best AM tube tuner?
romper
I'm interested in finding a good sounding and performing
AM-only tube tuner. Any recommendations would be appreciated.
Ray Parkhurst
rom...@ix.netcom.com
RUINTHERE
There are alot of good ones around. I guess the question is what do you want
to use it for? Listening to , or serious listening. DXing, it all depends on
what you want out of it. Let me know what you want it for and I can tell you
more..
Ruinthere
Nicholas Androulidakis
I'm also interested in one. My priorities are for audio quality not DXing.
Thanks
RUINTHERE <ruin...@aol.com> wrote in article
<19971014051...@ladder01.news.aol.com>...
John Byrns
In article <19971014051...@ladder01.news.aol.com>,
ruin...@aol.com (RUINTHERE) wrote:
> There are alot of good ones around. I guess the question is what do you want
> to use it for? Listening to , or serious listening. DXing, it all
depends on
> what you want out of it. Let me know what you want it for and I can tell you
> more..
>
> Ruinthere
Hi Ruinthere,
The original poster said he was looking for a "good sounding and
performing AM-only tube tuner." I assume from the context, he is talking
about a tuner for serious Hi-Fi listening. In my experience, quality AM
only tube tuners are few and far between, although I am sure there are
those I don't know about. The best AM only tube tuner, is of course the
Western Electric model 10A radio receiver. Unfortunately, these are very
hard to find, and if you can find someone with one to sell, the price is
astronomical. A more recent AM only tube tuner, is the Fisher AM-80. The
AM-80 can be hard to find, but persistence will pay off with one of the
best AM only tube tuners of the modern era. Heathkit had a series of nice
AM only tube tuners. The series of half a dozen or so models, started
with the BC-1A. The BC-1A had only one IF bandwidth, which was designed
for Hi-Fi reception. The Heathkit AM only tube tuners that followed, used
essentially the same circuit as the BC-1A, but added a selectivity switch,
which allowed selection of either a wide IF bandwidth for Hi-Fi reception,
or a narrow IF bandwidth for difficult reception conditions. EICO also
offered an AM only tuner kit, the HFT-94. I didn't much care for this
tuner when I owned one, but that was a long time ago, so my opinion might
be somewhat different if I had one today. With the exception of the WE,
all of these quality AM only tube tuners offer a choice of at least two IF
selectivity's. Quad also offered several models of AM only tube tuners
over the years, which were built to take there power from the Quad 22
preamp. I have not had any experience with the Quad tuner, and so can't
comment on it's performance. I am sure I have missed some, but that
pretty much covers the field of quality AM only tube tuners that I am
aware of.
If one considers AM/FM tube tuners, then there are considerably more
tuners to choose from, with quality AM sections. Both McIntosh, and
H.H.Scott offered AM/FM tube tuners with excellent AM sections. The
Fisher 80-R AM/FM tuner has virtually the same AM circuit as the elusive
AM-80. 80-R's are very common and inexpensive to purchase.
I know there were a lot of AM only tuners of an inferior grade, I would be
interested in hearing about any quality ones I have missed.
Regards,
John Byrns
Randy Nachtrieb
Hi Ned,
The TRF might work OK out in the boonies, but I doudbt it would
have adequate selectivity for an urban area.
You should be careful Ned, what you say I mean, I think I hear the
Major(Armstrong) turning over in his grave.
73,
Randy
Ned Carlson
jby...@enteract.com (John Byrns) wrote:
>
>I know there were a lot of AM only tuners of an inferior grade, I would be
>interested in hearing about any quality ones I have missed.
John:
I'd always heard that TRF tuners had the best fidelity
amongst AM tuners.I remember reading that both Meissner
and J.W.Miller made hifi TRF tuners in the early '50's.
I suppose one could use an Atwater Kent model 40
as an AM tuner, besides being a TRF, it had a single
'71A on the output..I guess one could use a 5K L-pad
to pad down the output. <g>
IMA that I had at one time both a McSomethingorother
TRF console and a Radiola 80.The TRF sounded better, but
the Radiola could actually pick out 660 in NYC in
between 670 (Chicago) and 650 (Nashville),
note I did not live in Chicago at the time, still
it was pretty impressive for a 1929 radio!
