinary low paid folks, a veritable army of others worked
away to make junk for the low income earners, and here the margins
were much lower, and thus saving the cost of one tube with a
production run of 100,000 units meant a large different to a company
bottom line.
snip,
>
> >I'm doing this for part of my living. The labour time I spend on a
> >radio rebuild can be hundreds of hours. I enjoy it, but the pay is
> >maybe $2 an hour.
>
> I was making the point that after gutting and replacing the insides
> it's no longer what they brought to you.
In a 1935 radio I am now re-engineering, the 3 tubes made in Europe in
the 1930s had to be replaced. None are easily available. Two already
had been replaced with Oz made octals. The 1935 speaker IS CRAP. The
lady will like the tube sound using a better circuit and tube types
made between 1945 and 1960. These remain fairly abundant.
>
> Doesn't bother me, much, but I'm sure there are collectors out there
> fuming and ripping out hair at the 'tragedy of it all.
I give my customers what suits their listenig needs, and what suits
their wallets, and what suits their preferences for preservation of
the old circuits. A few just want their gear kept original such as one
guy who wanted his Leak and Quad tube systems kept original. When you
walked into his lounge, an early vinyl would be playing, and deacor
was all exactly like 1955. On the 1955 coffee table, a newspaper
headline screamed "SUEZ BOMBED". One had to pinch oneself to remind
you were really in 2010.
But some have a nice of floor standing cabinet with very attractive
dial which IS SACRED as far as I am concerned. The electronics which
was fitted into such grandiose bits of furniture was often pretty
ordinary, and sub-standard in performance. All I do is make it all
work as IT SHOULD HAVE when new, and I'll include to put terminals for
a CD player. I have ppl wanting me to fix some very junky un-
collectable non valuable old radiograms with very poor TTs. I refuse
to work on some of the worst. Some don't give a stuff about the
cabinet and just want me to rescue the 4W stereo SE amps and re-house
them in a painted plywood box with a tube phono amp for MM TT. So
there is a whole range of things I am asked to do. I have a pair of
Quad-II-Forty which I'll drastically change to a far better circuit in
coming weeks.
So the only tragedy is in your short sighted understanding of what
occupies my life.
> >I often must wind a new OPT about 4 times bigger than the Walnut
> >Acountant model of OPTs which were included in the scam behind the
> >brand name.
>
> Definitely need a 20Hz OPT feeding a 5 inch accordion cone speaker.
> What were they thinking?
But one radio-gram was a Phillips POS with stereo with 2 x 6M5, 2.5W
per channel, and 8" speakers which were broken and in a large cabinet
for good bass. Existing OPTs were fried.
The pair of OPTs I wound went down to 40Hz, but still were much larger
than the very high winding loss types made by fucking Phillips. For
9W, and 20Hz, Afe must be at least 36mm x 36mm. I don't go that far,
and in a small mantle radio, 80Hz is OK and for 2 watts, along with
25% winding losses with hair thin primary wire. I have enough spares
to last me for those types of radios, but not for the big floor
standers which are capable of excellent sound providing OPTs are
bettered along with the circuit function.
In Oz, digital radio which receives signal at over 250Mhz is the new
radio media, and most sets are horrid little boxes, some of which are
retro styles and only capable of terrible sound despite the beautiful
signal quality that is received so I guess in future there's the trade
of making sure old AM sets may be fed with a signal from a digital
radio.
> >> >But If I wanted to make a PLL for AM detection, I guess theory tells
> >> >me I'd have to have circuit to detect the phase difference of the IF
> >> >signal with a 455kHz crystal oscillator,
>
> >> Only if you kept IF conversion.
>
> >Even if I didn't, one still has to have an oscillator track the RF,
>
> Yes, but you don't need to do a conversion.
>
> >and be accurate. DG Tucker's Synchrodyne of 1947 is a difficult thing
> >for anyone to build at home, but at least its tubed, and perhaps could
> >be improved a lot if a couple of modern methods were applied.
>
> Whether it's 'difficult' or not isn't the point. The point was you
> claiming no one did it.
You claimed that, I didn't. I just said a google search on tubed
circuits labelled as PLL brought up fuck all.
Nobody gives a rat's arse about developing tubed circuits it seems.
There is nothing for me or anyone else to build on. Go do your own
R&D, that's what the world tells me.
>
> >But I also like the idea of a 2Mhz IF so that the side band cutting is
> >minimised but it probably requires 6 tuned ciricuits in 3 IFTs to get
> >sufficient skirt selectivity.
> >Just means two IF amps. Same CF detector could be used, but 6DJ8 would
> >be a better tube for the higher F.
>
> The point would be synchronous detection, not to go through that
> rigmarole just to stick the same ole diode on the end of it.
I'd like to think a tubed synchrodne set with PLL could easily be
done, but I'm a realist; no such thing is easy.
> >> > so something like an FM
> >> >discriminator which produces a good swinging DC voltage, which will
> >> >swing enough adjust the variable oscilator in the F converter section
> >> >of the AM radio, and then hold the oscillator F so darn accurate the
> >> >IF and crystal oscillator are dead accurately aligned, without being
> >> >even one wave out.
>
> >> It's called a PLL in modern parlance.
>
> >> It isn't quite the 'miracle' you imply with "so darn accurate,"
> >> although it is.
>
> >In a tube FM set there is often 4 triodes for the RF amp, mixer,
> >oscilator and rmaining triode is for AFC, where the dc from
> >discriminator is applied to the grid of 1/2 a 6AQ8 or 12AT7 to change
> >gm of the triode which changes the C looking into the anode. The
> >slight change of C is enough to swinf F a long way at 100MHz, but not
> >at 455kHz. Its not the same4 as PLL though.
>
> You don't need to 'swing' the PLL far. You *tune* it near the
> frequency and then it pulls lock.
One would think someone has done all with tubes and has it online but
no such thing I could find.
>
> >> You're thinking like proportional error, which would have to be
> >> incredibly small requiring huge gain, but a PLL isn't proportional
> >> "automatic frequency control." �A PLL, or "automatic phase control,"
> >> integrates the difference by comparing phase and because it behaves as
> >> a frequency error integrator the frequency error 'naturally' goes to
> >> 0.
>
> >Well if you know so much about PLL, I guess we can look forawrd to you
> >providing us with a schematic next week.
>
> I've used PLLs before, and even designed them from scratch when the
> 'building blocks' didn't fit my application, but I'm not interested in
> designing an AM radio. Same goes for an internal combustion engine. I
> can tell you how they work too but am not interested in building one
> of those from scratch either. At least not today.
Ah, you don't really give a fuck about the subject anyway.
>
> >> > Trouble is trying to vary oscillator F in tube gear
> >> >and at such LF as 455kHz takes large variations of C in tank circuits,
> >> >and all I could find to do this was a bunch of paralleld 68V zener
> >> >diodes where their C varies like a varicap before you reach the zener
> >> >voltage. Varicaps diodes require very low circuit signal voltages. But
> >> >higher voltage rated zeners allow the kind of voltages seen in tube
> >> >gear - always much higher than in SS junk.
>
> >> Reactance tube.
>
> >Does not do enough at 455kHz.
>
> Prove it.
I did prove it to myself once when I built a 455khz oscillator which
has a wobbulator function to create FM with +/- 40kHz of F deviation
using 10 x parallel 68V zener diodes.
Its possible that Idea could be applied with a circuit which compares
RF input phase and oscilator phase and then the Vdc could swing the F
enough. In old days, a reactance tube was handy, and then the F was
multiplied quite a few times along with the deviation. FM transmitters
using tubes were hellishly complex.
Now all one needs is a BA1404 chip and a 1.5V battery. Something you
clip to your lapel, with two mics for stereo.
>
> >> >But it seems no bastard has ever bothered to spend a month or three to
> >> >get a PLL working for AM reception with tubes.
>
> >> Of course they did. Try looking up synchrodyne.
>
> >>http://www.thevalvepage.com/radtech/synchro/section5/section5.htm
>
> >The schematic there has NO PLL and **IS D.G. Tucker's 1947
> >Synchrodyne** circuit.
>
> Yes, it is Tucker's Synchrodyne and yes it's a PLL.
>
> Go back to RDH4 and read p1227. They describe the classic PLL action,
> albeit in different words. In particular "One advantage of this
> receiver is it is either correctly tuned or not tuned at all." I.E. It
> is 'tuned' when phase locked and not tuned at all if the PLL breaks
> lock. There is no 'in between': classic PLL snap action behavior.
RDH4 has only such a tiny bit of info about synchronous detection, and
no mention of PLL as it is understood in the more modern post tube
world.
There is a pile of references listed for the sychrodyne including
several to Mr D. G. Tucker, but Tucker's schematic does not appear to
be a PLL circuit, although may have a means by whitch AFC control is
good enough to get clean synchronous detection and to stop whistles
during tuning, which RDH4 later refers to below what you quoted.
In Tuckers circuit, V3 is a pentode set up to accept RF from the
broadband front end amps and this RF is applied by V3 cathode to a
winding on the VFO, and so when a strong enough RF signal appeared,
there would be tuning whistles from carrier beating with oscilator
until the RF in became strong enough to synchronise the oscillator as
its F was tuned close enough to the incoming RF. So one could tune a
bit each side of the RF and the oscillator F would stay fixed,
allthogh phase would shift a bit. I guess one tuned it best by sound
quality.
There is no DC amp or very sensitve detection of phase differences
with interfering RF square waves and oscilator square waves. The
Tucker signal would seem to depend on a threshold of RF signal needed
to lock the oscillator, and in 1947, AM modulation rarely went near
100% so there would be enough carrier always present for locking. But
now I see 100% on the CRO all the time from AM stations, and even if
one tries to amplifiy an incoming RF signal with a couple of pentodes
set up like IF limiter tubes in an FM set to ensure no AM exists,
there are times when mod = 100% and the RF limited signal just
dissaprears.
So one must have an oscillator which will "run on" at the locked F for
some time without drift or cessation and controlled by a DC voltage
feeding a an RC circuit with just the right time constant.
Tucker's circuit never caught on. Some say it was before its time. But
when did better AM circuits ever catch on? I see and hear no evidence
anything better ever occured. The vast majority of SS AM/FM tuners
contained AM tuners with 3 bjts, and high Q single tapped coil IFTs
about the size of a pea. The AF BW = 1.5kHz max, andf boosting treble
made no difference because no treble was there to boost. Later they
used even cheaper nastier horribgle 3 pin TRF chips. Audio was
frightful, and on a weak community station of 300W at 1008kHz, some
5km away, I could hear a booming 5kW station also nearby and at
1053kHz. Sometimes I'd get a station from 2,000km away as well. None
such crap happens with a tubed set with well done IFTs.
> Note that you don't need 'conversion' for an IF, to get a 'single
> frequency' for filters, because simply LP filtering the phase
> discriminator does it. That controls the PLL pull in and lock range so
> if it gets 'close enough' to a received carrier it pulls in lock and
> demods.
>
> The theory is great but, as with all things, there are practical
> considerations with the antenna potentially picking up the local osc,
> which is at the same frequency you're trying to receive, being one of
> them. Obviously not a 'good thing' to have happen.
>
> >The main difficulty with the synchrodyne is how to make the ring
> >modulator transformer, amoung other problems.
>
> Tucker managed and so did others.
There is never ever enough info on such trannys now. No How-To-Do. A
radio hame said use a toroid core with proper permeability. I got
nowhere with the ideas. Knowing exactly which toroid RF core to use is
essential. I gave up.
>
> >By the time someone has fucked around with Tucker's circuit one would
> >have better spent the time on a superhet.
>
> Depends on what the bean counter says, eh?
Bean counters sure made sure the Tucker would never be put onto shop
shelving.
> A superhet is sufficient but the synchrodyne is more accurate.
Says he who doesn't really care enough to build anything much.
>
> >> The terminology "Phase lock loop" didn't come about till the 1960s
> >> when integrated circuit 'building blocks' prompted the creation of
> >> more generic 'building block' names.
>
> >Indeed.
>
> >> In the tube era circuits tend to take on names related to what's being
> >> made. In TV circuits you have horizontal sync detectors, which are
> >> phase locked onto the horizontal sync pulses, and "automatic phase
> >> control" for the chroma demod. Look at a 'modern' schematic of the
> >> same thing and you'll see them called PLLs.
>
> >So a locked oscilator is a form of PLL?
>
> A phase locked oscillator is, which is why it's call a "Phase Locked
> Loop."
>
> AFC (if properly identified) is not a PLL since it's oscillator is
> driven by a proportional frequency error signal. It get's arbitrarily
> 'close' (depending on gain), but is not phase locked, and there is
> always some frequency 'error' that's needed to push the oscillator in
> the desired direction.
Indeed, in FM sets the tendency for RF and oscillator tuning to drift
with changes in temperature is well controlled by AFC but still there
is *some drift* but its not enough to matter.
>
> In a phase locked loop the error signal comes from the phase
> difference and 'in lock' the local oscillator frequency is exactly the
> same as the reference with a phase lead/lag error depending on which
> direction the local osc needs to be 'pushed' to stay on frequency.
>
> The difference is in how the error signal is derived. AFC is frequency
> deviation and PLL is phase deviation.
>
> >It don't seem like that to me. In an FM set there is a 19kHz pilot
> >tone with constant amplitude to lock an oscilator to so getting a
> >38kHz carrier which can be adjusted with LC circuits to be in phase
> >with supressed subcarrier L-R signal. But the 38kHz generated can
> >drift a little, because there is no PLL, and then the stereo
> >separation suffers at higher AF.
>
> Why in the world do you take a TV horizontal sync circuit and talk
> about FM demod?
>
> If you take an old TV set with a 'horizontal hold' knob you can see
> the PLL 'phase lock' action. When in lock the picture shifts a bit
> either left or right when you turn the knob as the phase of the lock
> shifts with respect to the incoming video (phase error having to
> 'push' the local osc harder, because you're changing the 'idle'
> frequency, so the phase shifts) but it remains perfectly aligned until
> you turn it far enough and... zap, brrr... the slanty lines suddenly
> appear as the local osc breaks lock and is then free running at a
> significantly 'not right' frequency. Turn the knob back to where the
> PLL can pull ...
Google stops me from replying to more.
There are simpler synchrodynes which use one RF amp with RF tuning
followed by a 6BE6 pentagrid. MUCH simpler than Tucker's set, but I
found that a nightmare to build with very feeble performance.
The tubed Superhet is King, still.
Patrick Turner.
Arny Krueger
"flipper" <fli...@fish.net> wrote in message
news:8reb27t53ivpcuo68...@4ax.com...
> receiver had at least one: the horizontal oscillator/sync.
> In color sets you also have the chroma osc.
<trip down memory lane>
Yes, those had to be in phase with the transmitter's clocks. I remember some
phase detectors in the old NTSC sets - an instant tip-off that there was
some kind of phase locked oscillator in play.
Don Pearce
wrote:
This is where PAL really won out over NTSC. Each alternate line the
chroma phase leads or lags by 45 degrees, and the PLL locks to the
average - which is true phase. The result is that when there is an
overall phase error in the chroma signal, alternate lines lead and lag
the proper phase. Add them together and the error vanishes. With NTSC
a phase error means a wrong colour.
d
John Byrns
Patrick Turner <in...@turneraudio.com.au> wrote:
>
> Google stops me from replying to more.
>
> There are simpler synchrodynes which use one RF amp with RF tuning
> followed by a 6BE6 pentagrid. MUCH simpler than Tucker's set, but I
> found that a nightmare to build with very feeble performance.
>
> The tubed Superhet is King, still.
Patrick,
No reason we can't combine the tubed superheterodyne with a tubed synchronous
detector.
I have a few thoughts on PLL detectors, and AM broadcasting modulation depth.
Take my comments with a few grains of salt as I have little expertise in either
of these fields, although one of my PLL designs did make it into a commercial
product, possibly sold in the millions, some in this group, at least when it was
larger may even have used my PLL. However just because I got a PLL into
production doesn't mean that I had a clue what I was doing.
First some thoughts on PLLs.
Injection locked oscillators, as used in Tucker's Synchrodyne Receiver, are not
PLLs in my book, how could they be as there is no loop involved.
The system used in many old FM tuners to stabilize the local oscillator, using
the output of a frequency discriminator to control a VCO, often called "AFC" is
not even a FLL, or Frequency Locked Loop, it is however a loop which reduces
frequency error.
Next in the pecking order is the FLL, or Frequency Locked Loop. This loop
replaces the frequency discriminator with a phase detector which compares the
VCO frequency with a reference such as a crystal oscillator or some other
signal, such as the IF singal, to be locked to. This loop locks the frequency
of the VCO to the frequency of the "reference" but there will be phase error,
which is necessary to create the error signal to control the VCO. While the
frequency is locked, the phase may vary and is not locked, so calling this
common loop a PLL is somewhat of a misnomer, as the phase is variable and is not
locked. This may be what the experts call a first order PLL.
Next in the pecking order is what I will call the true PLL, or Phase Locked
Loop. This is similar to the FLL circuit described above, with the addition of
an integrator circuit between the output of the phase detector and the VCO
control input. The phase error drives the integrator to the voltage level
necessary to put the VCO on frequency and with zero phase error. When the phase
error reaches zero the integrator stops integrating at the voltage level
required by the VCO, if a phase error again develops for any reason, the
integrator level changes to correct it. This loop may be what the experts call
a second order PLL.
You said "the main difficulty with the synchrodyne is how to make the ring
modulator transformer." This doesn't seem like it should be a major problem,
especially for a transformer expert like you. I would think an ordinary IFT
could be pressed into service here, deleting the original secondary and winding
a new low impedance secondary directly over the primary, the outside of which
becomes the cold end of the primary.
My concept of the synchronous detector in this discussion, was using a phase
detector to compare a local VCO with the incoming IF frequency in a PLL circuit.
A second "phase detector" with the local oscillator signal delayed 90 degrees
would be used to recover the audio. In this scheme the local oscillator "VCO"
would always operate at approximately 455 kHz, so that the reactance change
required of the reactance tube is minimal, as there is no need to provide the
10:1 reactance ratio that would be required if the synchronous detector operated
at the received frequency.
For the less ambitious Tucker's "synchronous" detector could be operated at the
IF frequency, eliminating the need for PLLs and multiple quadrature phase
demodulators as used in my scheme.
Modulation depth of AM broadcast transmitters is an interesting subject.
Typically the modulation monitor is connected to the output of the transmitter,
in some transmitters a sample of the output voltage is provided for the monitor,
while in other transmitters a sample of the transmitters output current is
provided. Since the impedance of the transmission line/antenna system is not
constant across the broadcast channel the actual carrier and sideband power
supplied to the transmission line will vary with frequency. Assume that the
transmitter provides a current sample to the modulation monitor and that the
resistance seen by the transmitter at the input to the transmission line
increases at the sideband frequencies. Assuming that the modulation monitor is
reading 100% the actual sideband power radiated by the antenna will be greater
than what is required for 100% modulation, and a radio receiving the signal
radiated by the broadcast antenna will see greater than 100% modulation, even in
the negative direction, causing problems for envelope detectors including the
pseudo synchronous detectors. A true synchronous detector will be immune to
this type of over modulation. If the transmission line resistance varies in the
opposite way the situation will be reversed and the radio will see lower
modulation than the station thinks it is using. Voltage sensing for the
modulation monitor will reverse all the above conditions, as will an extra
quarter wave length of transmission line between the transmitter and antenna
will invert the impedance, again reversing all the conditions accordingly. Also
the impedance seen by the transmitter may be asymmetrical, causing the amplitude
and phase of the two sidebands to be unequal, again resulting in distortion with
envelope detectors, which true synchronous detectors will ignore. Finally,
perhaps the biggest distortion problem is caused by directional antennas which
are nearly universally used in the US, but may not be as widely used in OZ. The
radiation pattern of directional broadcast antennas may be considerably
different at the sideband frequencies than at the carrier frequency, again
resulting in considerable over modulation in some areas, particularly in the
areas around the direction of the antennas nulls. This effect can often be
observed by driving around or past a directional broadcast antenna while
listening to the automobile radio. This is just a simple minded overview, by
someone who doesn't know what he is talking about, to give some flavor to the
many factors involved in determining the actual modulation seen by the radio
receiver in your lounge.
