Antenna ferrite loopsticks verses air core?

[billbowden]

Which is a better design. Suppose you have a 6 inch length of PVC pipe with
numerous turns of wire that has an inductance of say 200uH. Now suppose you
use the same (6 inch) piece of PVC with a ferrite rod in the core with
considerably fewer turns of wire. Which one would capture the most signal
at the AM Broadcast frequencies (500K to 2 Megs) and poduce the greatest
signal output? Would it be more ferrite, or more wire?

[John Robertson]

Considering that all portable transistor radios I've ever seen had
ferrite core antennas I would assume (not have the math) that ferrite is
more efficient in small spaces. I don't think the price of the copper
wire back in the 50s and 60s would make enough difference to prefer
ferrite over copper wire...

John

[Phil Allison]

** Your Q is stupid, ferrite antennas must have the wire wound on the rod.

Woven, frame antennas like this were used in compact and portable tube radios until the arrival of ferrite rods.

https://s-media-cache-ak0.pinimg.com/736x/06/4b/b1/064bb104c1c02a095ae2cdeaf60faaa1.jpg

Their performance was comparable with a ferrite rod antennas of similar length - the ferrite job having rather higher Q due to using less wire.

Most frame anttennas use "Litz" wire to improve the Q - as did ferrite equivalents.


FYI

Q = ratio of resistance ( at radio frequencies) to inductance.



.... Phil

[rickman]

You are asking how the antenna output voltage varies with the mu of the
inductor core if the inductance is held constant by varying the number
of turns of wire.

The signal strength is related to number of turns linearly as well as
the core permeability. I'll use the tilda to indicate proportionality.

E ~ N * mu

Inductance is proportional to the square of the number of turns and the
permeability.

L ~ N^2 * mu

So when a magnetic core is added the number of turns required to
maintain the inductance is reduced by the square root of the relative
permeability.

N ~ sqrt(mu(rel))

The impact on the received voltage will be reduced by the square root of
the relative permeability through the turns change, but increased
linearly by the change in mu resulting in an overall increase in
received voltage by the square root of the relative permeability.

So adding a material with mu(rel) of 4.0 will cut the number of turns in
half and increase the output voltage by 2. This doesn't include an
improvement in the resistive losses of the coil. The Q of the coil will
be reduced as the inductance drops linearly, but the resistance goes
down by the square root of the permeability.

--

Rick C

[mako...@yahoo.com]

>
> So adding a material with mu(rel) of 4.0 will cut the number of turns in
> half and increase the output voltage by 2. This doesn't include an
> improvement in the resistive losses of the coil. The Q of the coil will
> be reduced as the inductance drops linearly, but the resistance goes
> down by the square root of the permeability.
>
> --
>
> Rick C

And in the AM broadcast band, the SNR is usually not determined by the radio but rather by the atmospheric noise and interference form other stations,,,, so even though you may build an antenna that puts out more "volts" it will not be helpful for picking up weaker signals.

M

[Dave M]

It is much more likely that higher inductance is needed at AM broadcast
frequencies in order to keep the tuning capacitaance at a reasonably low
value and because of limited space in a portable or tabletop radio.

Dave M

[John Larkin]

A ferrite rod sucks up and concentrates the H field. More flux passes
through the core than if the same geometry were all air. And it needs
a lot less copper to sample that field, an to make a nice inductance
to resonate.

In your case, use a smaller winding directly on the rod or (harder to
do) fill the entire insides of the tube with ferrite.

The rod inserted into your pipe and winding will increase the flux,
but it's not optimum. The people who have been making radios for close
to a century have probably optimized the design.




--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[Tim Wescott]

On Wed, 15 Mar 2017 08:25:25 -0700, John Larkin wrote:

> The people who have been making radios for close to a century have
> probably optimized the design.

Optimized for cost to sales ratio, certainly, but maybe not for the best
performance to size ratio.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

[billbowden]

"Phil Allison" <palli...@gmail.com> wrote in message
news:fde659de-674b-4ce5...@googlegroups.com...