Ned Carlson, Triode Electronics, Chicago, IL http://www.triodeel.com
Open 12:30-8 PM CT, 12:30-5 PM CT Sat Closed Wed
ph:773-871-7459 fax 773-871-7938 "where da tubes are"
Email catalogs: email our CataBot: cat...@triodeel.com
John Byrns
> jby...@enteract.com (John Byrns) wrote:
>
> >
> >I know there were a lot of AM only tuners of an inferior grade, I would be
> >interested in hearing about any quality ones I have missed.
>
>
> John:
> I'd always heard that TRF tuners had the best fidelity
> amongst AM tuners.I remember reading that both Meissner
> and J.W.Miller made hifi TRF tuners in the early '50's.
> I suppose one could use an Atwater Kent model 40
> as an AM tuner, besides being a TRF, it had a single
> '71A on the output..I guess one could use a 5K L-pad
> to pad down the output. <g>
> IMA that I had at one time both a McSomethingorother
> TRF console and a Radiola 80.The TRF sounded better, but
> the Radiola could actually pick out 660 in NYC in
> between 670 (Chicago) and 650 (Nashville),
> note I did not live in Chicago at the time, still
> it was pretty impressive for a 1929 radio!
Hi Ned,
Yes, you are right, the TRF makes a better AM standard broadcast band
receiver than does the superhetrodyne. Unlike FM, the superhetrodyne
principal was not one of Major Armstrong's better ideas. The only good
thing about the superhetrodyne is that it gave the RCA one of the tools
they needed to dominate the radio industry. The problem with the
superhetrodyne, is that the frequency conversion process tends to bruise
the modulation. :) Unfortunately in the typical TRF receiver the
selectivity curve has a poor, since single tuned circuits are commonly
used. This results in less than optimum audio frequency response, and/or
poor selectivity depending on the tradeoffs made by the designer.
I did mention the Western Electric model 10A receiver, which is a TRF
tuner. The 10A is a very sophisticated TRF design using 6 tuned
circuits. The 6 tuned circuits are coupled in pairs, to form 3 double
tuned circuits, similar to the IF transformers in a superhetrodyne. By
proper design of the circuits, the Q can be made to increase with
frequency, maintaining a constant bandwidth across the entire AM broadcast
band. It is also necessary to have the coupling coefficient k, vary
inversely with frequency, so that critical coupling can be maintained
across the AM broadcast band. critical coupling is where the product kQ =
1.0. The coupling coefficient is made to vary inversely with frequency by
using "negative mutual coupling coils". The negative mutual coupling coil
acts sort of like a negative capacitor, which when combined with a
standard positive capacitor in a low side coupling arrangement, provides
an approximation of the required inverse relationship of k with
frequency. In this way critical coupling is maintained across the AM
broadcast band, and if the Q is made proportional to frequency, by making
series losses dominate, then the RF bandwidth will remain constant as we
tune across the AM band. Each of these double tuned circuits will have
the same response curve as the IF transformers in a superhetrodyne
receiver. The Q can be made low, with a higher k, for wide bandwidth and
Hi-Fi audio, or higher Q circuits can be used with lower k values, for
better selectivity. This type of circuit can provide the same response
curve, selectivity and bandwidth as a two stage IF amplifier in a
superhetrodyne receiver with 3 IF transformers. Of course there are many
practical problems implementing a design of this sort, and the cost will
be greater than an equivalent superhetrodyne.
The J.W.Miller tuner that you mentioned, uses the same type of negative
mutual coupled, double tuned circuits as the Western Electric receiver.
The J.W.Miller tuner only uses 2 pairs of double tuned circuits however,
while the WE tuner uses 3 pairs of double tuned circuits. The Meissner
tuner used 2 pairs of double tuned circuits like the J.W.Miller tuner, but
they didn't use the "negative mutual coupling" principal, so the Meissner
tuner probably didn't achieve a bandwidth consistency across the AM band,
as good as the WE and Miller tuners.