Many of these factors can cause the modulation to exceed 100% negative at the
antenna of your radio, or can cause an asymmetrical sideband situation, either
of which will cause distortion in a simple envelope detector, or even a pseudo
synchronous detector. A true synchronous detector will be immune to the
distortion from these causes, resulting in a more pleasing listening experience.
Many of the AM stereo demodulator chips used in the days of AM stereo used a
pseudo synchronous envelope detector during tuning to eliminate all the squawks
and whistles, and then switched over to a true synchronous detector once the
signal was correctly tuned. So it would seem there is room for both a Turner CF
detector and a true synchronous detector in our tubed radios.
--
Regards,
John Byrns
Surf my web pages at, http://fmamradios.com/
Patrick Turner
> In article <7e22910a-e60e-4a6e-8472-8cd104b14...@28g2000pry.googlegroups.com>,
> Patrick Turner <i...@turneraudio.com.au> wrote:
>
>
>
> > Google stops me from replying to more.
>
> > There are simpler synchrodynes which use one RF amp with RF tuning
> > followed by a 6BE6 pentagrid. MUCH simpler than Tucker's set, but I
> > found that a nightmare to build with very feeble performance.
>
> > The tubed Superhet is King, still.
>
> Patrick,
>
> No reason we can't combine the tubed superheterodyne with a tubed synchronous
> detector.
Except that it is difficult to do as easily as a superhet, even with a
locked oscillator operating at 455kHz.
One would still get lots whistles while tuning until synchronisation
occurs. VFO F - RF is an IF frequency away from 455kHz and is only on
455kHz or close to it when maximum IF gain is achieved at the tops of
selectivity curves. I've had nuerous hetero sets which self oscilate
at 455kHz or therabouts ths causing all sorts of tuning bothers and
noise.
>
> I have a few thoughts on PLL detectors, and AM broadcasting modulation depth.
> Take my comments with a few grains of salt as I have little expertise in either
> of these fields, although one of my PLL designs did make it into a commercial
> product, possibly sold in the millions, some in this group, at least when it was
> larger may even have used my PLL. However just because I got a PLL into
> production doesn't mean that I had a clue what I was doing.
>
> First some thoughts on PLLs.
>
> Injection locked oscillators, as used in Tucker's Synchrodyne Receiver, are not
> PLLs in my book, how could they be as there is no loop involved.
That was my point to Flipper. RDH4 does not talk of PLL.
>
> The system used in many old FM tuners to stabilize the local oscillator, using
> the output of a frequency discriminator to control a VCO, often called "AFC" is
> not even a FLL, or Frequency Locked Loop, it is however a loop which reduces
> frequency error.
I agree. The AFC with one triode does make for much less drift after
turning on a set, tuning to a station while the components are still
cold. So much so that the set stays tuned for days with little drift
even after turning off, allowing everything to cool, then turning back
on.
>
> Next in the pecking order is the FLL, or Frequency Locked Loop. This loop
> replaces the frequency discriminator with a phase detector which compares the
> VCO frequency with a reference such as a crystal oscillator or some other
> signal, such as the IF singal, to be locked to. This loop locks the frequency
> of the VCO to the frequency of the "reference" but there will be phase error,
> which is necessary to create the error signal to control the VCO. While the
> frequency is locked, the phase may vary and is not locked, so calling this
> common loop a PLL is somewhat of a misnomer, as the phase is variable and is not
> locked. This may be what the experts call a first order PLL.
>
> Next in the pecking order is what I will call the true PLL, or Phase Locked
> Loop. This is similar to the FLL circuit described above, with the addition of
> an integrator circuit between the output of the phase detector and the VCO
> control input. The phase error drives the integrator to the voltage level
> necessary to put the VCO on frequency and with zero phase error. When the phase
> error reaches zero the integrator stops integrating at the voltage level
> required by the VCO, if a phase error again develops for any reason, the
> integrator level changes to correct it. This loop may be what the experts call
> a second order PLL.
That is my understanding of the modern PLL, and a number of chips are
supposed to do that.
>
> You said "the main difficulty with the synchrodyne is how to make the ring
> modulator transformer." This doesn't seem like it should be a major problem,
> especially for a transformer expert like you.
I'm like the guy who is a brain neurosurgeon. Get me to work on an
arsole, and I'm dangerous.
Just because I work on AF trannys don't mean I have any experience at
RF. So many ppl want me for my expertise at AF I have not had enough
time to move up the band.
> I would think an ordinary IFT
> could be pressed into service here, deleting the original secondary and winding
> a new low impedance secondary directly over the primary, the outside of which
> becomes the cold end of the primary.
If only it were that simple. It seems to me the untuned coil inductive
reactance would need to be say 10k at the lowest F and with very low
self capacitance > 10pF to be able to be driven with a CF tube so if
lowest F = 455kHz, then L = 3.4mH, which is a lot more than say 200uH
needed for an AM input coil to resonate with a 36-400PF tuning gain.
Perhaps I could use a solenoid coil on a 25mm former with ferrite rods
placed inside the former, and using some solid core telephone hook up
wire which has 0.1mm plastic insulation which spaces the wires to keep
self C low. I just used such a coil for an AM RF input coil which gave
excellent results, and maybe I needed 45t for 200uH, but for 3,400uH
I'd need propably maybe at least 5 times the turns, but working stuff
out for RF is not my forte.
Working with litz wire is a complete PITA. its mainly used to reduce
RF resistance to get the tuned Q of a tank high for F between say
50kHz and 2MHz. Above that F the turns needed for a coil are less, so
solid wire is OK.
>
> My concept of the synchronous detector in this discussion, was using a phase
> detector to compare a local VCO with the incoming IF frequency in a PLL circuit.
> A second "phase detector" with the local oscillator signal delayed 90 degrees
> would be used to recover the audio. In this scheme the local oscillator "VCO"
> would always operate at approximately 455 kHz, so that the reactance change
> required of the reactance tube is minimal, as there is no need to provide the
> 10:1 reactance ratio that would be required if the synchronous detector operated
> at the received frequency.
And in other words so everyone can understand, you meant to
say...................................................., and the
schematic may be found at www....................................here.
Please fill in the blanks for everyon'es benefit.
>
> For the less ambitious Tucker's "synchronous" detector could be operated at the
> IF frequency, eliminating the need for PLLs and multiple quadrature phase
> demodulators as used in my scheme.
I recall I tried trying to use a locked oscilator at 455kHz, but had
so many bothers I gave that idea up too.
There is such a thing as "elevated carrier detection" where a square
wave at the carrier F or IF is added to the incoming RF or IF and the
modulation % is effectively converted to a much smaller %, and the
wamted signal is also "raised up out of the noise" and a detector such
as mine is then used to get almost distortionless AF recovery because
the RF/IF ripple voltage amplitude remains at a constant level during
each AF wave without any flattening or slight cutting off near 100%
mod. The flats created by mod over 100% mod occur with the same shape
as seen on incoming RF/IF which has more than 100%.
AFAIK, some directional AM antennas are used here and I have no idea
what AF distortion they cause. But most AM stations are close to town
and give plenty of level and low THD with 9kHz BW -- If the set is
capable of low THD wide BW, and 95% just ain't.
Digital radio will spread to regional areas as time goes by. Time in
regional areas is much slower than time in big cities, as you should
know, and the further you get from big cities, the less time seems to
happen and its not uncommon to see a small town clock stuck on
12:30pm, and its been like that for years. I now such a clock and
nothing happens there. People are virtually un-alive. But they serve a
very nice coffee and sweetcake. They stopped letting time pass, and
it's done 'em the world of good. Stuff that happens in big cities
often never happens in small towns. The only time when time will
passes in Twelve Thirty is if an ageing pidgeon crashes into the
minute hand on the town clock.
>
> Many of these factors can cause the modulation to exceed 100% negative at the
> antenna of your radio, or can cause an asymmetrical sideband situation, either
> of which will cause distortion in a simple envelope detector, or even a pseudo
> synchronous detector. A true synchronous detector will be immune to the
> distortion from these causes, resulting in a more pleasing listening experience.
That's rather difficult to verify.
>
> Many of the AM stereo demodulator chips used in the days of AM stereo used a
> pseudo synchronous envelope detector during tuning to eliminate all the squawks
> and whistles, and then switched over to a true synchronous detector once the
> signal was correctly tuned. So it would seem there is room for both a Turner CF
> detector and a true synchronous detector in our tubed radios.
In 11months, 2 weeks, 15 hours and 14 minutes time, I turn 65 and can
retire on the old age pension. It will be a great relief not to have
to work for the Greatly Ungrateful Fuckin Masses Who Pay Fuckin
Peanuts for me to repair their bloody awful generic crap they bring
me. I might then have time for spending more days and daze and daiz
and deighs working out what might have been done back in about 1950
for the 2% of the General Public willing to pay more for better
performance.
Patrick Turner.
John Byrns
flipper <fli...@fish.net> wrote:
> On Wed, 20 Jul 2011 19:01:30 -0500, John Byrns <byr...@sbcglobal.net>
> wrote:
>
> >First some thoughts on PLLs.
> >
> >Injection locked oscillators, as used in Tucker's Synchrodyne Receiver, are
> >not
> >PLLs in my book, how could they be as there is no loop involved.
>
> By golly I think you're right. I first thought he was using phase from
> the mixer but upon closer inspection I see I got turned around in the
> wiring loops.
>
> Amusingly enough, though, injection locking can be modeled as a first
> order PLL so the net result is conceptually the same.
Sounds right, I'll buy that.
>
> Not being an RF engineer I could be wrong but for AM demod we don't
> really give a hoot about phase, do we?
I believe we do care about phase, and I don't think we need look any further
than our old High School Trigonometry books to find out why, no RF engineering
expertise required. IIRC the AM equation goes something like this, sin(wct) *
(1 + sin(Wmt)). If we multiply this by a locally generated copy of sin(Wct) in
the receiver we get ((sin(wct))^2) * (1 + sin(Wmt)). Without getting out my
aforementioned High School Trigonometry book, I think ((sin(wct))^2) = 0.5 + 0.5
sin(2Wct) or something like that. The 0.5 term multiplied by sin(Wmt) gives us
back our original modulation.
If we try to use a quadrateure carrier in the receiver, i.e. cos(Wct) so that we
have cos(Wct) * sin(wct) * (1 + sin(Wmt)), and IIRC, without getting out the
book, cos(Wct) * sin(wct) doesn't include a DC term, only a sin(2Wct) term,
without the DC term we don't get demodulation of the desired signal, just
quadrature noise. Local carrier phase angles between sin(Wct) and cos(Wct) will
produce some DC, although less than an in phase carrier, so the demodulated
signal will be attenuated relative to an in phase carrier, and it will be full
of quadrature noise that is demodulated by the cos(Wct) component of the locally
generated carrier.
Patrick Turner
> In article <0n3f27d3d7t9hds3ngeopocknqpo8ko...@4ax.com>,
explanation has delivered a perfect understanding of how to write two
paragraphs which are totally incomprehensible, and thus offer Sweet
Phark All information about how to build a better AM detector.
Whatever John was trying to say remains pure and detailed, and
meaningful to someone@somewhere while remaining 100% fully obscure.
There was a man with a radio,
who used just one cat's whisker,
He prodded the crystal, the cat went beserk,
So that idea couldn't be sillier.
Patrick Turner.
Patrick Turner
> On Thu, 21 Jul 2011 21:38:45 -0500, John Byrns <byr...@sbcglobal.net>
> wrote:
>
>
>
>
>
> >In article <0n3f27d3d7t9hds3ngeopocknqpo8ko...@4ax.com>,
>
> >> On Wed, 20 Jul 2011 19:01:30 -0500, John Byrns <byr...@sbcglobal.net>
> >> wrote:
>
> >> >First some thoughts on PLLs.
>
> >> >Injection locked oscillators, as used in Tucker's Synchrodyne Receiver, are
> >> >not
> >> >PLLs in my book, how could they be as there is no loop involved.
>
> >> By golly I think you're right. I first thought he was using phase from
> >> the mixer but upon closer inspection I see I got turned around in the
> >> wiring loops.
>
> >> Amusingly enough, though, injection locking can be modeled as a first
> >> order PLL so the net result is conceptually the same.
>
> >Sounds right, I'll buy that.
>
> injection locked LC oscillators to see 'why'.
>
> Maybe no one cares but I found it interesting and can conceptually see
> that the 'phase comparator' and VCO 'loop' are subsumed, or 'hidden',
> in the process. A 'PLL expert' would probably instantly see it in the
> math.
>
> The basic 'frequency changing' mechanism is similar to how a reactance
> tube works. I.E The 'injected' signal forces a shift in the tank
> (current/voltage) phase, which forces the tank to change frequency in
> order to reestablish proper phase. Our 'VCO'.
>
> In the case of the typical reactance tube application the tube is run
> at a fixed phase offset and the amount of tank 'upset' is due to how
> much of it is injected, by modulating the grid. The VCO 'control
> input'.
>
> In this case, however, the amount of tank 'upset' will be proportional
> to the LO-RF phase difference, so it acts a phase comparator. I.E. If
> they are in phase then there is no (current/voltage) tank upset, and
> no change to tank frequency, but there must be 'some change' when the
> LO is not at the right frequency, so there must be a phase difference
> to 'hold' the tank on frequency. That's a first order PLL.
>
> If we built it the conventional 'separate piece for each function' way
> we'd have a separate phase detector, filter, and reactance tube VCO.
> Those functions are still there, albeit hidden, in the injection lock
> but we have much less control over the parameters. Like the reactance
> tube circuit it also depends on injection amplitude so AM should cause
> phase jitter we have no convenient way to filter or control and, of
> course, there's no 'free wheeling' across 0 carrier, not to mention we
> can't add an integrator. I mean, since it's all subsumed in the
> process itself we don't have a lot of filtering choices like with
> separate components..
>
> Does imply the thing might be better with a separate RF limiter before
> the injection lock, though.
>
> Or do a proper 'separate pieces' PLL, like I mistakenly thought he
> had. Speaking of which, I consider Tucker's injection lock to be
> 'proof' that a reactance tube VCO would have enough range since they
> are reducible to the same thing. You only need enough lock range for
> the channel width with 'getting close enough' being what the station
> tuning knob is for (antenna tank and VCO Fo).
>
> As a side note, for further entertainment, while searching for the
> injection lock papers I also ran across one on an "injection locked
> PLL" where the phase detector and 'VCO' functions for what is
> explicitly called a "PLL" are also subsumed inside the oscillator so
> you have the rather amusing case where a 'hidden' PLL is called
> injection locked but the other 'hidden' PLL is called a PLL.
>
> >> Not being an RF engineer I could be wrong but for AM demod we don't
> >> really give a hoot about phase, do we?
>
> >I believe we do care about phase, and I don't think we need look any further
> >than our old High School Trigonometry books to find out why, no RF engineering
> >expertise required. IIRC the AM equation
>
>
>
>
>
>
> > goes something like this, sin(wct) *
> >(1 + sin(Wmt)). If we multiply this by a locally generated copy of sin(Wct) in
> >the receiver we get ((sin(wct))^2) * (1 + sin(Wmt)). Without getting out my
> >aforementioned High School Trigonometry book, I think ((sin(wct))^2) = 0.5 + 0.5
> >sin(2Wct) or something like that. The 0.5 term multiplied by sin(Wmt) gives us
> >back our original modulation.
>
> >If we try to use a quadrateure carrier in the receiver, i.e. cos(Wct) so that we
> >have cos(Wct) * sin(wct) * (1 + sin(Wmt)), and IIRC, without getting out the
> >book, cos(Wct) * sin(wct) doesn't include a DC term, only a sin(2Wct) term,
> >without the DC term we don't get demodulation of the desired signal, just
> >quadrature noise. Local carrier phase angles between sin(Wct) and cos(Wct) will
> >produce some DC, although less than an in phase carrier, so the demodulated
> >signal will be attenuated relative to an in phase carrier, and it will be full
> >of quadrature noise that is demodulated by the cos(Wct) component of the locally
> >generated carrier.
>
> mixer in there.- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
Perhaps you are seeing more about how a locked oscillator works.
In practice, a locked oscillator produces a constant amplitude of
identical frequency to the RF input which needs to be over a threshold
to ensure locking, ie, synchronisation. But if the incoming RF is
modulated then the oscillator signal phase relative to RF signal which
we wish to demodulate becomes phase modulated
which gives unwanted IMD effects. So the RF signal fed to the locked
oscillator is ideally a highly limited sample of the RF signal derived
from the receiver front end.
But when 100% modulation occurs, the RF signal reduces to zero, and no
synchronization is possible, and the oscillator drifts straight off
the RF carrier F.
But while the oscillator is locked, slight tuning each side of the
"center frequency" alters the RF carrier to oscillator phase and it
can be aatered to virtually zero which we might say is where the sound
output will be greatest and best sounding.
Then there are other bothers with synchrodyne selectivity. Usually
most RF front ends on radios have at least one tuned LC tank which
would track the tuning of the VFO. But Tucker's set just has a pass
band and everything comes in, and so just what sort of selectivity and
freedom from monkey chatter and other effects one gets is not clear.
The superhet overcomes most problems one has when trying to build a
Tucker circuit.
Just why did nobody bother to commercially produce a Tucker
Synchrodyne radio in the 1950s? I'm sure a lotta experimenty ppl must
have tried, and I'm sure they mostly failed for a variety of reasons,
and they'd have wasted days if not weeks trying to get the damn thing
to stop making whistles and noises and then give sound as good as a
well done superhet.
All the synchrodyne radio circuits I have on paper files have RF
tuning on their front end RF amps.
Here is a brief list of what I have, which by now may have been put
online by someone somewhere, or by nobody anywhere :-
Ideas for the inventor ETI Feb 1980, a synchrodyne with ferrite rod
antenna, one 415pF tuning cap, one mosfet in cascode with bjt for RF
gain, then a standard FM detector and limiter chip such as LM2111,
MC1351, LM1841, and several others similar. Works off +/-9Vdc.
Radio, Television & Hobbies, Sep 1963, by Ian Pogson, Synchrodyne AM
tuner. Uses 6EH7 RF amp with only input tank, tuned by one gang of 2
gang cap.Has 6BE6 VFO with LC tuned by the second gang. Has LCLC low
pass filter for audio output from 6BE6 anode. Very simple. AF is -3dB
at 10kHz!
Synchrodyne AM Receiver by Linsley Hood, Part 2, Electronics and
Wireless World, Feb 1986. Part 3 in March 1986. Has fiendishly complex
circuit needing very cafeful PCB board desugn using GENUINE PLL with
MC1496 phase detector, TLO71 dc amp, varicap diode to control
oscillator F. Enormous expertise needed to reproduce such circuits.
Synchronous Detection in Radio Reception - 1, by Pat Hawker, Wireless
World, Sep 1972, part 2 Nov 1972. Lots of explanations about Tucker's
efforts, then lots of discrete SS devices used in schematics shown.
Extremely complex schematics shown alongside some simple types, all
SS.
A Homodyne Receiver by J W Herbert, Wireless World, Sep 1973, Not very
complex, uses CA3028A plus MC1330P, dedicated for broadcast band, but
has tuning by a pair of ganged variable inductors.
Patrick Turner.
Arny Krueger
"Don Pearce" <sp...@spam.com> wrote in message
news:4e270cf4...@news.eternal-september.org...
>>Yes, those had to be in phase with the transmitter's clocks. I remember
>>some
>>phase detectors in the old NTSC sets - an instant tip-off that there was
>>some kind of phase locked oscillator in play.