> Bill Bowden wrote:
>>
>> Which is a better design. Suppose you have a 6 inch length of PVC pipe
>> with
>> numerous turns of wire that has an inductance of say 200uH. Now suppose
>> you
>> use the same (6 inch) piece of PVC with a ferrite rod in the core with
>> considerably fewer turns of wire. Which one would capture the most
>> signal
>> at the AM Broadcast frequencies (500K to 2 Megs) and poduce the greatest
>> signal output? Would it be more ferrite, or more wire?
>>
>
> ** Your Q is stupid, ferrite antennas must have the wire wound on the rod.
>

Well, I can't help it if I'm stupid. I was just born that way. And I did
assume the wire should be wound around the ferrite rod usually using Litz
wire to reduce the skin effect. But there are some eddy current losses in
the ferrite and I was just wondering if you knew how much that woud be?

[billbowden]

<mako...@yahoo.com> wrote in message
news:02d0a874-f95c-40ef...@googlegroups.com...

Yes, that's true. It really doesn't matter what the signal strength is, only
how much additional noise you introduce into the system.

[billbowden]

"rickman" <gnu...@gmail.com> wrote in message
news:oaanum$upg$1...@dont-email.me...

So, I think you are saying adding more ferrite into the core and reducing
turns of wire has some signal level advantage? But considering SNR, it
doesn't much matter?

[rickman]

If you are building a coil to a specific inductance, then yes, you get
more signal with a ferrite core but the difference is not a lot.

The issue of SNR depends on many factors. You still need a low noise
first amplifier to raise a small signal from an antenna. The point is
that if you have an adequately large signal from the antenna already, a
lower noise in the amp won't be useful as the noise in the signal will
be much greater. But that depends on the specifics of your signal field
strength, the signal SNR, the effective height of the antenna (how well
it converts the field strength to volts) and the noise level of your
receiver front end. How many of these do you know?

BTW, the coil does not need to be wound literally on the core. I've
seen many antennas that were wound on a cardboard or plastic tube with
the ferrite not tight inside. I can only assume they did that to make
the manufacturing easier.

--

Rick C

[Phil Allison]

Bill Bowden wrote:

>
> ** Your Q is stupid, ferrite antennas must have the wire wound on the rod.
>
>
> Well, I can't help it if I'm stupid.

** But you can piss off and stop being a PITA troll.

> I was just born that way.

** No excuse for you to go around annoying people.

> And I did
> assume the wire should be wound around the ferrite rod usually using Litz
> wire to reduce the skin effect.
>

** No way anyone can know what you claim you assumed but did not post.

And you can make up *any damn shit* later.

> But there are some eddy current losses in
> the ferrite and I was just wondering if you knew how much that woud be?

** That is nothing like your original Q and no question was directed at me.

You do NOT direct questions at posters except to explain what they have posted. All other question are directed to the group.

You are making shit up, moment to moment.

Kindly fuck off.


.... Phil

[Phil Allison]

mako...@yahoo.com wrote:
>
>
> And in the AM broadcast band, the SNR is usually not determined by the
> radio but rather by the atmospheric noise and interference form
> other stations,,,,
>

** Providing there is an adequate signal from the antenna carrying the wanted broadcast.

> so even though you may build an antenna that puts out more "volts"
> it will not be helpful for picking up weaker signals.

** Complete non-sequitur and obviously false.



..... Phil

[Phil Allison]

Dave M wrote:
>
>
> It is much more likely that higher inductance is needed at AM broadcast
> frequencies in order to keep the tuning capacitaance at a reasonably low

> value ...
>

** Most AM sets have an antenna coil or tuned transformer for that.

A ferrite or woven frame antenna is tuned directly by the tuning gang.




.... Phil

[Phil Allison]

Tim Wescott wrote:
>
>
> > The people who have been making radios for close to a century have
> > probably optimized the design.
>
> Optimized for cost to sales ratio, certainly, but maybe not for the best
> performance to size ratio.
>

** The latter is exactly what a ferrite antenna is optimised for.


.... Phil

[Phil Allison]

Prickman wrote:
>
>
> BTW, the coil does not need to be wound literally on the core. I've
> seen many antennas that were wound on a cardboard or plastic tube with
> the ferrite not tight inside. I can only assume they did that to make
> the manufacturing easier.
>

** Wrong assumption.

If you knew a damn thing about AM radios, you would know that the coil is made *movable* on the rod so it's inductance can be adjusted to peak resonance with the frequency being received.

Normally, you do this at the bottom of the band and use a trimmer cap for the top end. The coil is then held in place with melted wax or similar.