I am not familiar with the Atwater Kent model 40 receiver you mentioned,
but if it uses single tuned coils, it is not going to have as good an
audio response as the WE and Miller tuners. Of course the WE is a
relatively modern radio, dating from 1931, so it should do better than an
old radio like the 1929 Atwater Kent.
Regards,
John Byrns
Randy Nachtrieb
Hi John,
I think you will be chided by both the General & the Major on this
one.
While perhaps the use of the TRF can be defended for AM broadcast,
regarding superheterodynes; "the frequency conversion process tends to
bruise the modulation" ? If this is true, would it not occur during the
final detection process anyway?
The superheterodyne principle wasn't a very good idea? I think you
would be hard pressed to come up with good multi-band rcvrs, or spectrum
analyzers, among other things we now take for granted, without it. How
would you have been able get the high degrees of selectivity, made
possible by fixed filters, such as the xtal & mechanical types ?
Aside from the generally minor problem of image rejection, what
are the disadvantages of the superheterodyne.
Best Regards,
Randy Nachtrieb
Daniel J. Marshall
John,
Since the BW of a single tuned circuit equals 1/2PICR it follows that
the most straightforward way to maintain a constant bandwidth across the
broadcast band is to use variable inductors for tuning. I have seen
automobile radio tuners constructed in this manner. It seems a wonder
that it never caught on back then. Perhaps there are other
considerations that are not initially apparent.
Dan Marshall
Randy Nachtrieb
Hi John,
I would imagine the E.H. Scott units performed well also.
Best,
Randy
RUINTHERE
I have a radio I rescued from the clutches of the garbage monster (don't we
all) It is going to be a project... It is a Spartan TRF it is a beast huge 4
or 5 gang cap on it lots of ferrite cores too so it probably has a reasonable
Q in the tank ckt. I need a schematic I realizei could probably draw one up
but would like to get real one. I have a ton [ reads alot] of Sams schez's and
some old Rider manuals on early radios. Lot of old stuff,. If anybody is
looking drop me a email. Probably have at least 1000 folders alot of real
early stuff.
Ruinthere
John Byrns
In article <629gqf$ekf$1...@newsd-111.bryant.webtv.net>, gat...@webtv.net
(Randy Nachtrieb) wrote:
Hi Randy,
I thought I included a smilely face in my post for the humor impaired?
With respect to the modulation being bruised in the final detection
process, I look at it sort of like cooking, when you go to the market to
by fruits and vegetables, you try to find specimens that are not seriously
bruised, even though when you get them home, the cooking process may cause
serious trauma to them.
Also I think I was careful to restrict my comments about TRF designs, to
use in the AM standard broadcast band, where the principal is well suited,
if you don't mind the cost.. I explicitly did this because in other
applications, all the things you say are true.
Image rejection is not the only problem superhets have, they are subject
to a whole litany of spurious response problems, which degrade their
performance in critical audio applications.
Regards,
John Byrns
John Byrns
In article <34482D...@worldnet.att.net>, "Daniel J. Marshall"
<danma...@worldnet.att.net> wrote:
> John,
>
> Since the BW of a single tuned circuit equals 1/2PICR it follows that
> the most straightforward way to maintain a constant bandwidth across the
> broadcast band is to use variable inductors for tuning. I have seen
> automobile radio tuners constructed in this manner. It seems a wonder
> that it never caught on back then. Perhaps there are other
> considerations that are not initially apparent.
Hi Dan,
Yes, inductive tuning does appear attractive for this purpose. For years
I thought inductive tuning would be the best way to build a TRF receiver,
and I still would like to try building one that way some day. It should
be noted that your formula for bandwidth applies to parallel resistance,
for series resistance, it is something like R/2PIL. So in either case it
is a matter of designing the circuit so the dominant losses are of the
required type. As far as I know there are two problems with inductive
tuning in a TRF design. The first is cost, I think it is difficult, read
expensive, to maintain the winding pitch within the required tolerances
for good tracking.
The second problem is that you would like to use the coils in coupled
pairs, for the best response shape. Of course even higher order filters
would be better, but even tube superhets rarely use higher order filter
blocks. With capacitor tuning the "negative mutual coupling" scheme
easily gives a good approximation of the inverse relationship required
between frequency and coupling coefficient k for a pair of coupled coils.