> This is where PAL really won out over NTSC. Each alternate line the
> chroma phase leads or lags by 45 degrees, and the PLL locks to the
> average - which is true phase. The result is that when there is an
> overall phase error in the chroma signal, alternate lines lead and lag
> the proper phase. Add them together and the error vanishes. With NTSC
> a phase error means a wrong colour.
NTSC = Never The Smae Color Twice. ;-)
West German color TV was PAL, right?
When I was there in the late 60s, the color was IMO better and more
consistent than NTSC was at that time.
With *only* about another 20 years of development, NTSC became generally
quite stable and generally looked good by the 80s. ;-)
Don Pearce
wrote:
>
And now it is all digital, so no longer matters. Actually Germany was
PAL B/G, while UK was PAL I. The only real difference was in the
luminance bandwidth, which was a fair bit wider in PAL I. Better
horizontal resolution was the result.
I should have added that the two adjacent lines' chroma signals were
added together by means of a delay line. This happened in good quality
TVs. In cheap ones, almost the same effect was obtained visually by
the lines being close enough together to effectively merge on screen.
Poor beam focus helped enormously.
d
Patrick Turner
> http://www.thevalvepage.com/radtech/synchro/section5/section5.htm
>
> However, from what the reprint says, Tucker was not trying to make a
> 'radio'.
But it was a radio, damn it.
>
> > and so just what sort of selectivity and
> >freedom from monkey chatter and other effects one gets is not clear.
> >The superhet overcomes most problems one has when trying to build a
> >Tucker circuit.
>
> And the Tucker circuit overcomes problems with the superhet.
I am not so sure it does.
The superhet offered very good selectivity at the cost of audio
bandwidth, but you could make a superhet with wide AF BW. Makers just
didn't, because they'd successfully got people addicted to low AF BW
whichsuited bean counters.
AFTER you've tried to make a synchrodyne successfully, then see what
you think.
>
> Neither are 'perfect' and I didn't present it as 'perfect'. It was
> intended to be an example and 'aid' to your quest, not a hobby
> construction kit.
Indeed that's true.
>
> >Just why did nobody bother to commercially produce a Tucker
> >Synchrodyne radio in the 1950s?
>
> For one, because it isn't a 'radio'. Second it has, at least in raw
> form, some consumer irritating aspects. And, probably most important,
> it costs more than a superhet which has flawed but, nevertheless,
> satisfactory performance.
But it IS a radio.
>
> > I'm sure a lotta experimenty ppl must
> >have tried, and I'm sure they mostly failed for a variety of reasons,
> >and they'd have wasted days if not weeks trying to get the damn thing
> >to stop making whistles and noises and then give sound as good as a
> >well done superhet.
>
> So does a SSB receiver but people discovered how to make squelch
> circuits.
Sure, but communications radio techniques are all mainly utterly
unacceptable for Joe Punter, who wants excellent broadcast sound at
the flick of a switch, and different stations by turning one knob,
with no noises. So all the fancy techniches used to comm radio are
irrelevant, because they focus on using small level signals to be able
to be recieved in a crowded band fulla noise.
>
> Tucker's original already has the beginnings of one possible solution
> with the 'tuning indicator' (which, btw, is the beginnings of a second
> order PLL). I.E. MUTE the darn thing when off tune. That, of course,
> adds complexity so see third reason above.
Indeed the mute was needed to block loud whistles when tuning.
Today we'd use touch tuning in 10kHz steps in US or 9kHz here. The
oscillator F is selected, not tuned with LC.
If one wanted to, one probably could use an SS step tuned oscilator
for use in a tubed superhet or synchrodyne. AM Stations here are all
expected to have accurate station frequencies at 9kHz along the AM
band and in fact there's no need for mechanical tuning. The type of
oscillator won't affect the sound quality.
>
> But I thought you were all for the 'absolute best' instead of being a
> 'bean counter'.
The absolute best cannot contain more tubes than it has to.
And no less than it has to.
I don't need to employ a bean counter.
> I'm sure they're interesting but without the articles they're not much
> else.
But these things were leading edge thoughts on radio design in their
day. You have not told me how your construction progress is proceeding
on anything better than in all those articles by greater minds than
yours.
>
> You seem to think that PLLs, double balanced mixers, and direct
> conversion are all 'failed' concepts but they're all over the place,
> like every cell phone to name but one incredibly common application.
>
> They became 'uber cheap' with integrated circuits but there's no
> reason variations of the same techniques can't be applied with tubes.
I didn't say the ideas failed; I just said Synchrodyne radios failed
to be manufactured because superhets were easier and cheaper.
Trying transfer ideas used in mobile telephone chips to tubes is often
virtually impossible, just making a Gilbert Cell needs about 4 twin
triodes so just to do one function tales as many tubes as have been
used in a complete tube radio. Mobile phones sound dreadful.
>
> Amusingly enough, the injection locked oscillator you seem to disdain
> also seems to be all the rage these days.
>
> If I were so inclined I'd probably look for some pre-made diode ring
> mixers to avoid the misery of trying recreate that wheel.
>
> Now, here's one that's interesting, the Injection locked PLL I
> mentioned earlier
>
> http://my.ece.ucsb.edu/yorklab/publications/biobib/114%20-%20mtt%20au...
>
> It uses a FET but that should be tube transferable.
The schematic is figurative, and can't be built from info offered. It
is als designed for 10GHz.
But probably varying a triode's bias current would change F a bit.
There are a number of reactance tube tuners around.
>
> I'd still tune with an LC, for the same kind of 'Tucker' injection loc
> and 'wide tuning range' (with the 'big mechanical cap'), and see if I
> could somehow duplicate the second order PLL function with the
> varactor(s), like they did, since that has to pull only enough to
> bring phase in lock.
>
> Or I'd just use a reactance tube and make a 'proper' PLL loop with it
> but that might take a second limited mixer to get the AM off it.
> That's what makes the ILPLL interesting since it uses the gain element
> as a mixer so you'd just need to use an RF limiter for the injection.
I recall making a limiter like that used in a tubed FM radio 10.7MHz
IF strip. You set up a 6AU6 so it spends its life grossly overloaded,
and anode current is just basically square waves, so very little input
signal is need for that, especially if you have two such simple tube
stages cascaded. But still you get drop out on 100% mod peaks. The
changes in carrier F are faithfully preserved during such techniques.
The better way to make a syhchronous AM radio with only as many tubes
as needed for signal handling is to use a digital controller for
oscillator F. These have been around for 30+ years. You get push
button tuning. One could have push button oscillator tuning and then
have input RF tuning with conventional tuning gang.
One could even have a switchtable set of say 12 preset frequencies
with 12 variable preset caps. One could copy part of what has been
done already in many push button type AM/FM tuners.
I'd prefer to used ganged tuning caps and have a muting device which
turns off when lock is achieved. That would be easy with a some
discrete bjts. Although I like green eyed tube tuning indicators, a
meter or row of LEDS is just as good.
Patrick Turner.
Don
Don Pearce
wrote:
>Don't forget SECAM, System European, and Contrary to Any other Method
The French. Says it all, really.
d
John Byrns
Patrick Turner <in...@turneraudio.com.au> wrote:
> > http://www.thevalvepage.com/radtech/synchro/section5/section5.htm
> Today we'd use touch tuning in 10kHz steps in US or 9kHz here. The
> oscillator F is selected, not tuned with LC.
> If one wanted to, one probably could use an SS step tuned oscilator
> for use in a tubed superhet or synchrodyne. AM Stations here are all
> expected to have accurate station frequencies at 9kHz along the AM
> band and in fact there's no need for mechanical tuning. The type of
> oscillator won't affect the sound quality.
Perhaps not for you, however different oscillators have different amounts of
sideband noise that can degrade RF performance of the radio, and some people
with good hearing may be sensitive to the artifacts introduced by different
types of oscillators.
> > But I thought you were all for the 'absolute best' instead of being a
> > 'bean counter'.
>
> The absolute best cannot contain more tubes than it has to.
>
> And no less than it has to.
That's a little vague; it sounds like the number of tubes needed is subjective?
> > You seem to think that PLLs, double balanced mixers, and direct
> > conversion are all 'failed' concepts but they're all over the place,
> > like every cell phone to name but one incredibly common application.
> >
> > They became 'uber cheap' with integrated circuits but there's no
> > reason variations of the same techniques can't be applied with tubes.
>
> I didn't say the ideas failed; I just said Synchrodyne radios failed
> to be manufactured because superhets were easier and cheaper.
>
> Trying transfer ideas used in mobile telephone chips to tubes is often
> virtually impossible, just making a Gilbert Cell needs about 4 twin
> triodes so just to do one function tales as many tubes as have been
> used in a complete tube radio. Mobile phones sound dreadful.
I think the point was that many cell phones use direct conversion receivers,
which is essentially what we are talking about here. In the case of cell phones
the radio handles digital data, not analog signals, and the low rate digital
speech coders used are the reason for the dreadful sound. There are apparently
łHD˛ cell phones available now in some countries that use higher bit rates and
łbetter˛ speech coders. What we are talking about is using direct conversion
receivers to demodulate good old analog AM, not digital data, so the dreadful
mobile phone sound is irrelevant. Direct conversion receiver concepts are
easily transferable to tubes.
> The better way to make a syhchronous AM radio with only as many tubes
> as needed for signal handling is to use a digital controller for
> oscillator F. These have been around for 30+ years. You get push
> button tuning. One could have push button oscillator tuning and then
> have input RF tuning with conventional tuning gang.
Using ła digital controller for oscillator F˛ doesn't give you a synchronous AM
radio, you still need a synchronous detector with some kind of PLL or injection
locked oscillator, whether it operates at the RF or IF frequency.
Alex Pogossov
I do not know why the French preferred SECAM to PAL, but for the Russians
the answere was obvious. The thing is, colours in SECAM are *least* affected
by nonlinearity of amplitude/phase response of the signal chain (around the
colour subcarrier(s), which are two in SECAM).
For example, in the direct vicinity of a TV station a good NTSC TV set will
potentially give the best picture quality, because colour demodulation is
linear, and each line is independent. PAL will be the second because of
averaging of two lines, and SECAM the worst because FM colour subcarrier
modulation inherently is limited by slew rate, and colour transitions are
not that sharp.
And now suppose you pass your TV signal through a couple of analogue
radio-relay links. Each would introduce a significant phase shift (up to
+/-45deg), especially the Russian ones, where everything electronic was of
inferior quality.
NTSC will lose its colour completely.
PAL will preserve colour, but will lose saturation or the colours will be
"pulsating" because of phase jitter.
SECAM will still show correct well saturated colours. Not surprising,
because though phase might be unstable intermittently, the frequency on
average does not change. The colours will be more noisy (phase
jitter-->frequency jitter), transitions will not be as crisp (like the
picture will be rather coloured than colour), but on large areas the colour
reproduction and saturation will be the same as in the original studio
material.
No wonder the Russians in those days chose SECAM because vast size of the
country assumed lots of radio-relay links.
Now when everything is digital and satellite, PAL is the most common in
Europe and better than SECAM, and Russia switched to PAL.
Patrick Turner
> On Fri, 22 Jul 2011 18:27:12 -0700 (PDT), Patrick Turner
>
> <i...@turneraudio.com.au> wrote:
>
> >>http://www.thevalvepage.com/radtech/synchro/section5/section5.htm
>
> >> However, from what the reprint says, Tucker was not trying to make a
> >> 'radio'.
>
> >But it was a radio, damn it.
>
> intended trumps yours.
Well I don't mind much about being trumped by a bloke who knew +20dB
more than I do about radio sets. But for me and thousands of others, a
Tucker Synchrodyne = radio, right?
>
> >> > and so just what sort of selectivity and
> >> >freedom from monkey chatter and other effects one gets is not clear.
> >> >The superhet overcomes most problems one has when trying to build a
> >> >Tucker circuit.
>
> >> And the Tucker circuit overcomes problems with the superhet.
>
> >I am not so sure it does.
>
> I trust the opinion of the man who built it more than the one who
> hasn't.
I suggest you BUILD a Tuckerdyne radio, before you place any trust in
anyone. Having a permantly skeptical attitude is part of the method
for developing ideas.
>
> >The superhet offered very good selectivity at the cost of audio
> >bandwidth, but you could make a superhet with wide AF BW. Makers just
> >didn't, because they'd successfully got people addicted to low AF BW
> >whichsuited bean counters.
>
> You need to decide whether your going to keep claiming it's wonderful
> or crap.
>
> >AFTER you've tried to make a synchrodyne successfully, then see what
> >you think.
>
> I already told you I have no interest in building one and neither do I
> intend to build an F-22 to see what it's like.
Then you'll end up more ignorant about matters raised in this
discussion than I am.
I found Tucker's idea was difficult to make work.
Superhets are easier to make work.
> >Sure, but communications radio techniques are all mainly utterly
> >unacceptable for Joe Punter, who wants excellent broadcast sound at
> >the flick of a switch, and different stations by turning one knob,
> >with no noises.
>
> Irrelevant.
Of course. YOU rabbit on with irrelvant BS then claim my comments are
irrelevant.
>
> > So all the fancy techniches used to comm radio are
> >irrelevant, because they focus on using small level signals to be able
> >to be recieved in a crowded band fulla noise.
>
> Nonsense.
Communications radio sets share many features with entertainment mass
media tube radios, but the comm sets use many techniques specific to
their use which are not wanted in the 6 tube set on the mantle piece
used for local station AM reception.
>
> >Indeed the mute was needed to block loud whistles when tuning.
>
> >Today we'd use touch tuning in 10kHz steps in US or 9kHz here. The
> >oscillator F is selected, not tuned with LC.
> >If one wanted to, one probably could use an SS step tuned oscilator
> >for use in a tubed superhet or synchrodyne. AM Stations here are all
> >expected to have accurate station frequencies at 9kHz along the AM
> >band and in fact there's no need for mechanical tuning. The type of
> >oscillator won't affect the sound quality.
>
> See? Try actually solving problems instead of perpetually bitching and
> you might get somewhere.
And just how many good ideas about PLL have you offered to the group
so far which can be implemented NOW, using tubes, and perhaps improved
upon?
> >> I'm sure they're interesting but without the articles they're not much
> >> else.
>
> >But these things were leading edge thoughts on radio design in their
> >day.
>
> Doesn't matter if they were reverse engineered from crashed space
> aliens at Area 51. Titles don't tell me anything other than someone
> wrote something.
That's it, be determined to stay ignorant. But the author list I
mention do have lots to say that s relevant.
>
> > You have not told me how your construction progress is proceeding
> >on anything better than in all those articles by greater minds than
> >yours.
>
> Yes I have. Precisely 0% seeing as how I still have no interest in
> building one, just like I've told you every time you babble that crap.
Ah, just an arm chair solderer & general bullshit artist. Go make
something or do something useful.
> Now, put a cleverly sized ...
Indeed, but I don't have time to R&D a better AM radio right now. Most
of my work with radios is re-engineering existing superhet AM radios
mainly wanted for strong local stations, so even considering changing
such things to use synchronous AM detection is never my aim, mainly
because I get excellent results with a very simple use of CF plus diode
+R+C AM detector.
It seems nobody has ever bothered to build a real PLL with tubes for
BC band radios. Its all become old hat in the world of chips. But I'm
into tubes, and to do better than Tucker did I'd have to work longer
and harder at it.
Patrick Turner.
John L Stewart
Quoted by Teflon John B
"Just because I'm not in the mood to build your toy for you."
>>>>>>>>>Don't depend on Teflon John B to build, provide schematics or
anything else for us.
Tefln John B likes others to do the sweat while he sits back &
comments.
But in the real world action talks & sheisse walks.
I would not want Teflon John B on my team. What a drag!!
Cheers to all, John S
--
John L Stewart
Patrick Turner
I've always found "Teflon John B" a tolerable, and even likable fellow
and I think he'd like us to know he's here for the intellectual
discussion and not to show off by his prolific efforts with a
soldering iron. He seems to have a respectable dislike for "ego
trips". Like myself and some others here, he struggles with ageing.
There are others here that "jarg the jargon" about electronics with or
without using tubes but whose lengthy posts don't really contribute
anything to making a better tube amp, and better AM radio, or a better
tubed anything, such as a more linear AM detector. Unfortunately, the
nursing home where Mr Huelett and Mr Packard reside at the ages of
112 and 113 does not have an internet facility, and of course the zeal
of these gentlemen now only extends to scrabble and chess. I heard
Peter Walker and Peter Baxandal have developed a mildly allergic
reaction to when anyone says the word "valve" or "transistor", and the
nurses in the UK establishments have to warn visitors about their
langauge, should they be granted an audience.
What seemed to start all this crap about PLL in AM radios was the idea
synchronous detection might work better than a diode + R + C detector.
People said there was never any need for a cathode follower to be used
to which I basically said "bollocks ! , of course there is a damn
need", and I recommend a pair of CF, not just one, to avoid the
dreadful cut off distortion at high % mod.
Anyway, I can think of two more ways to use a CF to drive a detector
circuit.
First is to have the usual CF, but its cathode is loaded with RF choke
to 0V. This RFC should be pie wound to avoid any C > 10pF and to
ensure CF and RFC do not act like a C+R detector. The CF triode may
need an RC circuit between cathode and RFC to give cathode biasing.
The IFT2 sec is at 0V potential, and direct couples to CF grid.
Then one has a Ge diode working from cathode into 22k resistance with
one end to 0V, and thus you get a waveform which is 1/2 the envelope
which is then directly applied to to the second grid of a CF. No
capacitors are used yet, and circuit Z is low enough to allow use of
Ge diodes or 6H6, 6AL5 etc.
The second CF cathode has 47k taken to -150Vdc rail, and the output
from cathode is taken to an LC filter with just enough R across the C
to critically damp the Fo of the LC, which should be at about 32kHz.
The XL and XC should be about 33k at 32kHz, ie, use 160mH plus 150pF,
with R damping of 47k. The choke should be pie wound to reduce self
capacitance. It could be a toroidal cored type with just the right
core permeability. Such a filter works like a choke input power supply
which detects the average peak voltage of the applied ac waveform.
Output is low, but free of most unwanted characteristics of most
"conventional" or "booooring" detectors to which Alex has referred.
Methinks the technical term for this detector is "infinite impedance
detector" becase the load on the IFT2 sec is indeed a virtual very
high Z of the CF. To get Q to where its wanted, R loading on the LC
between 100k and 220k should be used. Such R loading won't adversely
load the IF tube.
The second method is to use CF1 set up as above, but the RFC between
cathode and 0V is in fact a tapped autotransformer which raises the
455kHz IF waves to 3 times their level at cathode. The autotransformer
might also be tuned with a cap across the whole coil for 455kHz. This
increased IF voltage level is then applied to the diode and say a 47k
to 0V and thus the following levels of detected AF will be 3 times
higher. The CF need to be set up to cope with the dynamic range of
expected signals which should not be a problem in a set with AGC
voltages applied.
Because the detected waves are taken from a grounded winding it is
possible to use two diodes so that a positive going and negative going
output voltage is detected and thus TWO CF would be needed to buffer
the outputs from diode + R. Nice if one wants to drive a PP amp in the
radio.
Meanwhile, many retired bean counters in nursing homes have been
denied access to rec.audio.tubes.
The nurses decided that bean counters endured severe depression and
trauma after reading my posts which recommend nothing they can ever
agree with.
Meanwhile, Cadel Evans finally seems to have won the Tour De France
which goes to show that a short stature squeaky voiced humble pie
Ozzie could beat the pair tall good looking Schlek brothers from
Luxenburg. And Cadel is 8 years older than Andy Schlek, and didn't
have so much team support.
When you go for a ride today, watch you don't go to hard, and ride to
enjoy the afterglow of doing something, and not to spend 4 hours so
exhausted you can't do other sunday jollies.
It is forecast to be only 8C here today, maybe some rain, but I think
I'll do 70km, weather permitting - Too much yellow glow about to stay
indoors.
Patrick Turner.