.... Phil

[John Larkin]

In the early days of transistor radios, size was limited and gain was
expensive, so it was worth some ferrite to get more RF input power.
Gain is now so cheap that an air core antenna might be OK.

--

John Larkin Highland Technology, Inc

picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

[Phil Allison]

John Larkin wrote:
>
> >>
> >> > The people who have been making radios for close to a century have
> >> > probably optimized the design.
> >>
> >> Optimized for cost to sales ratio, certainly, but maybe not for the best
> >> performance to size ratio.
> >>
> >
> >** The latter is exactly what a ferrite antenna is optimised for.
> >
> >

> In the early days of transistor radios, size was limited and gain was
> expensive, so it was worth some ferrite to get more RF input power.
> Gain is now so cheap that an air core antenna might be OK.
>

** Really ?

Try posting an idea that is not full of ambiguities.


... Phil

[amdx]

On 3/14/2017 11:18 PM, billbowden wrote:
> Which is a better design. Suppose you have a 6 inch length of PVC pipe with
> numerous turns of wire that has an inductance of say 200uH. Now suppose you
> use the same (6 inch) piece of PVC with a ferrite rod in the core with
> considerably fewer turns of wire. Which one would capture the most signal

> at the AM Broadcast frequencies (500K to 2 Megs) and produce the greatest

> signal output? Would it be more ferrite, or more wire?
>
>

It seems to be more ferrite. The latest and greatest ferrite antenna
is the Ferrite Sleeve Loop (FSL). It uses multiple rods, or bars
arranged side by side in a circle with wire wrapped around it.
Diameters range from 5" to 15" although one day someone will spend the
money to make 20"
Here's one that that is 7" in diameter and uses 68-5/16" diameter rods
5" in length.
> http://www.thomasn.sverige.net/7_Inch_Affordable_FSL.pdf

Optimization of Ferrite Sleeve Antenna.
> http://www.am-dx.com/antennas/FSL%20Antenna%20Design%20Optimization.htm
Lots of comparison data here.

For determination of the design factors influencing an FSL antenna’s
weak-signal performance, four of the FSL test model match ups were
considered very important. These four match ups (with the design factors
clarified by the results) were as follows:

Followup on the link.

Search FSL for more info, Gary Debock is an experimenting guru.
Mike














---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

[billbowden]

"Phil Allison" <palli...@gmail.com> wrote in message

news:7108a9ca-3ab7-423b...@googlegroups.com...

> Bill Bowden wrote:
>
>>
>> ** Your Q is stupid, ferrite antennas must have the wire wound on the
>> rod.
>>
>>
>> Well, I can't help it if I'm stupid.
>
> ** But you can piss off and stop being a PITA troll.
>
>> I was just born that way.
>
>
> ** No excuse for you to go around annoying people.
>
>> And I did
>> assume the wire should be wound around the ferrite rod usually using Litz
>> wire to reduce the skin effect.
>>
>
> ** No way anyone can know what you claim you assumed but did not post.
>

Go read the original post. I clearly asked which was better, an air core
inductor or a ferrite core of the same size . The answer should be yes this
and not that, but you don't have any idea. You are just a bozo. .

> And you can make up *any damn shit* later.
>
>
>> But there are some eddy current losses in
>> the ferrite and I was just wondering if you knew how much that woud be?
>
>
> ** That is nothing like your original Q and no question was directed at
> me.
>
> You do NOT direct questions at posters except to explain what they have
> posted. All other question are directed to the group.
>

Well, I'm directing the question to you since you seem to know everything.
And BTW, I worked in a radio factory and adjusted maybe 1000 antenna
loopsticks in transistor radios and peaked the trimmer caps at the top end
and moved the coil winding on the ferrite rod at the low end to get best
performance across the band. I'm not a novice. So, why don't you fuck off?
. .

[Phil Allison]

Bill Bowden the Fuckwit LIAR wrote:


> >
> >
> > ** No excuse for you to go around annoying people.
> >
> >> And I did
> >> assume the wire should be wound around the ferrite rod usually using Litz
> >> wire to reduce the skin effect.
> >>
> >
> > ** No way anyone can know what you claim you assumed but did not post.
> >
>
> Go read the original post.