With variable inductors, I don't think there is an easy way to achieve the
inverse k versus frequency relationship for a pair of coupled coils. It
has been some time since I have thought about coupled inductively tuned
coils, so I will have to review it, to see that I am not wrong on this.
Regards,
John
John Atwood
jby...@enteract.com (John Byrns) writes:
>In article <627bfq$579$1...@newsd-112.bryant.webtv.net>, gat...@webtv.net
>(Randy Nachtrieb) wrote:
>> Hi John,
>>
>> I would imagine the E.H. Scott units performed well also.
>>
>>
>> Best,
>>
>> Randy
>Hi Randy,
>I don't think of the E.H. Scott units as being "tuners", to me they are
>more in the "Radio" category, although I guess with the two chassis design
>you could call them "tuners". I took "AM-only tube tuner" to mean the AM
>standard broadcast band, which would exclude the E.H.Scott receivers, most
>if not all of which included shortwave. I know "shortwave" is AM, but
>when people say "AM" they generally are talking about the AM standard
>broadcast band. If we let in shortwave receivers, we will have to include
>AM/FM tuners, in which case the question is not nearly as interesting,
>from a collecting point of view. However, from a technical point of view,
>there definately are some interesting AM designs that are not "AM-only".
I'll add my 2 cents on AM tuners, based mainly on my own experience in
fixing up some old ones.
Quite a good AM-only tuner is the Heathkit model from the mid 1950's that
matched their gold pre-amp and FM tuner. It used a tuned RF stage instead
of two IF stages that most other "better" tuners had. Even better is the
AM section of the Heatkit PT-1 ("Professional Tuner 1"). This came out
when early stereo broadcasts were being done with one channel on AM and
the other on FM, so a lot of effort was made to make the AM quality match
the FM. A later version of this same tuner is the AJ-30 (in the Naugahide
Detroit dash-board styling). The early Fisher tuners had quite good AM
sections, too.
If you want sheer sensitivity and selectivity, the older shortwave receivers
are good. Since many of these have line outputs, they could be classified
as tuners. The National HRO-60 and Hammarlund SP-600 are ledendary. Collins
made several series of recievers, both in commercial and military models.
The ultimate is the R-390 series, but the older 51J3/R-388 is pretty good.
The later model Collins receivers (51J4, R-390A) had mechanical filters,
which, although giving razor-sharp selectivity, don't give as clear audio.
The older, LC IF strips (in the R-388 and R-390) have better sound. By the
way, none of the Collins receivers had decent audio output stages, but if
you tap off the audio before the output, they can sound good.
Despite the backround noise and atmospheric propagation effects, AM radio
listening can be rewarding. The programming is a lot more diverse than on
the FM band, and if you are lucky, you can hear programming through some
great all-tube transmitters that used tubes that would make single-ended
amp audiophiles envious.
- John Atwood
(e-mail replies to atw...@one-electron.com)
--
John Atwood
Preferred e-mail address: atw...@one-electron.com
John Byrns
In article <jatwoodE...@netcom.com>, jat...@netcom.com (John
Atwood) wrote:
> I'll add my 2 cents on AM tuners, based mainly on my own experience in
> fixing up some old ones.
>
> Quite a good AM-only tuner is the Heathkit model from the mid 1950's that
> matched their gold pre-amp and FM tuner. It used a tuned RF stage instead
> of two IF stages that most other "better" tuners had. Even better is the
> AM section of the Heatkit PT-1 ("Professional Tuner 1"). This came out
> when early stereo broadcasts were being done with one channel on AM and
> the other on FM, so a lot of effort was made to make the AM quality match
> the FM. A later version of this same tuner is the AJ-30 (in the Naugahide
> Detroit dash-board styling). The early Fisher tuners had quite good AM
> sections, too.