John Byrns
Patrick Turner <in...@turneraudio.com.au> wrote:
> On Jul 23, 3:36 pm, flipper <flip...@fish.net> wrote:
> > On Fri, 22 Jul 2011 18:27:12 -0700 (PDT), Patrick Turner
> >
> > <i...@turneraudio.com.au> wrote:
> >
> > >>http://www.thevalvepage.com/radtech/synchro/section5/section5.htm
> >
> >
> > >> > and so just what sort of selectivity and
> > >> >freedom from monkey chatter and other effects one gets is not clear.
> > >> >The superhet overcomes most problems one has when trying to build a
> > >> >Tucker circuit.
Can you give a brief overview of the type of problems you encountered when you
tried to build a "Tucker circuit"?
> > >> And the Tucker circuit overcomes problems with the superhet.
> >
> > >I am not so sure it does.
> >
> > I trust the opinion of the man who built it more than the one who
> > hasn't.
>
> I suggest you BUILD a Tuckerdyne radio, before you place any trust in
> anyone. Having a permantly skeptical attitude is part of the method
> for developing ideas.
This comment suggests that you encountered substantial problems implementing the
"Tucker circuit"?
> > >The superhet offered very good selectivity at the cost of audio
> > >bandwidth, but you could make a superhet with wide AF BW. Makers just
> > >didn't, because they'd successfully got people addicted to low AF BW
> > >whichsuited bean counters.
> >
> > You need to decide whether your going to keep claiming it's wonderful
> > or crap.
> >
> > >AFTER you've tried to make a synchrodyne successfully, then see what
> > >you think.
> >
> > I already told you I have no interest in building one and neither do I
> > intend to build an F-22 to see what it's like.
>
> Then you'll end up more ignorant about matters raised in this
> discussion than I am.
>
> I found Tucker's idea was difficult to make work.
Did you try to build "tucker's circuit" from an existing schematic design, or
did you do your own design from the ground up? If you used an existing
schematic could you indicate which one it was?
I take it that what you built operated the detector at the actual frequency of
the broadcast station being received? Did your design have only a tuned
oscillator, or did it also include a tuned RF or antenna stage? What circuit
did you use for the synchronous detector itself?
This link to the "Tucker circuit" was given at the top of this post.
http://www.thevalvepage.com/radtech/synchro/section5/section5.htm
The "Tucker circuit" in Figure 8 looks virtually identical to the tube circuits
used to demodulate the L-R stereo sub carrier in the FM stereo system. The only
reason it should be anymore difficult to get operating than an FM stereo
decoder, and it is a big problem, is the fact that it is designed to be tuned
over the three to one frequency range of the MW broadcast band, rather than
operating at a single frequency, like a stereo decoder. That is why I earlier
suggested using the circuit as a detector in a superheterodyne, where it would
only have to operate at a single frequency, and wouldn't have to accommodate
variable tuning.
Reviewing this page I just discovered the "Curtis Homodyn Receiver" in figure 6
on the previous web page, here.
http://www.thevalvepage.com/radtech/synchro/section4/section4.htm
This circuit is essentially identical to what I proposed in an earlier post, and
might be easier to get working than the "Tucker circuit". The downside is that
the schematic is something of an artist's misconception, while the schematic of
the "tucker circuit" is more like a real schematic that you could directly build
from.
One thing I don't understand about the "Curtis Homodyn Receiver" is that in
addition to the Reactance tube that controls the VCO frequency in the PLL, there
is also a "Synchronization By Injection" circuit feeding the 4th grid of the
oscillator tube with some signal from the RF amplifier. At first glance this
seems redundant, however from my experience with "old" FM transmitters employing
PLLs, I know that these circuits don't always lock at turn on from a cold start
without some assistance from a startup circuit. Does anyone know if that is the
function served by the "Synchronization By Injection" circuit in the "Curtis
Homodyn Receiver"?
arthr...@webtv.net
> "Don Pearce" <s...@spam.com> wrote in message
NTSC NEVER looked good . It was the oldest color TV standard in the
world . Nobody will miss it .
arthr...@webtv.net
> negating any other alleged 'features'.- Hide quoted text -
>
> - Show quoted text -
How is that ? Even the motion picture standard was adopted as a mere
24 frames per second . Do you possess an unusual biological-optical
ability to see thing moving that fast ?
Patrick Turner
> > >NTSC NEVER looked good . It was the oldest color TV standard in the
> > >world . Nobody will miss it .
>
> > Neither did PAL or SECAM. The 50Hz flicker drove me near insane,
> > negating any other alleged 'features'.- Hide quoted text -
>
> > - Show quoted text -
>
> How is that ? Even the motion picture standard was adopted as a mere
> 24 frames per second . Do you possess an unusual biological-optical
> ability to see thing moving that fast ?- Hide quoted text -
>
> - Show quoted text -
Flipper evolved by means of a spurious genetic transmogrification
leading to him having the extra sensitive optical capabilities of a
fish, which needs to be able to see shark approaching with mouth wide
open, lest he be gobbled up.
Works two ways though. If I see Angelina Jollie coming at me with
mouth wide open I let her gobble me up, and I don't mind slower frame
speeds at all, to be sure now.
Patrick Turner.
arthr...@webtv.net
Amen .
John Byrns
flipper <fli...@fish.net> wrote:
> On Sat, 23 Jul 2011 21:32:25 -0500, John Byrns <byr...@sbcglobal.net>
> wrote:
>
> >This link to the "Tucker circuit" was given at the top of this post.
> >
> >http://www.thevalvepage.com/radtech/synchro/section5/section5.htm
> >
> >The "Tucker circuit" in Figure 8 looks virtually identical to the tube
> >circuits
> >used to demodulate the L-R stereo sub carrier in the FM stereo system. The
> >only
> >reason it should be anymore difficult to get operating than an FM stereo
> >decoder, and it is a big problem, is the fact that it is designed to be
> >tuned
> >over the three to one frequency range of the MW broadcast band, rather than
> >operating at a single frequency, like a stereo decoder. That is why I
> >earlier
> >suggested using the circuit as a detector in a superheterodyne, where it
> >would
> >only have to operate at a single frequency, and wouldn't have to accommodate
> >variable tuning.
>
> I still don't understand why you and Patrick see the 3:1 ratio as a
> PLL problem because the PLL doesn't have to pull and lock over that
> range, just whatever max station deviation from channel frequency is.
> You turn the tuning knob to get things 'in range'.
I missed the post where Patrick mentioned the 3:1 ratio as a problem? My only
point is that I can't see how having to deal with the 3:1 oscillator tuning
ratio, including tracking the Antenna and RF tuning sections, could possibly
make it easier to get this circuit working properly in your workshop in the back
garden shed. Operating the synchrodyne detector circuit at IF should simplify
getting it working properly, once one's confidence has been bolstered by
conquering this first step, then one could move on to the version operating
directly on frequency. My thought was simply to learning to crawl before trying
to learn to walk.
I would want my receiver to receive any station whose "primary service area", as
defined by the FCC in the US, I was located within. This probably would call
for a tuned antenna stage to minimize 3rd order IM. Also the RF amplifier
output should probably also be tuned to maximize signal to noise ratio,
especially for those stations where I am located on the fringe of the "primary
service area. This would call for a three gang tuning capacitor, or three
varactors.
> If the PLL pulled and locked over the entire MW band how the heck
> would you select a station?
I'm not sure I understand the question?! The oscillator has some means of being
manually tuned, a variable capacitor or other tuning device, stations are tuned
by setting the oscillator frequency to the frequency of the station it is
desired to receive, then the loop is made to lock on that frequency.
> An IF might be a good idea from the aspect of eliminating Lo feedback
> into the antenna and RF amp, though.
And of course as we would expect it also brings some new problems of its own.
> Actually, I've seen some 'synchronous detector' kits intended to be
> tacked onto an existing radio's 455 kHz IF.
I have three AM broadcast receivers here in the house that use a superheterodyne
circuit and a synchronous detector.
> >Reviewing this page I just discovered the "Curtis Homodyn Receiver" in
> >figure 6
> >on the previous web page, here.
> >
> >http://www.thevalvepage.com/radtech/synchro/section4/section4.htm
>
> I was just about to suggest Patrick read the whole Tucker article.
>
> The earlier Bellescize circuit 'looks' more like a PLL but I suspect
> it suffers from DC offset and phase modulation.
[Snip]
> You have to 'translate' their 'radio speak' into 'PLL speak'. Like,
> when Tucker explains "it is evidently necessary to prevent the natural
> frequency of the oscillator from drifting very far from the frequency
> to which it is made to synchronize" he's simply saying we need phase
> lock and 'the problem' is caused by injection lock being a first order
> PLL, with the attendant phase shift depending on how far the phase
> difference has to 'push' on the Lo to get it on frequency. And then
> there's AM phase distortion which I'm not sure either addressed.
What is the nature of the "AM phase distortion" you are speaking of? One of the
advantages of the synchronous detector over Patrick's "C+D" envelope detector is
that it is relatively immune to phase and amplitude distortion of the modulated
carrier being received.
John Byrns
flipper <fli...@fish.net> wrote:
> On Sun, 24 Jul 2011 12:03:43 -0500, John Byrns <byr...@sbcglobal.net>
> He claimed, first a varactor and then, a reactance tube couldn't
> handle the range.
Yes, I do remember those complaintsof Patrick's, I didn't associate them with
the problem of integrating the oscillator and antenna tuning though.
It isn't clear what kind of schematic he was trying to build from, I can see
that he may have had trouble getting a reactance tube working properly although
I would think it would be child's play to get a varactor working for the VCO/PLL
function.
Patrick has been unusually closed mouthed about what it was that he actually
tried building.
> > My only
> >point is that I can't see how having to deal with the 3:1 oscillator tuning
> >ratio, including tracking the Antenna and RF tuning sections, could possibly
> >make it easier to get this circuit working properly in your workshop in the
> >back
> >garden shed.
>
> I see. Well, I thought you were repeating Patrick's 'range' claim.
No, the range required of the reactance tube or varactor associated with the PLL
part of the circuit doesn't have to be very great, although the required range
would vary considerably over the tuning range, and have a considerable influence
on the gain and lock range of the PLL circuit over the band. Now if he was
talking about the "main" tuning capacitors for the antenna and oscillator
circuits, that would be a difference matter, special varactors are required to
cover the 3:1 frequency range, and the idea of using reactance tubes for that
function wouldn't have even entered my mind as a possibility.
> I was thinking homodyne might make that part easier since the tuning
> range and tanks could be identical but I was thinking a 'whole' radio.
I have been thinking about this as a detector for an otherwise working and fully
developed superheterdyne circuit. Until the past 24 hours it didn't even
seriously enter my mind to use these circuits as a complete radio as they are
shown in the old articles. Perhaps this bias comes from my familiarity with the
modern solid state AM stereo ICs which were used as a detector in a
superheterodyne following a conventional IF.
> > Operating the synchrodyne detector circuit at IF should simplify
> >getting it working properly, once one's confidence has been bolstered by
> >conquering this first step, then one could move on to the version operating
> >directly on frequency. My thought was simply to learning to crawl before
> >trying
> >to learn to walk.
>
> I certainly agree with the crawl first approach and tacking it onto an
> existing radio's IF might be easiest.
>
> >I would want my receiver to receive any station whose "primary service
> >area", as
> >defined by the FCC in the US, I was located within. This probably would
> >call
> >for a tuned antenna stage to minimize 3rd order IM. Also the RF amplifier
> >output should probably also be tuned to maximize signal to noise ratio,
> >especially for those stations where I am located on the fringe of the
> >"primary
> >service area. This would call for a three gang tuning capacitor, or three
> >varactors.
>
> Isn't that a bit past the crawl stage? I was thinking just the antenna
> tank and Lo tuning with 'refinements' later, if doing a 'whole' radio.
Probably, but you have to remember that prior to the past 24 hours I wasn't
thinking about a complete radio, only a detector, and those issues don't come up
directly when you are considering only a detector. They simply popped into my
mind as I was typing.
> >> If the PLL pulled and locked over the entire MW band how the heck
> >> would you select a station?
> >
> >I'm not sure I understand the question?!
>
> It was based on my thinking you were complaining about PLL tuning
> range like Patrick was.
>
> > The oscillator has some means of being
> >manually tuned, a variable capacitor or other tuning device, stations are
> >tuned
> >by setting the oscillator frequency to the frequency of the station it is
> >desired to receive, then the loop is made to lock on that frequency.
>
> Well, yes. That was my point about range. The PLL just has to pull and
> lock over the max deviation from station channel frequency.
So then I think we are in agreement here. Keep in mind though that the lock
range is going to vary from the bottom to the top of the band. The gain of the
PLL will change over the 3:1 frequency range, and it may even be desirable to
make the loop filter characteristics dependent on the tuned frequency, perhaps a
pot ganged to the tuning capacitor shaft.
> >> An IF might be a good idea from the aspect of eliminating Lo feedback
> >> into the antenna and RF amp, though.
> >
> >And of course as we would expect it also brings some new problems of its
> >own.
> >
> >> Actually, I've seen some 'synchronous detector' kits intended to be
> >> tacked onto an existing radio's 455 kHz IF.
> >
> >I have three AM broadcast receivers here in the house that use a
> >superheterodyne
> >circuit and a synchronous detector.
>
> Yeah. As mentioned above, I'm beginning to think that might be an
> easier place to start since an existing IF might be cleaner than going
> straight to the antenna from scratch.
Operating the detector directly on the received frequency does have a certain
seductive allure though, as it promises a simpler radio, the detector/PLL
circuit plus only an RF amplifier.
> >> >Reviewing this page I just discovered the "Curtis Homodyn Receiver" in
> >> >figure 6
> >> >on the previous web page, here.
> >> >
> >> >http://www.thevalvepage.com/radtech/synchro/section4/section4.htm
> >>
> >> I was just about to suggest Patrick read the whole Tucker article.
> >>
> >> The earlier Bellescize circuit 'looks' more like a PLL but I suspect
> >> it suffers from DC offset and phase modulation.
> >
> >[Snip]
> >
> >> You have to 'translate' their 'radio speak' into 'PLL speak'. Like,
> >> when Tucker explains "it is evidently necessary to prevent the natural
> >> frequency of the oscillator from drifting very far from the frequency
> >> to which it is made to synchronize" he's simply saying we need phase
> >> lock and 'the problem' is caused by injection lock being a first order
> >> PLL, with the attendant phase shift depending on how far the phase
> >> difference has to 'push' on the Lo to get it on frequency. And then
> >> there's AM phase distortion which I'm not sure either addressed.
> >
> >What is the nature of the "AM phase distortion" you are speaking of? One of
> >the
> >advantages of the synchronous detector over Patrick's "C+D" envelope
> >detector is
> >that it is relatively immune to phase and amplitude distortion of the
> >modulated
> >carrier being received.
>
> First recall that these circuits were based on injection lock with the
> second order PLL function tacked on (in the Curtis).
>
> Sorry if using "phase distortion" is poor terminology but I mean
> carrier-Lo phase shift and think of temporal changes, rather than a
> fixed offset, as 'distortion'. I.E. Carrier AM peaks are a 'bigger
> injection' than carrier troughs, and the carrier-Lo phase differential
> will change as a result. That's why I previously suggested an RF
> limiter.
OK, I got you, I thought you were speaking of phase distortion of the modulated
carrier by the radios RF circuits and during propagation through the either. If
I am correctly understanding you know, you are speaking of amplitude to phase
modulation effects occurring in the phase detector and possibly other parts of
the PLL circuit?
> Tack on a second order PLL and seems to me you have injection lock
> sticking in dynamic (AM) phase errors while the other is trying to
> remove it. Which one wins?
>
> Or maybe the second order PLL removes 'enough' of it and I'm worrying
> about nits.
Good question, I assume it would depend on the nature and order of the amplitude
to phase conversion.
> They were just beginning to recognize, and correct for, carrier-Lo
> phase differential and Adler had not yet explained the injection lock
> process so they may not have been aware carrier AM was another source
> of injection lock phase error.
Yes, as you say we have the benefit of hindsight, and the experience gained from
the millions of consumer AM broadcast radios that were build using this kind of
detector system.
John Byrns
Hi John,
Is the ³Teflon John B² you are referring to me, or is it just my ego that makes
me think that you are talking about me?
If ³Teflon John B² is not me, who is it?
Or are you saying that you believe ³Flipper² is one of my aliases?
If ³Teflon John B² is me, then I would suggest that you are slightly confused,
or maybe more than just slightly.
I did not make the original statement "Just because I'm not in the mood to build
your toy for you" that you quote. It was Flipper that made the original
comment, and I don't think I even repeated the quote as part of a reply to
Flipper's post.
There are two possible causes for your confusion. One, it may be an artifact of
³AudioBanter², the site you use as an interface to the Usenet, or two, it may be
something more serious which I will leave for you to contemplate privately.
Patrick Turner
> In article <John.L.Stewart.8707...@audiobanter.com>,
Just who did say "Just because I'm not in the mood to build your toy
for you." ??
It is a Flippereque statement as there is a style that is different to
"Teflon John".
But if Flipper said it, or John Byrns said it, probably it matters
not, because both John Byrns and Flipper are loathe to build anything
at any time and both wanna just sit around all day chatting while
doing nothing. OK for them.
I have work to do. Soldering up tube circuits that work well.
Patrick Turner.
John Byrns
flipper <fli...@fish.net> wrote:
> On Sun, 24 Jul 2011 17:36:31 -0500, John Byrns <byr...@sbcglobal.net>
> wrote:
>
> >In article <tsko27hinp8r8t5su...@4ax.com>,
> > flipper <fli...@fish.net> wrote:
> >
> >> On Sun, 24 Jul 2011 12:03:43 -0500, John Byrns <byr...@sbcglobal.net>
> >> wrote:
> >>
> >> >In article <ao1n27lesdrlsue1d...@4ax.com>,
> >> > flipper <fli...@fish.net> wrote:
> >> >
> >> >> I still don't understand why you and Patrick see the 3:1 ratio as a
> >> >> PLL problem because the PLL doesn't have to pull and lock over that
> >> >> range, just whatever max station deviation from channel frequency is.
> >> >> You turn the tuning knob to get things 'in range'.
> >> >
> >> >I missed the post where Patrick mentioned the 3:1 ratio as a problem?
> >>
> >> He claimed, first a varactor and then, a reactance tube couldn't
> >> handle the range.
> >
> >Yes, I do remember those complaintsof Patrick's, I didn't associate them
> >with
> >the problem of integrating the oscillator and antenna tuning though.
>
> Well, not being able to tune the range at all sort is sort of
> 'integral' to everything ;)
>
> >It isn't clear what kind of schematic he was trying to build from, I can see
> >that he may have had trouble getting a reactance tube working properly
> >although
> >I would think it would be child's play to get a varactor working for the
> >VCO/PLL
> >function.
>
> I don't think he was working from anything. Just in a "won't work"
> mood.
>
> >Patrick has been unusually closed mouthed about what it was that he actually
> >tried building.
[Snip]
> I think the reason for the plethora of approaches is there isn't
> really a 'project'.
>
> I got involved when Patrick said he couldn't find any 'tube' PLLs and
> I was just explaining that he wouldn't find them described as such
> because the term didn't exist until later, and then provided some
> examples.
>
> Trying to explain they existed sort of drove the conversation in all
> manner of directions, like Patrick trying to 'coerce' me into building
> a 'Tucker'.
They may even have existed in the tube days, in exactly the form Patrick is
looking for, during the first run at AM stereo in the US in the late 1950s.
There were half a dozen or so systems proposed by various companies, most of
which used FM or PM to convey the stereo difference signal, but there may have
been a QAM proposal among them that would have included the tube PLL circuit
Patrick is looking for. I have descriptions of all the systems buried in my
library, but due to extreme domestic entropy, which is this summers project to
make a dent in, I don't have the data to hand to verify if one of the systems
was a QAM system with a PLL that Patrick could use.