Hi John,
Yes the Heathkits are very nice, I mentioned them in my first post in this
thread. I think all the Heathkit AM-only tube tuners use the same circuit
that appeared in the "gold" BC-1A you mention. I have a AJ-10, which I
think was the follow on to the BC-1A, with the black with gold vein
styling. Next came the AJ-21, which was the same thing in the Detroit
dashboard style. I have heard that the AJ-53 may also be part of this
tuner family, although I don't know what it looks like. There were a
couple of changes incorporated in the AJ-10 and later models. The BC-1A
used an external shielded loop for an antenna, while the AJ-10 and later
models used a built in ferrite loopstick antenna. The BC-1A had a single
fixed IF bandwidth, which was wide for Hi-Fi reception. The AJ-10 and
later models added a selectivity switch to the first IF transformer, to
provide a narrow bandwidth capability for difficult reception conditions.
From the descriptions of the PT-1, AJ-30, and other Heathkit AM/FM tuners
of that era, it sounds to me like they used the same AM circuitry as was
used in the AM-only models. The only difference I can see in the AM/FM
models, is that they included an AM tuning indicator, either a meter, or
an eye tube, depending on the model. For some strange reason, none of the
AM only models included a tuning indicator.
Most of the "better" AM tuners had a tuned RF stage, even those with two
IF stages like the Fisher. Relatively few quality AM tuners seem to have
used two IF stages, and almost none that I am aware of didn't have a tuner
RF stage.
Regards,
John Byrns
Randy Nachtrieb
Hi John,
I think in this case, the fruit will be bruised when it's picked
from the tree.
It appeared that you were denouncing the superhet idea in general.
Afterall, the Major may be dead, but he's sensitive.
Best,
Randy
John Atwood
jby...@enteract.com (John Byrns) writes:
>From the descriptions of the PT-1, AJ-30, and other Heathkit AM/FM tuners
>of that era, it sounds to me like they used the same AM circuitry as was
>used in the AM-only models. The only difference I can see in the AM/FM
>models, is that they included an AM tuning indicator, either a meter, or
>an eye tube, depending on the model. For some strange reason, none of the
>AM only models included a tuning indicator.
Actually, the Heathkit PT-1 and AJ-30 have a fairly elaborate AM section,
using the following tube line-up:
6BA6 - RF Amplifier
6BE6 - Converter
6BA6 - 1st IF Amplifier
6BA6 - 2nd IF Amplifier
two "crystal rectifiers" - full-wave detector
6AU6 - AVC Amplifier
1/2 12AU7 - AVC Rectifier
1/2 12AU7 - Meter Amplifier
1/2 12AU7 - AF Cathode follower
This is just the AM section. There are nine more tubes for the FM section!
The separate AVC IF amplifier is a feature usually only found in some
communications receivers. When a stereo de-multiplexer was included in
Heathkit's later tube tuners, the AM section was substantially scaled-back.
Nonetheless, the gold BC-1A is still pretty good. I use one of them and a
Radio Craftsmen "Concerto" (a P-P 6V6 integrated mono amp) as my bedside
radio - leading me to scan late-night AM whenever I have insomnia :-)
- John Atwood
SBench
John Burns wrote.....
>I often wonder though, if AM tuners with 4 stages like this aren't a bit
>much? Individually I can see the justification for each stage, but the
>combination seems excessive. Four stages seem like an awful lot of gain,
>especially when you consider that two stages, a 6BE6 Converter, and 6BA6
>IF amplifier will give you all the gain you need for most AM reception
>situations. Of course there are other problems with the two tube design,
>and in fixing them we end up adding two more stages, and along with them
>some new problems. I wonder if there isn't a better way to do it?
>Probably not with common low cost components. Maybe a little out of the
>box thinking is needed here.
>
>
>Regards,
>
>John Byrns
>
>
Hi John,
Don't forget many auto radios had a second IF stage
and most had an RF stage.
I kinda cut my teeth on a couple of old Fada 6 tube AC/DC
critters, one had 2 IF stages and the other an RF and an IF
stage. Both performed better than the "conventional" 5 tube
designs. The RF-Conv-IF could be jimmied up into SW without
running out of gas, and the selectivity of the 2 IF critter had
wonderful selectivity for AM DXing. If I really look thru the
old junkbox, still MIGHT have one of those chassis (or at least
bits of it).