Since Patrick has been loath to rise to the bait I have dangled and give us an
overview of what sort of Synchrodyne he has attempted to solder together, with
unsatisfactory results, I decided to root through the archives to see what he
said on the subject in the past.
I found the following quotes in the rec.audio.tubes archives, except for the
first which was part of a personal email I received from Patrick. I hope he
will forgive my lapse of Netiquette in quoting it here in this public group.
From a private email:
Date: Sat, 18 Aug 2001 11:35:27 +1000
"I guess true synchronous detection could be used for the 38 Khz signal, just
like a Synchrodyne reciever. The one I have in mind was By D.G. Tucker from
1947, but it never caught on, as it really did not offer any better overall
performance, and this method of direct detection did not catch on until chips
came along. There was a Synchrodyne circuit for AM which came out in Electronics
Australia in 1962, and it used a 6BE6 as the self oscillating mixer with the
oscillations locked to the incoming carrier, and a simple R for a load, and a C
to remove RF ripple."
From the usenet group rec.audio.tubes:
Date: Thu, 17 Jan 2002 15:32:00 +1100
"Less is more sometimes with radio,and two detectors in series seem unecessary."
"I tried building a Synchrodyne reciever, with tubes, and it quite stumped me,
for a variety of reasons, so I returned to the idea of a decent superhet, and
have not looked back. D.G.Tucker brought out a tubed pure Synchrodyne in 1947,
and I started with a similar idea to his, and found it difficult to stop it
oscillating where I didn't want it too."
Date: Sat, 12 Jun 2004 01:02:30 +1000
"My paper files have around 20 different circuits for AM tuners including a
fairly simple synchrodyne ( or direct conversion ) two tube sets which use a
6EJ7 for an RF amp, and followed by a 6BE6 synchronous detector."
"I tried building one, but audio output was low, stability was difficult, and
and a superhet proved far better."
"Then there were several if not many synchrodyne and some homodyne designs in
Wireless World over the years, but these were all chip based, except the early
D.G.Tucker circuit of 1947."
Date: Wed, 23 Jun 2004 02:10:33 +1000
"I did play around with the Tucker tubed synchrodyne but gave up when I
concluded that my superhet idea was easier to build."
Date: Fri, 12 Nov 2010 02:11:07 -0800 (PST)
"I guess a PLL oscillator which would "run on" during short time absences of a
synchronized and limited carrier would be better. The last time I tried was
1999 when I spent a week trying t get a tubed "Synchrodyne" first designed by a
Mr Tucker in 1947, and published by Wireless World that year. It never was a
commercial success and could not compete with good superhet performence, at
least for broadcast AM bands. Besides, stations today routinely use right up to
100% modulation."
"Anyway, my synchrodyne was very hard to get working anywhere near as well as a
good superhet even when I resorted to using a much simpller circuit with 6EJ7
input RF gain amp and a 6BE6 self oscillating AM detector; plus there's the
howls and whistles when tuning and the the monkey chatter from other stations."
Date: Mon, 11 Jul 2011 03:13:34 -0700 (PDT)
Subject: Re: VLF stability in Williamson-type amplifiers
"I tried to build a version of the DG Tucker Synchrodyne circuit published in
Wireless World in about 1947. Maybe its now online some place, and what
prevented progess was the making of a suitable balanced synchronous demodulator.
Probably the best way is to use a toroidal transformer with the core ? just
right for range of RF frequencies. But I never had time to explore how to make
such a tranny. The tucker circuit uses lots more tubes than a superhet and needs
much more practical expertise to get running without loud whistles while tuning.
It was a potentially excellent thing but it was never to become popular because
the superhet was king. Then tried making a synchrodyne based on a self
oscillating 6BE6, and there are some simple circuits of those around, just RF
input tube and 6BE6 needed only. That sort of worked a bit but monkey chatter
and whistles and controlling oscillations just right were easier said than done
so I abandoned the idea and proceeded with a good superheat."
That brings us to the current thread which Patrick started on 18 Jul 2011 under
the subject "Phase Locked Loop with vacuum tubes." I later changed the subject
to "Some thoughts on PLLs, Synchrodynes, and AM modulation depth", and with this
post am changing again to " Turner's Synchrodyne"
The above quotes make it fairly clear that what Patrick built was a project
described in a 1962 issue of "Electronics Australia". Patrick says this design
used two tubes in a direct conversion circuit, with a 6EJ7 as an RF amplifier
stage, and a 6BE6 as a combined oscillator and synchronous detector. Presumably
the oscillator section of the 6BE6 was "injection locked".
I suspect that an easier to get working beginner's circuit, requiring no special
parts, could be created by adding only one tube to the Electronics Australia
project. First in keeping with my notion of crawling before walking, I would
change the design from a direct conversion receiver to a superheterodyne
receiver with a synchronous detector. I would replace the 6EJ7 RF stage with a
second 6BE6 operating as a converter from the broadcast frequency to a 455 kHz
IF. The synchronous detector and oscillator would remain essentially the same
as in the "Electronics Australia" design using a 6BE6.
The big change to the circuit would be the means of synchronizing the oscillator
portion of the synchronous detector. Instead of injection locking the
oscillator in the second 6BE6, a PLL would be used. A third tube, a 6AU6 would
be added, with its grid feed from the same IF signal feeding the 6BE6
synchronous detector. A slightly modified 455 kHz discriminator transformer, an
easily available part, is used along with two GE diodes as a phase detector with
the 6AU6 feeding one input and the 455 kHz oscillator section of the second 6BE6
feeding the phase detector's second input. The output of the phase detector,
through a loop filter, would then control a varactor diode connected in the 455
kHz oscillator circuit, "phase locking" it to the IF signal.
Achieving the initial "phase lock" with this simple circuit would probably make
tuning in a station rather finicky. Some additional circuitry to facilitate the
initial lock would eliminate this problem, at the cost of some added complexity.
This might be as simple as a tune/listen switch to change the bandwidth of the
loop filter.
A slight variation of this circuit would be to fix the frequency of the 455 kHz
oscillator, and connect the varactor into the superheterodyne oscillator
circuit. Each variation has pluses and minuses.
Once one has gained some confidence with this beginner's IF Synchrodyne, a
direct conversion variant, replacing the 6BE6 converter with a 6EJ7 RF amplifier
as in the original "Electronics Australia" design, but retaining the PLL
concept, could be tried with its added problems. One problem with this PLL
direct conversion approach is that there isn't an obvious off the shelf phase
detector transformer available.
Patrick Turner
snip
> Trying to explain they existed sort of drove the conversation in all
> manner of directions, like Patrick trying to 'coerce' me into building
> a 'Tucker'.
** I strongly recommended you try my cathode follower detector, and I
don't coerce anyone into building anything. Of course when I do
recommend something, usually it is a very simple easy thing which
might occupy a wet sunday arvo which I forsee might be a pleasure
besides being educational. I've never coerced anyone into using more
than one tube at a time. A whole synchrodyne radio is several tubes at
least, and probably 3 month's worth of sundays to begin to overcome
numerous design problems.
Its no use me even cordially inviting anyone to build anything because
the mindset of everyone here is so stultifyingly moribund. Cold
soldering irons are normal, and people dare to never walk outside
their front gate to explore anything any more.
They may even have existed in the tube days, in exactly the form
Patrick is
looking for, during the first run at AM stereo in the US in the late
1950s.
** Er, just what did you ever really think I was looking for? Your
powers of imagination have run away like an over excited dog off the
lead in a nice big parkland.
There were half a dozen or so systems proposed by various companies,
most of
which used FM or PM to convey the stereo difference signal, but there
may have
been a QAM proposal among them that would have included the tube PLL
circuit
Patrick is looking for.
** So where are the full schematics with explanations and waveforms?
** Here in Oz, stereo AM just never ever took off. Stereo FM sure did,
followed by surround sound. But with AM, nobody used much more than an
SE output tube for 3 watts, one channel only, until the 1970's, when
Japanese junk imports began to trickle and then flood into Oz after
trade tarrifs were reduced because there were more australians willing
to vote for cheaper prices than there were voters who'd vote to
preserve their mate's jobs.
I have descriptions of all the systems buried in my
library, but due to extreme domestic entropy, which is this summers
project to
make a dent in, I don't have the data to hand to verify if one of the
systems
was a QAM system with a PLL that Patrick could use.
** It sounds like you must be about 94 John, and doing just about
anything takes +20dB longer than it did when you were 30, and getting
it right might take +20dB more capability. My mother of 94 was an
excellent pianist and secretary at 26 before she ruined her
development by bending to the urge towards motherhood, after which all
her talents fell by the wayside in favour of becoming an excellent
cook and house keeper. I now understand her incapacity, and her
extreme limited ability to do anything much at all. I will be like her
one day if I live that long. SO, I have to wonder where people are
here, where they are at, and I smell no fumes from soldering iron just
like I smell no wondrous aromas from my mother's kitchen when she used
to cook.
Since Patrick has been loath to rise to the bait I have dangled and
give us an
overview of what sort of Synchrodyne he has attempted to solder
together, with
unsatisfactory results, I decided to root through the archives to see
what he
said on the subject in the past.
** What bait had you ever dangled John?
** I simply stated I tried Tucker's idea but was stumped on the
transformers for the balanced mixer with 4 diodes.
The R&D would have taken too long, and nobody I contacted knew
anything about anything much, including a bunch of local radio
amateurs, most of whom are dead now.
I found the following quotes in the rec.audio.tubes archives, except
for the
first which was part of a personal email I received from Patrick. I
hope he
will forgive my lapse of Netiquette in quoting it here in this public
group.
** I doubt anyone would need to apologise for re-broadcasting my
private emails. Wikileaks couldn't offend me. I have nothing evil to
hide.
From a private email:
Date: Sat, 18 Aug 2001 11:35:27 +1000
"I guess true synchronous detection could be used for the 38 Khz
signal, just
like a Synchrodyne reciever. The one I have in mind was By D.G. Tucker
from
1947, but it never caught on, as it really did not offer any better
overall
performance, and this method of direct detection did not catch on
until chips
came along. There was a Synchrodyne circuit for AM which came out in
Electronics
Australia in 1962, and it used a 6BE6 as the self oscillating mixer
with the
oscillations locked to the incoming carrier, and a simple R for a
load, and a C
to remove RF ripple."
** The 2 tube circuit was by Ian Pogson, published in Radio TV &
Hobbies.
It had a 6EH7 tuned RF amp and self oscilating 6BE6 into which was fed
the tuned RF signal.
AF came out of the anode circuit. So very very simple, except it
wasn't as good a superhet.
From the usenet group rec.audio.tubes:
Date: Thu, 17 Jan 2002 15:32:00 +1100
"Less is more sometimes with radio,and two detectors in series seem
unecessary."
"I tried building a Synchrodyne reciever, with tubes, and it quite
stumped me,
for a variety of reasons, so I returned to the idea of a decent
superhet, and
have not looked back. D.G.Tucker brought out a tubed pure Synchrodyne
in 1947,
and I started with a similar idea to his, and found it difficult to
stop it
oscillating where I didn't want it too."
**Indeed. Since that time, I've developed the CF detector in various
forms to render further investigation of synchronous tube radios to be
pointless. I can get excellent AF BW, low noise, excellent skirt
selectivity, freedom from whistles or monkey chatter from a superhet.
Perhaps someone at somewhere might prove they can build a better AM
radio with tubes or chips but NOBODY has even come close to proving it
with a practical example. I apologise in advance for my arrogance, but
it must be remembered by all that I have been repairing or rebuilding
several AM radios each year at least for the last 15 years and NOT ONE
set in its original condition sounds as well as the radio in my
kitchen which I designed & cobbled together in 1999. I'll eat that
radio when someone fronts up with a better sounding radio.
Date: Sat, 12 Jun 2004 01:02:30 +1000
"My paper files have around 20 different circuits for AM tuners
including a
fairly simple synchrodyne ( or direct conversion ) two tube sets which
use a
6EJ7 for an RF amp, and followed by a 6BE6 synchronous detector."
"I tried building one, but audio output was low, stability was
difficult, and
and a superhet proved far better."
** Indeed. Your point in quoting me?????
** yeah yeah, .... So???
** I think you have let intellectual licence run away with the
imagination dog in the park.
** What exact arrangement of tubes and coils etc could ever be worthy
to be named after me?
The above quotes make it fairly clear that what Patrick built was a
project
described in a 1962 issue of "Electronics Australia".
** I tried to build both Tucker's Synchrodyne published in WW, and
Pogson's Synchrodyne published in R,TV&H which became Electronics
Australia.
Patrick says this design
used two tubes in a direct conversion circuit, with a 6EJ7 as an RF
amplifier
stage, and a 6BE6 as a combined oscillator and synchronous detector.
Presumably
the oscillator section of the 6BE6 was "injection locked".
** With both RF input and oscillator operating at the same F and with
same L and C tank values, and applied into the same single 6BE6
frequency converter tube, the oscillations tended to lock easily while
modulation % was low.
I suspect that an easier to get working beginner's circuit, requiring
no special
parts, could be created by adding only one tube to the Electronics
Australia
project. First in keeping with my notion of crawling before walking,
I would
change the design from a direct conversion receiver to a
superheterodyne
receiver with a synchronous detector. I would replace the 6EJ7 RF
stage with a
second 6BE6 operating as a converter from the broadcast frequency to a
455 kHz
IF. The synchronous detector and oscillator would remain essentially
the same
as in the "Electronics Australia" design using a 6BE6.
** You can sit back in your arm chair and type up your suspicions all
day long John but it cuts no ice with me. I'll only start to be more
receptive to recomendations AFTER YOU have done the donkey work of
making up the chassis and building the coils and ensuring its stable
and getting it all to work IN YOUR TIME and NOT MINE.
** Its a tough love approach John. But after the superhet began to
become king by about 1933, it has managed to stay king for the last 78
years *if one thinks in terms of using tubes and IFTs* Many other ways
to receive normal broadcast AM or short wave have been devised and
I've not heard anything better than a good tubed superhet. Remarkable
multiband sets were made with SS devices but all concentrated on low
AF bandwidth, and none offered hi-fi sound. About the most elaborate
tubed set I worked on was a 26 tube Racal radio which offered
astounding communications abilities. But for good local BC band
reception all the fancy techniques in a Racal or any other damned
complex bit of gear are just not needed.
** Synchronous detection along with other techniques became possible
and even popular when silicon chips allowed fast enough wave forms
with predictable outcomes with perhaps hundreds of bjts within chips.
some of the in-chip techniques could be repllcated with tubes, but
you'd need box fulls of them, and it just isn't on, right, and nobody
has ever bothered. Even to make a Gilbert Cell with tubes takes 4 x
6DJ8, and lord knows what sort of troubles you'd have to get it to
works as well as a chip with Gilbert Cell within.
** As tubes faded away from being mainstream in the radio receiver
building industry, nobody was able to make any further improvements
which would be lauded by industry leaders who became totally devoted
herd members in persuit of solid state solutions to every single
problem preferably with ICs, because they were CHEAPER than using room
fulls of girls all soldering bjts into PCBs. Now all circuits are
never touched by interfering human hands and are designed by a
computer, and wave soldered together. The AM broadcasts I now hear
from the sets which now cost $00.20 cents each to include on a PCB are
basically attrocious, except on my old tube set.
** I come along in about 2000, some 40 years after everyone in the
radio industry now wonderes what the heck tubes are or were, and tell
ppl that a double CF type of AM detector works better than all the
other crap that was industry standard in 1960. I am then hounded down
and shot at from all directions.
** Well, all the buckshot missed.
The big change to the circuit would be the means of synchronizing the
oscillator
portion of the synchronous detector. Instead of injection locking
the
oscillator in the second 6BE6, a PLL would be used. A third tube, a
6AU6 would
be added, with its grid feed from the same IF signal feeding the 6BE6
synchronous detector. A slightly modified 455 kHz discriminator
transformer, an
easily available part, is used along with two GE diodes as a phase
detector with
the 6AU6 feeding one input and the 455 kHz oscillator section of the
second 6BE6
feeding the phase detector's second input.
There is NO easily available 455kHz discriminator transformer. One
must DESIGN and MAKE the unit.
The output of the phase detector,
through a loop filter, would then control a varactor diode connected
in the 455
kHz oscillator circuit, "phase locking" it to the IF signal.
** Someone at Somewhere is very welcome to build such a circuit in
THEIR TIME.
Achieving the initial "phase lock" with this simple circuit would
probably make
tuning in a station rather finicky. Some additional circuitry to
facilitate the
initial lock would eliminate this problem, at the cost of some added
complexity.
This might be as simple as a tune/listen switch to change the
bandwidth of the
loop filter.
** Define "finicky". I suggest it is NOT an engineering term, but I
might assume that when tuning, lock might occur when you were say
20kHz off the local station, then lock would "hang on" until you were
20kHz away, so whistles while tuning would not be heard. In simple
sets made to recieve morse code without modulation, a BFO is used to
tune 1 kHz away from the IF frequency, so you hear the morse.
Similarly, the BFO is used to put a carrier into a SSB signal thus
making SSB comprehensible. But in synchronous, no such beating of
close RF signals is permissible, and oscillator needs to be locked to
RF or IF signal F.
** But the details of how you get rid of "finicketty-ness" and make
the circuit easily usable by an average dumb punter take some
effort.
A slight variation of this circuit would be to fix the frequency of
the 455 kHz
oscillator, and connect the varactor into the superheterodyne
oscillator
circuit. Each variation has pluses and minuses.
** One could easily build a crystal controlled 455kHz oscillator.
Crystals are available.
Once one has gained some confidence with this beginner's IF
Synchrodyne, a
direct conversion variant, replacing the 6BE6 converter with a 6EJ7 RF
amplifier
as in the original "Electronics Australia" design, but retaining the
PLL
concept, could be tried with its added problems. One problem with
this PLL
direct conversion approach is that there isn't an obvious off the
shelf phase
detector transformer available.
** I await you detailed schematic telling us all how-to-do-it but no
doubt the date for the release of such schematic info from the John
Byrns Establishment is years away, pending the overcoming of a
multitude of problems not mentioned right now, but which certainly
exist, or will soon, during the process.
Patrick Turner.
--
Regards,
John Byrns
John Byrns
Patrick Turner <in...@turneraudio.com.au> wrote:
snip
Hi Patrick,
I was having trouble understanding why you started this thread, originally
titled "Phase Locked Loop with vacuum tubes", especially considering that you
have complained over the years about your inability to build a properly working
"Tucker Sybchrodyne", and your eventual discovery that a superheterodyne using
your "C+D" detector circuit provided unexcelled performance, especially
considering its high bean counter appeal.
After reviewing this thread, and some of the related currently running AM
detector threads, I now see that you seem to want to build a PLL type AM
detector for use in a superheterodyne receiver. Why you want to do this is not
at all clear since you already have the "C+D" detector which you say is the
ultimate.
Flipper has already a link to one schematic for a tube based PLL operating at
3.58 MHz. In one of the AM detector threads I pointed out two or three other
tube PLL applications for you, although unlike Flipper I didn't provide any
links. The schematic for one of the tube based PLLs I mentioned, operating at
about 5 MHz, is also available on the web, complete with explanations and
waveforms. Either of these PLLs could be adapted for operation at 455 kHz by
changing the frequency determining components.
Unfortunately you seem to be a lazy guy, unwilling to sharpen your pencil and
get out your slide rule, to modify one of the available tube PLL circuits for
use as part of an AM detector.
Now you are demanding that we do your work for you and provide łfull schematics
with explanations and waveforms˛ that you can use to build your tube PLL AM
detector. I suggest that you take your own advice and continue using your łC+D˛
detector, at least until next year when you retire on your old age pension.
That will eliminate your need to spend so much time repairing old radio and
Hi-Fi equipment to earn money, with your time thus freed up you will have time
to further develop the old tube PLL circuits into a form suitable for use as an
AM detector.
Patrick Turner
> In article <5b50b6e4-1448-4373-8439-38f6eb7d0...@h7g2000prf.googlegroups.com>,
> Patrick Turner <i...@turneraudio.com.au> wrote:
>
> snip
>
> Hi Patrick,
>
> I was having trouble understanding why you started this thread, originally
> titled "Phase Locked Loop with vacuum tubes", especially considering that you
> have complained over the years about your inability to build a properly working
> "Tucker Sybchrodyne", and your eventual discovery that a superheterodyne using
> your "C+D" detector circuit provided unexcelled performance, especially
> considering its high bean counter appeal.
I cannot see what stopped you being able to understand the FACT that
virtually no PLL circuits using tubes have ever been built, as
equivalents of what may be done using chips, and for application in AM
radios.
Sure I gave up trying to build a synchrodyne, but it doesn't mean I
was unable to, had I been more persistant. There was limited time
then, as there is now for the R&D needed to make a decent balanced AM
de-modulator one way or another, using tubes.
>
> After reviewing this thread, and some of the related currently running AM
> detector threads, I now see that you seem to want to build a PLL type AM
> detector for use in a superheterodyne receiver. Why you want to do this is not
> at all clear since you already have the "C+D" detector which you say is the
> ultimate.
Tucker's original circuit appeals because of the reputed benefits of
direct conversion receivers. Thousands of radio hams with direct
conversion receivers can't be all wrong, although I expect hi-fi
sound, when they don't.
My double CF detector does work better than most if not all other ways
to extract AF from AM using just 2 triodes and no more other parts
than used in conventional AM detectors.
The bean counters of 1950 could never have approved the use of my two
added triodes ( 1 x 12AU7 tube) so don't talk to me about my ideas
having bean counter appeal. About none of my ideas suit bean counters,
ie, anyone seeking to remove function quality to favour shareholder
returns, or to make out they are a hero of the revolution..
>
> Flipper has already a link to one schematic for a tube based PLL operating at
> 3.58 MHz.
Sure some examples exist but nothing devoted to the BC band.
> In one of the AM detector threads I pointed out two or three other
> tube PLL applications for you, although unlike Flipper I didn't provide any
> links. The schematic for one of the tube based PLLs I mentioned, operating at
> about 5 MHz, is also available on the web, complete with explanations and
> waveforms. Either of these PLLs could be adapted for operation at 455 kHz by
> changing the frequency determining components.
I'll leave you to provide the info, and produce the addapted schematic
and get it running as a prototype and post your results.
Meanwhile what I read here is just old men's hot air about what might
be, might not be, and I can only really relate to REALITY.
>
> Unfortunately you seem to be a lazy guy, unwilling to sharpen your pencil and
> get out your slide rule, to modify one of the available tube PLL circuits for
> use as part of an AM detector.
Call me lazy if you like, but where are your efforts on the subject?
So before anyone calls me lazy, they have to show thay are doing more
than I am to produce working gear.
I'm employed on client projects and although I think always about
better ways of doing things I don't have unlimited time to implement
them. Even if I did manage to get a synchronous AM radio or homodyne
radio to perform better than what I know now, there would be virtually
no justification whatsoever to incorporate into anyone's existing
radio set, as I would be having to build so much new stuff and remove
stuff that is more easily improved.
> Now you are demanding that we do your work for you and provide full schematics
> with explanations and waveforms that you can use to build your tube PLL AM
> detector.
I'll always demand of other what I demand of myself. If people here
expect intellectual respect, or respect of their constructional
cabilities, then they need to get off their arses to their work sheds
and get busy. We could all sit around ALL DAY but I can't afford it.
Too many people want me to fix their junk, and I need de munny.
> I suggest that you take your own advice and continue using your C+D
> detector, at least until next year when you retire on your old age pension.
> That will eliminate your need to spend so much time repairing old radio and
> Hi-Fi equipment to earn money, with your time thus freed up you will have time
> to further develop the old tube PLL circuits into a form suitable for use as an
> AM detector.
If I had to try to build a direct conversion again, i'd probably use a
3 gang tuning cap. Two would be for a an RF input amp to allow use of
a ferrite rod antenna, and a following tank after a pentode gain tube.
Tucker's set dosn't have this feature, but has a two pentode cascaded
untuned amp with NFB to raise RF input levels at the output of what is
a low impedance output amp. I'd prefer a tunable RF front end and a
simble CF at its OP will reduce the Zout which is best to drive a
balanced modulator circuit. That could be similar to Tuckers and
possibly give real hi-fi, but the reality can only be found by doing,
not spending hours bullshitting here about it.
I already have a working FM generator which works to produce 455kHz AM
with +/- 40kHz each side for examining IFT selectivity curve shapes.
Its F is controlled by a tuning gang plus use of about 11 paralleled
68V x 5W zener diodes which won't conduct like ordinary veractor
diodes when used in tube circuits which produce quite high oscillator
output voltages in tank circuits where one wants to use such purpose
built varicap diodes. I did try, but ordinary varicaps were useless.
Anyway, zeners make fine varicaps.
Now the synchrodyne set needs a VFO so the third of 3 tuning gangs is
used to tune it. But its actual C on the LC tank might be controlled
by DC working on zeners to change C. But I have to work out details of
how to apply the Vdc to cause locking, so a limiter is needed, so a
6AU6 powered off the recovered and amplified RF is needed. Tube count
is mounting up.
Anyway, I have ideas about how to do a synchrodyne and I have all the
hardware, but I shall never say it will work better than what I can
now already do with a suprerhet. Sure I could probably just build a
synchrodyne module which worked off an existing 455khz IF strip -
maybe easier because there is far less F variation to have to worry
about and no worry about tracking by RF input stages and VFO tunable
oscillators.
Its obvious to me neither you or flipper can ever be relied upon to
provide the world with alternative working circuits for DIYers which
work better than existing.
Stay seated and never raise a sweat if you must, but while nothing
seems to happen at your place, I have to do things, and because I like
doing them.
Someon'e's knocking at my door again.
Patrick Turner.
John Byrns
Patrick Turner <in...@turneraudio.com.au> wrote:
> On Jul 27, 11:02�am, John Byrns <byr...@sbcglobal.net> wrote:
> > In article
> > <5b50b6e4-1448-4373-8439-38f6eb7d0...@h7g2000prf.googlegroups.com>,
> > �Patrick Turner <i...@turneraudio.com.au> wrote:
> >
> > snip
> >
> > Hi Patrick,
> >
> > I was having trouble understanding why you started this thread, originally
> > titled "Phase Locked Loop with vacuum tubes", especially considering that
> > you
> > have complained over the years about your inability to build a properly
> > working
> > "Tucker Sybchrodyne", and your eventual discovery that a superheterodyne
> > using
> > your "C+D" detector circuit provided unexcelled performance, especially
> > considering its high bean counter appeal.
>
> I cannot see what stopped you being able to understand the FACT that
> virtually no PLL circuits using tubes have ever been built, as
> equivalents of what may be done using chips, and for application in AM
> radios.
Because chips came after tube PLLs, why would anyone want to duplicate chip
circuitry with tubes, they are different technologies and the circuits that suit
them best differ. I am not sure why you obsess over building Gilbert cells with
tubes?
Relative to schematics, I forgot to mention that quite a few late 1930s high end
AM radios with motorized tuning included an AFC system similar to what was used
in tube FM tuners. These circuits included a 455 kHz discriminator and
reactance tube circuit to control the local oscillator. With a slight change to
the wiring of the discriminator transformer, to feed the centertap of the
secondary from the local oscillator rather than from the transformer primary,
presto you have the schematic of a complete PLL circuit that will lock the
oscillator to the IF frequency. Of course the oscillator must also be modified
to operate at 455 kHz.
John Byrns
flipper <fli...@fish.net> wrote:
> On Tue, 26 Jul 2011 20:02:45 -0500, John Byrns <byr...@sbcglobal.net>
> wrote:
>
> >In article
> ><5b50b6e4-1448-4373...@h7g2000prf.googlegroups.com>,
> > Patrick Turner <in...@turneraudio.com.au> wrote:
> >
> >snip
> >
> >Hi Patrick,
> >
> >I was having trouble understanding why you started this thread, originally
> >titled "Phase Locked Loop with vacuum tubes", especially considering that
> >you
> >have complained over the years about your inability to build a properly
> >working
> >"Tucker Sybchrodyne", and your eventual discovery that a superheterodyne
> >using
> >your "C+D" detector circuit provided unexcelled performance, especially
> >considering its high bean counter appeal.
> >
> >After reviewing this thread, and some of the related currently running AM
> >detector threads, I now see that you seem to want to build a PLL type AM
> >detector for use in a superheterodyne receiver. Why you want to do this is
> >not
> >at all clear since you already have the "C+D" detector which you say is the
> >ultimate.
>
> I think you misinterpreted the 'purpose' of that post.
>
> Near as I can tell the genesis of this jumble began way back in the
> "VLF stability in Williamson-type amplifiers" thread because Pogosso
> mentioned using his shelf in AM radios. That diverged into various sub
> threads among which detectors came up.
Yes, I think the first follow on thread was Pogosso's "AM detector, part 1".
> Somewhere in the jumble Patrick apparently decided his CF detector was
> being criticized and went into Last Starfighter Death Blossom mode
> shooting anything that even smacked of 'AM detector'.
I must plead guilty that I have criticized Patrick's "C+D" detector to the
extent that I question the need for the first cathode follower.
> I don't know who first mentioned 'PLL' but his post as a "
It was Pogosso in his "AM detector, part 1" thread that first mentioned "PLL" in
connection with a solid state PLL detector module he fits to old radios.
Patrick was right on it the next day with a request for schematics of vacuum
tube phase locked loops.
I still don't understand Patrick's interest in vacuum tube PLL circuits given
that he already has his "C+D" detector, and PLL detector circuits up the tube
count considerably.
John Byrns
flipper <fli...@fish.net> wrote:
> On Tue, 26 Jul 2011 23:18:49 -0500, John Byrns <byr...@sbcglobal.net>
> Oh. Well, I knew there was something somewhere but I couldn't recall.
>
> Now that you mention it I went back and it appears the beginning was
> Pearce mentioning a synchronous detector. Then, in a follow up, you
> suggested a PLL for over 100% modulation and Alex agreed. Alex also
> mentioned his SS detector module.
>
> I see it now. You mentioned PLLs in TV sets, Patrick said he didn't
> work on TV sets and hadn't ever seen any tube PLLs but was going to do
> a google. The post in question was the result.
Sounds about right.
> That is where I came in because I had seen your post, his, and the
> 'google result' so I was simply trying to explain they wouldn't be
> called "phase locked loops" because that term didn't not come into
> being until later.
So when did the term or TLA "PLL" come into use. I'm trying to remember what
the PLL in old Television sets was called, I'm thinking it might have been
called the Horizontal AFC circuit.
> >I still don't understand Patrick's interest in vacuum tube PLL circuits
> >given
> >that he already has his "C+D" detector, and PLL detector circuits up the
> >tube
> >count considerably.
>
> Sorry but I'm sure you noticed by now I accidentally hit some 'magic'
> key that sent the message before it was done.
>
> What I had meant to finally explain is his post was a he 'looked',
> there ain't none, and he was going back to something useful instead of
> chasing fairy circuits.
Well he sort of changed the goal posts at some point, first he asked for vacuum
tube PLL circuits that could be used for better AM reception, later he changed
it to demand schematics of complete PLL based AM detectors, no engineering
required.
Patrick Turner
> >Hi Patrick,
> >I was having trouble understanding why you started this thread, originally
> >titled "Phase Locked Loop with vacuum tubes", especially considering that you
> >have complained over the years about your inability to build a properly working
> >"Tucker Sybchrodyne", and your eventual discovery that a superheterodyne using
> >your "C+D" detector circuit provided unexcelled performance, especially
> >considering its high bean counter appeal.
>
> >After reviewing this thread, and some of the related currently running AM
> >detector threads, I now see that you seem to want to build a PLL type AM
> >detector for use in a superheterodyne receiver. Why you want to do this is not
> >at all clear since you already have the "C+D" detector which you say is the
> >ultimate.
Flipper then says.....
> I think you misinterpreted the 'purpose' of that post.
>
> Near as I can tell the genesis of this jumble began way back in the
> "VLF stability in Williamson-type amplifiers" thread because Pogosso
> mentioned using his shelf in AM radios. That diverged into various sub
> threads among which detectors came up.
You are approximately correct. Pogooooso who invented the word
booooring ro describe old radio AM detectors did indeed suggest I use
an extra C in a FB loop to supposedly counter problems which I
mentioned were basically non existant in anything I built, and most of
everything else.
>
> Somewhere in the jumble Patrick apparently decided his CF detector was
> being criticized and went into Last Starfighter Death Blossom mode
> shooting anything that even smacked of 'AM detector'.
JB didn't see the need for the extra use of CF triodes in a an AM
detector. I tried to describe the benefits, suggesting he try my idea
before condemning it, but of course that was never to happen when
there's an egotistical opportunity to keep dismissing a good idea,
rather than to move even 1 centimetre towards a soldering iron and
CRO.
>
> I don't know who first mentioned 'PLL' but his post as a "
>
> <snip>- Hide quoted text -
>
> - Show quoted text -
And you can see what a mess Goggle does with NG delivery to me.
- no quoted text able to be seen.
Anyway, I tried to look at the schematic of the PLL mentioned on page
461 within the .pdf for the 37 tube colour TV at the site at
http://antiqueradio.org/sitemap.htm
But the pdf was largely un-readable, having been scanned by an
incompetent. And so I found far too much time would be needed to de-
cypher the schematic to see just what flipper was talking about. I
ain't no fukkin expert on tubed color TV sets from 1950s, and I'll
stay that way with very scant information, and posted so you can't
read what you're lookin at.
I guess flipper or JB will NEVER provide a copied version of the tubed
PLL schematic with full ammended details to allow it to be used in a
synchrodyne radio. Its WAAAAAAAAAAAAAAAAY beyond their willingness to
give, while they remain extremely willing to shoot everyone else down
who challenges them in in any way.
Since posting to JB in my last post I had a good look again at my
455kHz FM generator. It uses 5 x 68V x 5W zener diodes in parallel as
varicap diodes to alter C across the LC tank in a cathode follower
type of triode oscillator using 1/2 a 12AU7. While in FM mode, the RF
gene does not use a tuning gang, although some fine tuning of the
centre F is possible with a pot which slightly alters Vdc on ZDs.
The 5 ZDs have grounded anodes, and the 5 cathodes connect via 2N6 to
the grid end of the oscillator coil.
This "top" end of the coil is cap coupled to triode grid, while triode
cathode is taken to a tap about 25% up from earthy end of coil which
is at 0V. The Vo output from the coil goes via 3k9 to the grid of CF
buffer stage, so that anything connected to VFO output can't change
the tuned F.
The voltage range applied to the ZD cathodes may be varied by a pot
from +24Vdc to + 40Vdc. The applied Vac to "wobbulate" or FM modulate
the 455kHz is about within this range from a saw tooth generator I
have built in, but any old AC signal will do to produce FM to trace
the selectivity curves for a 455kHz radio IF strip.
A switch allows a change of ZDs to just 1, not 5, thus allowing a
930kHz signal to be FM'd, and applied and detected by the AM set.
Now a phase detector **could be** be fairly easily be built using a
suitable 1:1 RF transformer with secondary having a CT, and two
diodes, plus some R&C bits, all very much like an FM radio ratio
detector which is arranged to produce a Vdc output which is applicable
to a reactance triode, 1/2 12AT7, which then controls the FM set RF
oscillator F at over 100MHz.
The VDC generated by the phase detector goes +ve for where VFO F goes
higher than carrier, -ve if VFO F goes lower, and we might *HOPE* that
the Vdc change is enough to lock a VFO and that the time constant is
long enough with Vdc LPF network that VFO will run on without
significant F change if the carrier signal drops to nothing during
100% modulation.
The only reason I see for use of PLL techniques for a synchrodyne are
to get over the problem of intermittent locking of a locked oscillator
even with a limiter stage present.
But Tucker's radio has its VFO tunable for all of the BC band. This
requires a large change in C between say 400pF and 30pF. Let us assume
we might find that a limiter stage using a pentode would help to give
a better signal to use to lock the VFO, and if you have a tuned VFO
with a tuning gang and you have a parallel tuning diode, then getting
the C change needed by a Vdc applied might be difficult to get working
right, so perhaps all the tuning might be done using a pot and varied
DC and nothing but veractors.
I cannot list all forseable bothers trying to do all this.
But if it can be done for where VFO must make F between 530kHz and
1,710kHz, then its better to do it than retain the superhet mixer
stage, which we might want to chuck out BECAUSE we wish to use a
synchrodyne instead, and gain selectivity offered by the audio LPF
rather than by the IFT selectivity.
So if people want to know how I might get better hi-fi from a tubed
synchrodyne set which I would want to work better than Tucker's 1947
job, then they might see agreement about using a following summary of
stages :-
TRF input stage, ferrite rod antenna input coil, AVC applied to grid
of V1 pentode.
One tuning gang, 30pF-400pF.
RFT at anode, secondary tuned with second tuning gang, 30pF-400pF.
V2 CF buffer stage.
Q of LC should not be too high to caused side band cutting and RF BW
should be at least 8kHz at the low end of band.
V2 buffer drives balanced modulator using Tucker's circuit with
transformers using details to be worked out.
V2 buffer also drives V3 pentode limiter to make near constant
amplitude output signal.
V4 CF buffer used after V3 to drive phase detector to produce Vdc to
change veractor C of oscillator.
LPF for dc path keeps Vdc constant for limiter signal drop outs when
AM % goes to 100%.
V5 triode CF oscillator with tunable tank using the 3rd available
tuning gang.
V6 triode oscillator output buffer used to drive VFO input to balanced
demodulator.
Veractor used in parallel with tuning gang.
Application of Vdc from phase detector to ensure VFO stays locked to
limiter carrier F.
Tuning of oscillator should track RF stage tuning
The AF from balanced de-mod stage buffered by V7, and active second
order RC + V8 CF LPF filter used before V9, V10 audio output stages.
It obviously might be easier to use a PLL and oscillator which worked
at 455kHz only, to avoid having to tune the oscillator over a wide
range.
Then the RF input stage might be simplified.
There are probably 101 other ways which might be utilised, but the
synchrodyne will probably end up more complex than the standard 2 tube
superhet AM tuner used in most AM radios for strong local stations.
I do not know if the synchrodyne balanced demodulator can produce a
Vdc which may be used for VFO F control in addition to producing audio
output.
But one thing is for sure, to make a synchrodyne with tubes to meet
modern use expectations is a real big ask.
Patrick Turner.
John Byrns
Patrick Turner <in...@turneraudio.com.au> wrote:
> Anyway, I tried to look at the schematic of the PLL mentioned on page
> 461 within the .pdf for the 37 tube colour TV at the site at
> http://antiqueradio.org/sitemap.htm
> But the pdf was largely un-readable, having been scanned by an
> incompetent. And so I found far too much time would be needed to de-
> cypher the schematic to see just what flipper was talking about. I
> ain't no fukkin expert on tubed color TV sets from 1950s, and I'll
> stay that way with very scant information, and posted so you can't
> read what you're lookin at.
>
> I guess flipper or JB will NEVER provide a copied version of the tubed
> PLL schematic with full ammended details to allow it to be used in a
> synchrodyne radio. Its WAAAAAAAAAAAAAAAAY beyond their willingness to
> give, while they remain extremely willing to shoot everyone else down
> who challenges them in in any way.
How am I trying to shoot your PLL efforts down? I'm trying to encourage you to
experiment with a PLL based radio, and your latest post gives me hope that
perhaps you are giving the matter some serious consideration. I am trying to
give you a leg up by filling in a few details that you seem to be unaware of,
you are free to use, or not use, this information in any way you are comfortable
with.