Steve
Ned Carlson
gat...@webtv.net (Randy Nachtrieb) wrote:
>Hi Ned,
>
> The TRF might work OK out in the boonies, but I doudbt it would
>have adequate selectivity for an urban area.
I beg to differ, Randy. The difference in strength between stations
of similar frequency would have been much greater in urban
areas (read:Chicago, NY, LA).. Example, the Chicago
ones, spaced at 550,670,720,780,820, 1000, & so forth.
Thus the popularity of the cheeseball 1930's 4 tube plus ballast
(or worse 4 tubes plus the life threatening "resistor line cord")
TRF Walgreens sets (aka "Aetna"). No problem with selectivity
when the stations are at least 40 Khz apart, and the thing's too weak
to pick up out of town stations.
> You should be careful Ned, what you say I mean, I think I hear the
>Major(Armstrong) turning over in his grave.
I doubt it, since I gave credit to his creation being able to pick
out WABC (?) 660 in between WSM 650 and WMAQ 670.
Amazing for a superhet using a '27 oscillator and '24A mixer
and a 175 (? do I remember that correctly?) KHz IF strip,
built in 1929...
Ned Carlson
ruin...@aol.com (RUINTHERE) wrote:
>I have a radio I rescued from the clutches of the garbage monster (don't we
> all) It is going to be a project... It is a Spartan TRF it is a beast huge 4
> or 5 gang cap on it lots of ferrite cores too so it probably has a reasonable
> Q in the tank ckt.
So how old IS it? Some of the really old Spartons aren't TRF's,
instead they use a bandpass filter ahead of a broadband RF amplfier.
Some use really weirdo Sparton tubes, like 484 and 485, which
won't be cheap unless you dig in dumpsters from Denver to Detroit.
(Just be glad it doesn't use Kellogg tubes...)
> I need a schematic I realizei could probably draw one up
> but would like to get real one. I have a ton [ reads alot] of Sams schez's and
> some old Rider manuals on early radios.
If you have a model number, this poor old lady will take a few bucks
off your hands for a diagram:
Steinmetz
219-931-9316
Ned Carlson
jby...@enteract.com (John Byrns) wrote:
>Yes, you are right, the TRF makes a better AM standard broadcast band
>receiver than does the superhetrodyne. Unlike FM, the superhetrodyne
>principal was not one of Major Armstrong's better ideas. The only good
>thing about the superhetrodyne is that it gave the RCA one of the tools
>they needed to dominate the radio industry.
Awww..gimme a break, John, name *one* piece of halfway serious
recieving equipment, from AM to satellite, that *doesn't*
use the superhetrodyne principle. Heck, even cheap stuff, like
cheesy Walkmans.
Superhet was the Major's great legacy to the teeming millions,
one that almost all of them use every day, including the
aforementioned Walkmans, and dang near every AM/FM & TV set
I can think of....
>The problem with the
>superhetrodyne, is that the frequency conversion process tends to bruise
>the modulation. :) Unfortunately in the typical TRF receiver the
>selectivity curve has a poor, since single tuned circuits are commonly
>used. This results in less than optimum audio frequency response, and/or
>poor selectivity depending on the tradeoffs made by the designer.
>I did mention the Western Electric model 10A receiver, which is a TRF
>tuner.
>previous post snipped for brevity>
Frankly, I did not know that the WE10A reciever was TRF.
Considering Bell Labs' near obsessive penchant for Absolute Fidelity
(not that I would criticize that, say, ya got a WE10A you wanna
sell cheap??), it would not surprise me a bit.
> This type of circuit can provide the same response
>curve, selectivity and bandwidth as a two stage IF amplifier in a
>superhetrodyne receiver with 3 IF transformers. Of course there are many
>practical problems implementing a design of this sort, and the cost will
>be greater than an equivalent superhetrodyne.
>The J.W.Miller tuner that you mentioned, uses the same type of negative
>mutual coupled, double tuned circuits as the Western Electric receiver.