[Snip]
> Now a phase detector **could be** be fairly easily be built using a
> suitable 1:1 RF transformer with secondary having a CT, and two
> diodes, plus some R&C bits, all very much like an FM radio ratio
> detector which is arranged to produce a Vdc output which is applicable
> to a reactance triode, 1/2 12AT7, which then controls the FM set RF
> oscillator F at over 100MHz.
>
> The VDC generated by the phase detector goes +ve for where VFO F goes
> higher than carrier, -ve if VFO F goes lower, and we might *HOPE* that
> the Vdc change is enough to lock a VFO and that the time constant is
> long enough with Vdc LPF network that VFO will run on without
> significant F change if the carrier signal drops to nothing during
> 100% modulation.
The �LPF� is called the �Loop Filter�, the design of this filter is something
you should read up on. I'm not a �PLL� expert but I think you want a double
time constant filter here, this typically involves two resistors and two
capacitors. This consists of a short time constant filter to remove the carrier
frequency components and other grunge from the output of the phase detector.
This is followed by a long time constant which serves as a modified integrator
to allow the VCO to track through the periods of carrier lock. The long time
constant part of the filter is modified so that while it integrates the phase
error signal over the long term, it allows some higher frequency components to
pass through to provide faster locking and better loop stability, remember this
is a negative feedback loop so there may be stability issues. Hopefully there
is a fully fledged PLL expert reading this who can better explain this.
> The only reason I see for use of PLL techniques for a synchrodyne are
> to get over the problem of intermittent locking of a locked oscillator
> even with a limiter stage present.
That sounds about right, we need a second order loop to ride us through the
periods of carrier loss, or even effective phase reversal as may happen with
heavy modulation during selective fading.
> But Tucker's radio has its VFO tunable for all of the BC band. This
> requires a large change in C between say 400pF and 30pF. Let us assume
> we might find that a limiter stage using a pentode would help to give
> a better signal to use to lock the VFO, and if you have a tuned VFO
> with a tuning gang and you have a parallel tuning diode, then getting
> the C change needed by a Vdc applied might be difficult to get working
> right, so perhaps all the tuning might be done using a pot and varied
> DC and nothing but veractors.
Yes, there are certainly problems here, it's not immediately obvious how to
connect a varactor to the oscillator section of a standard multi gang tuning
condenser while providing both the needed capacity change at the low end of the
band, and also not unduly increasing the minimum capacity at the high end of the
band, that is required to provide the 9:1 capacity change needed to tune the
entire MW band.
This 9:1 impedance change across the band will also affect the gain of the PLL
circuit, influencing its performance including lock range and stability.
It's not clear to me how much substituting varactors for a mechanical tuning
gang simplifies the problem, it presumably would if we were willing to use
opamps and piecewise linear summing circuits in the DC circuits controlling the
varactors. Maybe there is a simple solution that I am just not seeing.
In any event there is something very satisfying about a mechanical tuning gang
in a tube radio.
> I cannot list all forseable bothers trying to do all this.
Yes, while the direct conversion, or �Zero-IF�, approach has a strongly
seductive allure, its realization does raise a multitude of bothers. I'm not
sure how common direct conversion radios are outside of the �Ham� radio
community, does anyone know? I suspect that most of the so called �Zero-IF�
receivers are actually superhetrodynes, where what at one time would have been
double conversion superheterodynes have had their second IFs replaced with a
�Zero-IF� and detector.
All these bothers are why I like my crawl before walking superhetrodyne with PLL
synchronous detector approach, at least for a first project.
> But if it can be done for where VFO must make F between 530kHz and
> 1,710kHz, then its better to do it than retain the superhet mixer
> stage, which we might want to chuck out BECAUSE we wish to use a
> synchrodyne instead, and gain selectivity offered by the audio LPF
> rather than by the IFT selectivity.
Yes, the direct conversion approach is very seductive, no question. With the
superheterodyne approach, if you make the IF very wide, perhaps using a 2 MHz
IF, then you can control the audio bandwidth with the audio LPF just as with the
direct conversion approach.
That's a very good start!
Using a two tube superhetrodyne as a base line is bean counter thinking. We
want the best possible High Fidelity reception under as many conditions as
possible, this is only possible using a true synchronous detector, pretenders
need not apply
> I do not know if the synchrodyne balanced demodulator can produce a
> Vdc which may be used for VFO F control in addition to producing audio
> output.
No, you need separate detectors for the �PLL� and to recover the audio. The two
detectors must be provided with carrier signals from the oscillator 90 degrees
out of phase with each other. Maintaining the required 90 degree phase shift
over a 3:1 frequency range is another big potential gotcha for a tube based
direct conversion receiver. In a solid state design this problem would be
simply dealt with by operating the oscillator at 4 or 8 times the received
frequency, and using digital dividers to generate the 90 degree phasing between
the two local oscillator signals. A large number of tubes would probably be
required to do it this way in a tube based circuit.
You may also want to add a lock detector circuit, and an envelope detector to
your list above. The lock detector could switch the parameters of the �Loop
Filter� when out of lock to facilitate locking, and also switch to an envelope
detector during tuning.
> But one thing is for sure, to make a synchrodyne with tubes to meet
> modern use expectations is a real big ask.
Yes, it's a very big ask!
John Byrns
flipper <fli...@fish.net> wrote:
> On Wed, 27 Jul 2011 13:08:40 -0500, John Byrns <byr...@sbcglobal.net>
> wrote:
>
> >In article
> ><bedea09a-b22c-409d...@q29g2000prj.googlegroups.com>,
> > Patrick Turner <in...@turneraudio.com.au> wrote:
>
> <snip>
>
> >> I do not know if the synchrodyne balanced demodulator can produce a
> >> Vdc which may be used for VFO F control in addition to producing audio
> >> output.
> >
> >No, you need separate detectors for the �PLL� and to recover the audio. The
> >two
> >detectors must be provided with carrier signals from the oscillator 90
> >degrees
> >out of phase with each other. Maintaining the required 90 degree phase
> >shift
> >over a 3:1 frequency range is another big potential gotcha for a tube based
> >direct conversion receiver. In a solid state design this problem would be
> >simply dealt with by operating the oscillator at 4 or 8 times the received
> >frequency, and using digital dividers to generate the 90 degree phasing
> >between
> >the two local oscillator signals. A large number of tubes would probably be
> >required to do it this way in a tube based circuit.
>
> Pardon me if this is "not a radio guy" dumb idea but that is one
> reason I was thinking about the 6ME8 because you can get at it single
> ended.
>
> Looking at the bottom of page 9 here...
>
> http://jlandrigan.com/files/Receivers/SSB%20Exciter%20Circuits%20Using%20the%2
> 07360.pdf
>
> The 6ME8 has different gain and biasing but it's functionally the same
> thing so I'm pondering that product detector as a sort of starting
> point.
>
> Add a reactance tube to make a VCO of the LO.
I'm Following you to this point, beyond here I'm either not following you, or
it's a "not a radio guy" dumb idea, or most likely a little bit of both. I'm
also not familiar with the application of this tube, although I have at least
heard of it.
> Now, seems to me you might could get the control signal from a PP
> transformer on the 6ME8 outputs into a single secondary. (You'd also
> need to at least R isolate the single ended outputs rather than just
> RF ground them). Filtered, of course.
You mention getting the control signal from the secondary of a PP transformer, I
don't see how that could work as the control signal is DC? In any case what are
the "single ended outputs" and the Rs to isolate them all about?
> I think you're still 90 degrees but that just means a lower single
> ended amplitude, doesn't it? Which I'm thinking is a lesser problem
> than the other.
If it is at 90 degrees, which is what the PLL would be driving towards, the
output would be zip. Say it isn't quite 90, the problem is that the phase angle
changes the amplitude of the recovered modulation, but the uncorrelated noise on
the received signal remains constant, so the SNR of the recovered audio goes to
pot when the phase angle differs from zero.
> Obviously just an 'idea' and not a design.
Unfortunately I'm not "a radio guy" either, I just played one while I was in
college and for a year after I graduated, so what I say could easily be total BS.
John L Stewart
Did anyone mention IBOC in North America? That will pretty well ZAP any
improved AM detector & many ordinary ones as well. Listen in for IBUZ!
Cheers, John
--
John L Stewart
John Byrns
flipper <fli...@fish.net> wrote:
> On Wed, 27 Jul 2011 20:35:32 -0500, John Byrns <byr...@sbcglobal.net>
> Sorry, I was way too brief about my "not a radio guy" dumb idea.
And my reading comprehension was compromised last night, I failed to notice your
statement �Looking at the bottom of page 9 here...�, and even though I read
through the entire paper, I ended up looking at the schematic on page 2.
> >> Now, seems to me you might could get the control signal from a PP
> >> transformer on the 6ME8 outputs into a single secondary. (You'd also
> >> need to at least R isolate the single ended outputs rather than just
> >> RF ground them). Filtered, of course.
> >
> >You mention getting the control signal from the secondary of a PP
> >transformer, I
> >don't see how that could work as the control signal is DC? In any case what
> >are
> >the "single ended outputs" and the Rs to isolate them all about?
>
> First, there's two take offs in my crazy idea with one being 'like'
> (but not exactly) the shown single ended audio and then the 'added on'
> PP transformer. The added on transformer passes IF and is post
> filtered to DC.
Can you explain how the IF would be �post filtered to DC�?
> I'm thinking each half of the primary in series with the plates, like
> your typical PP amp output stage, which means the plate signals can't
> be AC bypassed to ground in the single ended audio take off or else
> the transformer feed is screwed. Might could put a second transformer
> in there for the audio but I was thinking simple R isolation, between
> the plates and filter, might be sufficient. I'd duplicate it on both
> sides, even though one is 'unused' for audio, to keep plate balance.
>
>
> >> I think you're still 90 degrees but that just means a lower single
> >> ended amplitude, doesn't it? Which I'm thinking is a lesser problem
> >> than the other.
> >
> >If it is at 90 degrees, which is what the PLL would be driving towards, the
> >output would be zip. Say it isn't quite 90, the problem is that the phase
> >angle
> >changes the amplitude of the recovered modulation, but the uncorrelated
> >noise on
> >the received signal remains constant, so the SNR of the recovered audio goes
> >to
> >pot when the phase angle differs from zero.
>
> I think the question is output of what? There's 2 in my wacky idea: a
> PP transformer with the other being a single ended audio take off.
Output of the demodulated audio.
> At 90 degrees the PP transformer's single secondary should average
> (filtered) to 0, which is right for 0 phase error. Phase error to
> either side should produce a DC (after filtered) error in that
> polarity to drive the VCO.
I still don't understand how the DC is produced, through a transformer?
> At 90 degrees we have equal but opposite audio and carrier on each
> plate (which is why it nulls in the PP tranny) but the audio takeoff
> is single ended, which isn't 'null'. I'm guessing it's half, 6 dB
> down, from what you'd have in the 'ideal case' (assuming all else was
> equal) of creating a quadrature Lo signal into a second mixer but it's
> a heck of a lot simpler and maybe 6 dB isn't too horrible a sacrifice.
The wanted audio, although not the uncorrelated noise, is attenuated to zero at
90 degrees, not just 6 dB, even from a single ended output. Remember we aren't
talking SSB here, where the phase of the reinserted carrier doesn't affect the
amplitude of the demodulated audio, we are talking DSB where carrier phase is
critical.
> An alternate might be to use a dual primary, dual secondary,
> transformer for the audio and flip the phase on one secondary so it
> adds.
That's fine for the audio, but it still doesn't explain how the control signal
is derived.
> Did I manage to sensibly convey the idea?
Yes, except for the part about how the DC control signal gets through the
transformer. Even ignoring that, I don't think the idea will work because it
violates what we learned in High School Trigonometry class. I don't believe
that the system can be made to work without using two separate �modulators� or
�phase detectors�, one operating at 90 degrees to provide the control signal and
a second operating in phase to recover the audio.
John Byrns
> Did anyone mention IBOC in North America? That will pretty well ZAP any
> improved AM detector & many ordinary ones as well. Listen in for IBUZ!
I don't think anyone mentioned that, however the OP who asked the question is
located in OZ, do they use �IBOC� in OZ?
The wording of your comment suggests that IBOC may not �ZAP� some �ordinary� AM
detectors, was it your intention to imply that, or was it just an artifact of
your writing style? If it was intentional could you reveal which �ordinary� AM
detectors are not ZAPPED by IBOC.
Maybe you, or someone else on the group, can enlighten us about the nature of
the IBOC signal and how it affects various types of detectors? I get the
impression that there are both in-phase and quadrature IBOC subcarriers in the
areas greater than 5 kHz above and below the main carrier which must be removed
by filtering. I originally had the impression that the IBOC subcarriers within
5 kHz of the main carrier were in quadrature with it, or otherwise arranged so
that they would have minimal impact of the SNR of the demodulated audio below 5
kHz. Is this true, I seem to remember reading something more recently that said
it wasn't true? If it is true that the subcarriers within 5 kHz are in
quadrature, a true synchronous detector would reject the ZAPPING better than an
envelope detector. Also if a post detection filter is used to eliminate the
noise above 5 kHz, a synchronous detector would also be more effective. If very
narrow IF filtering is used to eliminate the subcarriers more than 5 kHz from
the main carrier, then the detector probably has little effect, although we are
left with typical AM radio frequency response beginning to cutoff at 2 kHz,
rather than getting a full 5 kHz audio response.
I would be surprised if a true synchronous detector doesn't resist ZAPPING by
IBOC better than an �ordinary� detector.
Does any one know the details of the IBOC signal, and how the subcarriers are
constructed?
John Byrns
flipper <fli...@fish.net> wrote:
> On Thu, 28 Jul 2011 08:28:06 -0500, John Byrns <byr...@sbcglobal.net>
> wrote:
>
> >In article <ckg137947aecoskfq...@4ax.com>,
> > flipper <fli...@fish.net> wrote:
> >
> >> Sorry, I was way too brief about my "not a radio guy" dumb idea.
> >
> >And my reading comprehension was compromised last night, I failed to notice
> >your
> >statement �Looking at the bottom of page 9 here...�, and even though I read
> >through the entire paper, I ended up looking at the schematic on page 2.
>
> Is that maybe still confusing the AM demod issue?
???
> I've tried doing some simulations substituting NPNs because I don't
> have a sheet beam tube model but I'm so pissed at this POS
> Circuitmaker.
>
> >> >> Now, seems to me you might could get the control signal from a PP
> >> >> transformer on the 6ME8 outputs into a single secondary. (You'd also
> >> >> need to at least R isolate the single ended outputs rather than just
> >> >> RF ground them). Filtered, of course.
> >> >
> >> >You mention getting the control signal from the secondary of a PP
> >> >transformer, I
> >> >don't see how that could work as the control signal is DC? In any case
> >> >what
> >> >are
> >> >the "single ended outputs" and the Rs to isolate them all about?
> >>
> >> First, there's two take offs in my crazy idea with one being 'like'
> >> (but not exactly) the shown single ended audio and then the 'added on'
> >> PP transformer. The added on transformer passes IF and is post
> >> filtered to DC.
> >
> >Can you explain how the IF would be �post filtered to DC�?
>
> It might need to be rectified but basically you have 455kHz phase
> pulses coming out. When 90 degrees they will be equal and opposite,
> for a net of 0. On either side of 90 they aren't equal so you can
> derive a DC offset from that.
As far as I know there are only three signals at each anode:
1. A DC signal, riding on the B+ present at the anode, that is proportional to
the carrier level multiplied by the cosine of the phase angle between the
received carrier and the locally generated carrier. Relative to the B+ on the
anode this DC component reaches a maximum when the phase offset between the
received and locally generated carriers is zero degrees, becomes zero when the
phase offset is 90 or 270 degrees, and becomes a maximum in the negative
direction at 180 degrees phase offset.
This DC signal can be used to control a VCO in a "PLL" by using a differencing
circuit to subtract the DC voltage at one anode from the other thereby canceling
the B+ voltage, this differencing works because the desired DC voltages on the
two anodes move in opposite directions since the IF phase driving the second
anode is 180 degrees out of phase with that driving the first anode. As a
control voltage for a VCO in a "PLL" the VCO phase would be driven towards 90
degrees where the DC difference signal is zero, positive on one side and
negative on the other.
2: The recovered modulation, a.k.a. the audio, voice music or whatever. The
amplitude of the recovered modulation varies with the same cosine function of
the phase offset as the DC component does. The recovered audio is maximum at
zero degrees phase offset, inverted at 180 degrees phase offset, and is nulled,
or becomes zero, at a 90, or 270 degree phase offset. This is in direct
conflict with the action of the DC control voltage which drives the loop close
to a 90 degree phase offset. At this point the modulation recovery is minimal,
and to make matters worse the quadrature noise component of the received signal
is maximized, seriously degrading the Signal to Noise Ratio.
3. A component at twice the carrier, or IF, frequency. I would have to get out
my High School Trigonometry book to be sure, but I think the amplitude of this
2Fc signal is constant, independent of the phase offset between the received
carrier and the local carrier, with only the phase angle changing as the phase
offset changes.
If a transformer is used in the anode circuits of the tube, only the recovered
modulation and the 2Fc signal would make it through to the transformer
secondary. The audio signal doesn't seem like it would be particularly useful
as a control signal for our "PLL", especially considering that it may not always
be present, as in quiet spots in a program, although granted quiet spots are
frowned upon in modern radio broadcasting.
The 2Fc signal could be compared with a 2Fc reference, say 910 kHz in the IF
case, and used to lock the loop. I believe this loop would lock at either of
two phase angles, which would result in a potential ambiguity in the phase of
the recovered audio, which may not be important, except that the phase could
flip from time to time. Also, without getting out my High School Trigonometry
book, which by now it should be obvious I am trying to avoid, it is not obvious
to me what the phase offset at 455 kHz would be, at lock. If it is not the
desired zero or 180 degrees, a simple phase shift network in the 910 kHz circuit
should fix the problem. The 455 kHz signal is of course derived from the 910
kHz oscillator circuit by a divider circuit, or more likely the 910 kHz signal
would be derived from the 455 kHz oscillator by using a frequency doubler
circuit.
Why would we want to go to all this extra trouble, we still need two balanced
modulators? It doesn't save us anything, indeed we have added an additional
circuit, the frequency doubler, and all we have gained is a 180 degree phase
ambiguity.
Did you have a different "post filtering" technique in mind?
> >> I'm thinking each half of the primary in series with the plates, like
> >> your typical PP amp output stage, which means the plate signals can't
> >> be AC bypassed to ground in the single ended audio take off or else
> >> the transformer feed is screwed. Might could put a second transformer
> >> in there for the audio but I was thinking simple R isolation, between
> >> the plates and filter, might be sufficient. I'd duplicate it on both
> >> sides, even though one is 'unused' for audio, to keep plate balance.
> >>
> >>
> >> >> I think you're still 90 degrees but that just means a lower single
> >> >> ended amplitude, doesn't it? Which I'm thinking is a lesser problem
> >> >> than the other.
> >> >
> >> >If it is at 90 degrees, which is what the PLL would be driving towards,
> >> >the
> >> >output would be zip. Say it isn't quite 90, the problem is that the
> >> >phase
> >> >angle
> >> >changes the amplitude of the recovered modulation, but the uncorrelated
> >> >noise on
> >> >the received signal remains constant, so the SNR of the recovered audio
> >> >goes
> >> >to
> >> >pot when the phase angle differs from zero.
> >>
> >> I think the question is output of what? There's 2 in my wacky idea: a
> >> PP transformer with the other being a single ended audio take off.
> >
> >Output of the demodulated audio.
>
> Are you on the right schematic now?
I'm on page 9, is that the right one?
> >> At 90 degrees the PP transformer's single secondary should average
> >> (filtered) to 0, which is right for 0 phase error. Phase error to
> >> either side should produce a DC (after filtered) error in that
> >> polarity to drive the VCO.
> >
> >I still don't understand how the DC is produced, through a transformer?
>
> See above.
That doesn't help without a more detailed description of the "post filtering"
that you are proposing.
> >> At 90 degrees we have equal but opposite audio and carrier on each
> >> plate (which is why it nulls in the PP tranny) but the audio takeoff
> >> is single ended, which isn't 'null'. I'm guessing it's half, 6 dB
> >> down, from what you'd have in the 'ideal case' (assuming all else was
> >> equal) of creating a quadrature Lo signal into a second mixer but it's
> >> a heck of a lot simpler and maybe 6 dB isn't too horrible a sacrifice.
> >
> >The wanted audio, although not the uncorrelated noise, is attenuated to zero
> >at
> >90 degrees, not just 6 dB, even from a single ended output. Remember we
> >aren't
> >talking SSB here, where the phase of the reinserted carrier doesn't affect
> >the
> >amplitude of the demodulated audio, we are talking DSB where carrier phase
> >is
> >critical.
>
> We aren't inserting a carrier.
That's just a matter of semantics, what I was referring to was the local carrier
used to demodulate the signal by whatever means. This could actually be a large
amplitude carrier signal added to the IF signal, or reinserted, and feed to a
simple diode detector.
> Anyway, when I ran simulations I did get single ended audio with 90
> degrees Lo-carrier, or at least close. I can't say much else about it
> because Circuitmaker keeps going loco and I'm not getting consistent
> results so something is 'wrong'. Maybe I was getting a rectification
> effect.
Hmm, makes one wonder how quadrature modulation systems, AM stereo, digital
Television over cable, and others, manage(d) to work?
> I'm also not convinced my circuit is representative of the sheet beam
> tube.
I don't think the details of the sheet beam model matter to this discussion, as
long as it sort of acts like a multiplier.
Speaking of "sheet beam" tubes, isn't this essentially the tube version of the
Gilbert Cell that Patrick is looking for?
> So, maybe it's a great idea with the minor inconvenience of not
> working ;)
That's possible, although not yet proven.
> >> An alternate might be to use a dual primary, dual secondary,
> >> transformer for the audio and flip the phase on one secondary so it
> >> adds.
> >
> >That's fine for the audio, but it still doesn't explain how the control
> >signal
> >is derived.
> >
> >> Did I manage to sensibly convey the idea?
> >
> >Yes, except for the part about how the DC control signal gets through the
> >transformer.
>
> I didn't say put DC 'though' the transformer. You have 2 phased 455kHz
> signals going into it and I said DC came from post filtering.
Yes, but I am waiting for an explanation of how the post filtering works?
> After looking at it again I think you'd need to rectify to get a
> second order filter.
Or more specifically feed it through another phase detector of some sort with a
2Fc reference.
> > Even ignoring that, I don't think the idea will work because it
> >violates what we learned in High School Trigonometry class. I don't believe
> >that the system can be made to work without using two separate �modulators�
> >or
> >�phase detectors�, one operating at 90 degrees to provide the control signal
> >and
> >a second operating in phase to recover the audio.
>
> I dunno. My high school trig class didn't talk much about single ended
> sheet beam tubes.
Of course not, neither did mine, just trigonometric equations and related
theory. AM DSB modulation is an example of such an equation.
Patrick Turner
> In article <bedea09a-b22c-409d-9a12-4e0e8fd8c...@q29g2000prj.googlegroups.com>,
> Patrick Turner <i...@turneraudio.com.au> wrote:
>
> > Anyway, I tried to look at the schematic of the PLL mentioned on page
> > 461 within the .pdf for the 37 tube colour TV at the site at
> >http://antiqueradio.org/sitemap.htm
> > But the pdf was largely un-readable, having been scanned by an
> > incompetent. And so I found far too much time would be needed to de-
> > cypher the schematic to see just what flipper was talking about. I
> > ain't no fukkin expert on tubed color TV sets from 1950s, and I'll
> > stay that way with very scant information, and posted so you can't
> > read what you're lookin at.
>
> > I guess flipper or JB will NEVER provide a copied version of the tubed
> > PLL schematic with full ammended details to allow it to be used in a
> > synchrodyne radio. Its WAAAAAAAAAAAAAAAAY beyond their willingness to
> > give, while they remain extremely willing to shoot everyone else down
> > who challenges them in in any way.
>
> How am I trying to shoot your PLL efforts down? I'm trying to encourage you to
> experiment with a PLL based radio, and your latest post gives me hope that
> perhaps you are giving the matter some serious consideration. I am trying to
> give you a leg up by filling in a few details that you seem to be unaware of,
> you are free to use, or not use, this information in any way you are comfortable
> with.
Just exactly what details are you giving anyone here on the group?
Where is the schematic, preliminary test results?
I have not noticed any experts here. None. Zip. Zero. Lotsa wannabes.
Lotsa people suggesting I go build something, while they sit back and
watch.
I'm too busy re-engineering people's gear to re-invent a wheel with
many more wooden spokes than the wheel I already about.
>
> > The only reason I see for use of PLL techniques for a synchrodyne are
> > to get over the problem of intermittent locking of a locked oscillator
> > even with a limiter stage present.
>
> That sounds about right, we need a second order loop to ride us through the
> periods of carrier loss, or even effective phase reversal as may happen with
> heavy modulation during selective fading.
I don't care about short wave listening to signals that fade and
amateur radio and so on, I only care about strong local BC band hi-fi
performance. Seems to me there's nothing wrong with envelope detection
with diode + R&C when its done my way with a simple pair of CF. 1 x
12AU7, and that ain't ever going to offend Bean Kounter. The only
exception is when the BC station is at low levels. So "exalted
carrier" is all that's needed, ie, add a 455kHz oscillator signal to
whatever recovered IF signal is there, and effectively reduce the %
modulation of everything detected by the diode + R&C, and thus there's
little distortion to the audio detected if the current discharge from
C is kept nearly constant, thus keeping ripple voltage constant, thus
keeping AF wave close to envelope shape.
So a 455khz oscillator would be good if locked by PLL a highly limited
version of any IF signal present. The limiter could be a pair of 6AU6.
There would be a phase detector tranny, 2 diodes plus some sort of
veractor tuning of oscilator plus a slow time constant filter are
needed. The oscillator can be another 12AU7.
At least 3 tubes are needed.
>
> > But Tucker's radio has its VFO tunable for all of the BC band. This
> > requires a large change in C between say 400pF and 30pF. Let us assume
> > we might find that a limiter stage using a pentode would help to give
> > a better signal to use to lock the VFO, and if you have a tuned VFO
> > with a tuning gang and you have a parallel tuning diode, then getting
> > the C change needed by a Vdc applied might be difficult to get working
> > right, so perhaps all the tuning might be done using a pot and varied
> > DC and nothing but veractors.
>
> Yes, there are certainly problems here, it's not immediately obvious how to
> connect a varactor to the oscillator section of a standard multi gang tuning
> condenser while providing both the needed capacity change at the low end of the
> band, and also not unduly increasing the minimum capacity at the high end of the
> band, that is required to provide the 9:1 capacity change needed to tune the
> entire MW band.
Some tuning diodes give large variations in C. If such diodes are not
used, a mechanical C is used and must have a parallel tuning diode
strapped across it for synchro. The tuning diode must be arrange to
work with its low C value to alter the high end of the band and with
its high C value at the low end.
Don't ask me how, I ain't done it.
But its easy to swing an IF frequency each side of just one F.
>
> This 9:1 impedance change across the band will also affect the gain of the PLL
> circuit, influencing its performance including lock range and stability.
>
> It's not clear to me how much substituting varactors for a mechanical tuning
> gang simplifies the problem, it presumably would if we were willing to use
> opamps and piecewise linear summing circuits in the DC circuits controlling the
> varactors. Maybe there is a simple solution that I am just not seeing.
Most expeditions into chip driven circuits involve simple ideas
achieved with hundreds of devices hidden in the chip. Hence we see a
typical AM/FM radio tuner PCB with so many parts and nobody really
knows what's going on. The chip count is larger than the tube count.
Most people look into a an AM/FM tube tuner and its all baffling. Most
old guys in amateuer radio hate FM, and exclaim, "Damn it man, we just
want F to remain constant." None I ever talked to knew about mutiplex
stereo decoding, and very few knew about TV sets.
But they knew how to turn on the set and tell everyone about their
latest medical condition. I live in a world where most details and
principles behind how most things work are unknown.
I searched for a simple explanation about how digital radio works,
with all waveforms and schematics. No way, its secret stuff. Don't
even try to change anything on the board with several layers and such
small chips with so many pins you can't count them.
>
> In any event there is something very satisfying about a mechanical tuning gang
> in a tube radio.
Indeed.
>
> > I cannot list all forseable bothers trying to do all this.
>
> Yes, while the direct conversion, or ³Zero-IF², approach has a strongly
> seductive allure, its realization does raise a multitude of bothers. I'm not
> sure how common direct conversion radios are outside of the ³Ham² radio
> community, does anyone know? I suspect that most of the so called ³Zero-IF²
> receivers are actually superhetrodynes, where what at one time would have been
> double conversion superheterodynes have had their second IFs replaced with a
> ³Zero-IF² and detector.
>
> All these bothers are why I like my crawl before walking superhetrodyne with PLL
> synchronous detector approach, at least for a first project.
I agree that's the best approach, but you maybe need 3 tube sockets
and a fair bit of skill. Tuckers double balanced ring diode de-
modulator looks simple until you try to make one. Quite a bit about
that on the web now and considerable stuff in british amateur radio
book, RSGB 5th edition, which has stuff with tubes and SS and chips.
Not one single working PLL with tubes for BC band.
>
> > But if it can be done for where VFO must make F between 530kHz and
> > 1,710kHz, then its better to do it than retain the superhet mixer
> > stage, which we might want to chuck out BECAUSE we wish to use a
> > synchrodyne instead, and gain selectivity offered by the audio LPF
> > rather than by the IFT selectivity.
>
> Yes, the direct conversion approach is very seductive, no question. With the
> superheterodyne approach, if you make the IF very wide, perhaps using a 2 MHz
> IF, then you can control the audio bandwidth with the audio LPF just as with the
> direct conversion approach.
And 2MHz IF does mean wide audio BW, but perhaps an extra IF stage, ie
6 tuned circuits to get skirt selectivity are needed. Exalted carrier
at 2MHz with PLL control and envelope detection would work to allow
the extra AF BW without slew.
I have a schematic of a Miller "Hi-fidelity" TRF radio tuner using 4
tuned circuits with a 4 gang cap.
http://www.indianaradios.com/Miller%20570-T%20Hi-Fidelity%20AM%20Tuner.htm
There are 4 RF coils, one per can, 200uH each, arranged in 2 pairs.
with bottoms of the two coils not grounded but are connected to each
other via a 12uH coil with CT which is taken to 0.05uF and the AGC
voltage circuit. I assume the slight mutual coupling improves the
selectivity curves for the claimed 7.5kHz to 10kHz BW while getting
enough skirt selectivity for closest locals which here would be 45kHz
apart.
Many ppl, myself included will have two identical 2 gang caps to make
4 gangs. They may be fairly easily made to have the same sized tuning
wheels and the one dial cord will swing them all the same.
The two tube superhet works well for most ppl for locals if they don't
mind 3kHz AF BW. But it can be made to work a lot better with a
switched tertiary coil on IFT1 to give twin peaked 455kHz which then
widens overall AF BW to 8kHz. Details are in RDH4, and such things
were not uncommon on AM tuners of 1950s and 60s and you'd tune with
the tuning eye on lo-fi, then press the hi-fi button to switch in the
tertiary and BW went to 8kHz. A dedicated tone control could increase
it. The tuner was cheap with just 6BE6, 6BA6. I've done a few samples
with the mod, not bad, and if fitted with the CF detector and ungraded
following audio stages, and with ferrite antenna to minimise hum when
tuned to stations affected by compact fluorescent lamps.
>
> > I do not know if the synchrodyne balanced demodulator can produce a
> > Vdc which may be used for VFO F control in addition to producing audio
> > output.
>
> No, you need separate detectors for the ³PLL² and to recover the audio. The two
> detectors must be provided with carrier signals from the oscillator 90 degrees
> out of phase with each other. Maintaining the required 90 degree phase shift
> over a 3:1 frequency range is another big potential gotcha for a tube based
> direct conversion receiver. In a solid state design this problem would be
> simply dealt with by operating the oscillator at 4 or 8 times the received
> frequency, and using digital dividers to generate the 90 degree phasing between
> the two local oscillator signals. A large number of tubes would probably be
> required to do it this way in a tube based circuit.
>
> You may also want to add a lock detector circuit, and an envelope detector to
> your list above. The lock detector could switch the parameters of the ³Loop
> Filter² when out of lock to facilitate locking, and also switch to an envelope
> detector during tuning.
>
> > But one thing is for sure, to make a synchrodyne with tubes to meet
> > modern use expectations is a real big ask.
>
> Yes, it's a very big ask!
The TRF looks a lot easier. There's always enough signal on strong
locals. No real need for "exalted" carrier injection and envelope
detection, or syncro-anything.
Patrick Turner.
>
> --
> Regards,
>
> John Byrns
>
> Surf my web pages at, http://fmamradios.com/- Hide quoted text -
John Byrns
Patrick Turner <in...@turneraudio.com.au> wrote:
> On Jul 28, 4:08�am, John Byrns <byr...@sbcglobal.net> wrote:
> >
> > That sounds about right, we need a second order loop to ride us through the
> > periods of carrier loss, or even effective phase reversal as may happen
> > with
> > heavy modulation during selective fading.
>
> I don't care about short wave listening to signals that fade and
> amateur radio and so on, I only care about strong local BC band hi-fi
> performance.
At least here in the US, the same sort of distortion from greater than 100%
negative modulation, or skewed sidebands, occurs on local stations if you happen
to be unlucky enough to be in one of the nulls of a directional broadcasting
antenna.
> Seems to me there's nothing wrong with envelope detection
> with diode + R&C when its done my way with a simple pair of CF. 1 x
> 12AU7, and that ain't ever going to offend Bean Kounter. The only
> exception is when the BC station is at low levels. So "exalted
> carrier" is all that's needed, ie, add a 455kHz oscillator signal to
> whatever recovered IF signal is there, and effectively reduce the %
> modulation of everything detected by the diode + R&C, and thus there's
> little distortion to the audio detected if the current discharge from
> C is kept nearly constant, thus keeping ripple voltage constant, thus
> keeping AF wave close to envelope shape.
Sounds good, but you are describing a syncrodyne detector.
> So a 455khz oscillator would be good if locked by PLL a highly limited
> version of any IF signal present. The limiter could be a pair of 6AU6.
> There would be a phase detector tranny, 2 diodes plus some sort of
> veractor tuning of oscilator plus a slow time constant filter are
> needed. The oscillator can be another 12AU7.
> At least 3 tubes are needed.
And presto you have just built the synchronous detector that say isn't needed.
> I have a schematic of a Miller "Hi-fidelity" TRF radio tuner using 4
> tuned circuits with a 4 gang cap.
> http://www.indianaradios.com/Miller%20570-T%20Hi-Fidelity%20AM%20Tuner.htm
I'll raise you two, I have a schematic of a Western Electric TRF radio tuner
using 6 tuned circuits with a 6 gang cap.
http://louise.hallikainen.org/~harold/BroadcastHistory/uploads/We10a.pdf
and
http://www.radiomuseum.org/r/western_el_10_a10.html
> There are 4 RF coils, one per can, 200uH each, arranged in 2 pairs.
> with bottoms of the two coils not grounded but are connected to each
> other via a 12uH coil with CT which is taken to 0.05uF and the AGC
> voltage circuit. I assume the slight mutual coupling improves the
> selectivity curves for the claimed 7.5kHz to 10kHz BW while getting
> enough skirt selectivity for closest locals which here would be 45kHz
> apart.
I have one of these J.W.Miller TRF tuners. To maintain constant bandwidth from
the bottom to the top of the MW broadcast band the circuit Q of the coils must
increase in proportion to the frequency, this can be accomplished by arranging
the circuit so that series resistance, either part of the coil, or external,
dominates the in circuit Q of the coil. Then when coupled into band-pass pairs
the product of the coupling factor k, and the Q, or kQ, must be kept constant
across the MW band. Since the Q is increasing with frequency the coupling
coefficient k must be inversely proportional to frequency. This is done by
keeping the mutual coupling reactance constant across the band. Unfortunately
ordinary capacitors and inductors have reactance which varies with frequency.
This problem is solved by using a normal capacitor in series with an inverse
capacitor who's reactance varies proportionally to frequency, the two
"capacitors" approximating a constant capacitive reactance across the MW band.
The inverse capacitor is simulated by using the so called "negative mutual
coupling coil", the center tapped coil that you describe which acts as the
inverse capacitor in the mutual coupling circuit.
Patrick Turner
> In article <ac0443b1-2a46-4e2e-a64f-6ced3cdb8...@t38g2000prj.googlegroups.com>,
>
> I'll raise you two, I have a schematic of a Western Electric TRF radio tuner
> using 6 tuned circuits with a 6 gang cap.http://louise.hallikainen.org/~harold/BroadcastHistory/uploads/We10a.pdf
>
> > There are 4 RF coils, one per can, 200uH each, arranged in 2 pairs.
> > with bottoms of the two coils not grounded but are connected to each
> > other via a 12uH coil with CT which is taken to 0.05uF and the AGC
> > voltage circuit. I assume the slight mutual coupling improves the
> > selectivity curves for the claimed 7.5kHz to 10kHz BW while getting
> > enough skirt selectivity for closest locals which here would be 45kHz
> > apart.
>
> I have one of these J.W.Miller TRF tuners. To maintain constant bandwidth from
> the bottom to the top of the MW broadcast band the circuit Q of the coils must
> increase in proportion to the frequency, this can be accomplished by arranging
> the circuit so that series resistance, either part of the coil, or external,
> dominates the in circuit Q of the coil. Then when coupled into band-pass pairs
> the product of the coupling factor k, and the Q, or kQ, must be kept constant
> across the MW band. Since the Q is increasing with frequency the coupling
> coefficient k must be inversely proportional to frequency. This is done by
> keeping the mutual coupling reactance constant across the band. Unfortunately
> ordinary capacitors and inductors have reactance which varies with frequency.
> This problem is solved by using a normal capacitor in series with an inverse
> capacitor who's reactance varies proportionally to frequency, the two
> "capacitors" approximating a constant capacitive reactance across the MW band.
> The inverse capacitor is simulated by using the so called "negative mutual
> coupling coil", the center tapped coil that you describe which acts as the
> inverse capacitor in the mutual coupling circuit.
I like the Miller tuner more than I like the other WE sets.
But what you said in your concluding paragraph has an abundance of
information which leaves the obscurity around the subject described at
least highly persistant.
I found the Q got higher at the low end of the BC band so in one radio
I used two input coils and two gangs on one set so that each coil
tuned each side of a centre F at the low end, and both together at the
top end where whatever the Q was, it wasn't enough to cut sidebands
much for the wanted 10kHz of AF BW. The two coils had their own copper
can and were bits of ferrite rod and solid wire. The first had a
loosely coupled input primary winding from a bittowire antenna, with
the tuned winding coupling to the second tuned LC via a carbon comp R
= 39k. Seemed to work just fine. But fluorescent lamps ruined
reception and I changed to one hand made coil on a single ferrite rod.
Audio HF remained OK and hum pissed off, so I is 'appy wiff wotteye
got now.
Patrick Turner.
John Byrns
Patrick Turner <in...@turneraudio.com.au> wrote:
I think you need to use Litz wire instead of solid wire to wind the coils, like
the crystal set guys do, to get the required Q at the high end of the band.
Then add a small series resistor to each coil to reduce the Q at the low end of
the band; this series resistance has little effect at the high end of the band
when variable capacitor tuning is used. Then you need to do some reading on
filter theory to find out the proper way to couple the two coils. This approach
will provide a flatter response, with less finicky alignment and lower losses
than your ad hoc approach.