>The J.W.Miller tuner only uses 2 pairs of double tuned circuits however,
>while the WE tuner uses 3 pairs of double tuned circuits. The Meissner
>tuner used 2 pairs of double tuned circuits like the J.W.Miller tuner, but
>they didn't use the "negative mutual coupling" principal, so the Meissner
>tuner probably didn't achieve a bandwidth consistency across the AM band,
>as good as the WE and Miller tuners.
>
>I am not familiar with the Atwater Kent model 40 receiver you mentioned,
>but if it uses single tuned coils, it is not going to have as good an
>audio response as the WE and Miller tuners. Of course the WE is a
>relatively modern radio, dating from 1931, so it should do better than an
>old radio like the 1929 Atwater Kent.
>
>
>Regards,
>
>John Byrns
Ned Carlson, Triode Electronics, Chicago, IL http://www.triodeel.com
Randy Nachtrieb
Hi Ned,
The Major forgives the earlier TRF heresy. But a 6:1 skirt
selectivity requirement (for 40khz spacing), isn't very high
performance.
73,
Randy
John Byrns
> So how old IS it? Some of the really old Spartons aren't TRF's,
> instead they use a bandpass filter ahead of a broadband RF amplfier.
> Some use really weirdo Sparton tubes, like 484 and 485, which
> won't be cheap unless you dig in dumpsters from Denver to Detroit.
> (Just be glad it doesn't use Kellogg tubes...)
Hi Ned,
Why doesn't the "bandpass filter ahead of a broadband RF amplfier"
receiver count as a TRF type receiver? I would define TRF as just about
any radio in which all the RF amplification, and selectivity occurs at the
frequency of the transmitted signal. Also the detector must not be a
coherent type of demodulator. How would you define a TRF receiver?
Regards,
John Byrns
Ned Carlson
jby...@enteract.com (John Byrns) wrote:
>Hi Ned,
>
>Why doesn't the "bandpass filter ahead of a broadband RF amplfier"
>receiver count as a TRF type receiver?
Perhaps I should have said not a TRF reciever the way that
most people (at least not me) would think of one.
>I would define TRF as just about
>any radio in which all the RF amplification, and selectivity occurs at the
>frequency of the transmitted signal. Also the detector must not be a
>coherent type of demodulator. How would you define a TRF receiver?
My interpretation of a typical one is like that old AK-40: a tuning
cap & RF xfmr between each tube in the RF strip.
I guess a Sparton like as I described would qualifyas a TRF too,
I just wanted to tell the guy that what he had might not
be what he would expect.
Randy Nachtrieb
Hi Ned,
I was being somewhat facetious, regarding your "praise" for the
TRF.
Best,
Randy
Blondie
I'm trying to convert a Jolida 302A from ultra-linear to triode. Using
EL34's, the 4th pin is the screen. Triode operation means that this should
not be used. Right now, this pin is connected to the 6th pin via a a short
jumper. Now, the question: If I'm removing this cable, should both the 4th
and the 6th pin be left without any connection what-so-ever, or do I have
to do something else?
Please help me in my confusion!
Jan
Andy
On 24 Oct 1997 08:24:14 GMT, ven...@tsb.weschke.com (Lz) wrote:
> Jan
>From the Philips Electron Tube Handbook I (1964)
>
>EL34
>
>pinout: or:
> 4 5 g2 g1
>
> 3 a
>
> 2 7 f f
>
> 1 8 g3 k
>
>
>for triode operation you want the thrid grid (pin 3) connected to the
>katode and the second grid (pin 4) connected to the anode.
> ________
> I I
> _I_ I
> _ _____ I
> I _____ _I
>______(_ _____
> I__ ___
> -^-
>
>something like that.
>
>Lz
Whoa! I just did a Dyna ST-70 and I didn't do whatever it is
you just said. I dropped the Ultralinear tap from pin 4 and soldered
a 1/2 watt 100ohm resister between pins 3 and 4. Works fine... Sounds
much better.
Andy
Ned Carlson
gat...@webtv.net (Randy Nachtrieb) wrote:
>Hi Ned,
>
> I was being somewhat facetious, regarding your "praise" for the
>TRF.
Ooops, *I* ought to recognize facetious when I see it...