** Go fuck yourself - moron.

> >
> >> But there are some eddy current losses in
> >> the ferrite and I was just wondering if you knew how much that woud be?
> >
> >
> > ** That is nothing like your original Q and no question was directed at
> > me.
> >
> > You do NOT direct questions at posters except to explain what they have
> > posted. All other question are directed to the group.
> >
>
> Well, I'm directing the question to you since you seem to know everything.
>

** You just posted the DIRECT opposite.

You are pathetic moron and TROLL.

> And BTW, I worked in a radio factory and adjusted maybe 1000 antenna
> loopsticks in transistor radios and peaked the trimmer caps at the top end
> and moved the coil winding on the ferrite rod at the low end to get best
> performance across the band. I'm not a novice.
>

** But you ARE a complete MORON !!!

FFS - FOAD



..... Phil

[Tim Williams]

Reasonable enough. The middle of the ferrite doesn't do you any good; in
fact, after enough size, it's a complete drag on the system -- core losses,
skin effect and dielectric loss take over!

Ferrite isn't as conductive as iron, but it still needs to be laminated if
you want to use really thick sections of it at the same frequencies as
usual.

This is the fundamental behind why different shapes of ferrite beads have
different impedance plots, despite being the same material. Thicker and
longer beads have an impedance peak at lower frequencies; the length and
frequency correspond to the speed of light in the material.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com


"amdx" <noj...@knology.net> wrote in message
news:oacsk7$42q$1...@dont-email.me...

[rickman]

> .. .

>
>> You are making shit up, moment to moment.
>>
>> Kindly fuck off.

Good old Phil is not anyone you should worry with. He may know some
stuff, but his manner is such that he is best killfiled. That's what I
do. I see that he makes posts, but they are marked as having been read.
I very, very seldom bother to read any of his crap, even when someone
else quotes him.

--

Rick C

[Phil Allison]

Prickman the Idiot wrote:




> >> You are making shit up, moment to moment.
> >>
> >> Kindly fuck off.
>
> Good old Phil is not anyone you should worry with.
>

** And not someone to be messed with either.

Prickman is a stupid, bullshitting ass.

And an incorrigible, PITA troll on the NG.

He has ben proven 100% wrong thousands of times.

FFS, DO NOT BELIVE anything the wanker posts



.... Phil


..... Phil

[whit3rd]

On Tuesday, March 14, 2017 at 9:18:38 PM UTC-7, Bill Bowden wrote:
> Which is a better design. Suppose you have a 6 inch length of PVC pipe with
> numerous turns of wire that has an inductance of say 200uH. Now suppose you

> use the same (6 inch) piece of PVC with a ferrite rod in the core ...

There's no comparison. That's because the two antenna designs have
completely different impedances, and must feed entirely different
frontend RF amps. At some frequency, with some particular input
gain stage, you can't just swap those two antennas: you need to redesign
the next stage as well.

[upsid...@downunder.com]

The gain ( = directivity x efficiency) for a typical loopstick is
very bad in the order of -60 to -80 dB, due to the extremely low
efficiency. But thanks to the extremely high band noise at LF and MF,
you still get usable SNR with such designs.

[rickman]

Or you simply couple the antenna to the receiver appropriately.

--

Rick C

[Phil Allison]

whit3rd wrote:

> On Tuesday, March 14, 2017 at 9:18:38 PM UTC-7, Bill Bowden wrote:
> > Which is a better design. Suppose you have a 6 inch length of PVC pipe with
> > numerous turns of wire that has an inductance of say 200uH. Now suppose you
> > use the same (6 inch) piece of PVC with a ferrite rod in the core ...
>
> There's no comparison.
>

** You have **over-snpped** and ruined the OP's question.

> That's because the two antenna designs have
> completely different impedances,

** The ferrite one will have a higher Q, but similar impedance.



..... Phil

[Phil Allison]

upsid...@downunder.com wrote:
>
>
>
> The gain ( = directivity x efficiency) for a typical loopstick is
> very bad in the order of -60 to -80 dB,
>

** Compared to what ???

A half wave antenna 150 meters long?

> But thanks to the extremely high band noise at LF and MF,
> you still get usable SNR with such designs.

** This is not right.

Whatever the inherent atmospheric noise at MF, the signal from the transmitter can over-ride it.

AM does not have inherently bad s/n unless you are DXing.

I have a hi-fi AM tuner that coupled with small frame antenna ( 40x40 cm) is capable of FM like results from good, local broadcasts.

It uses just 2 small valves.



.... Phil

[amdx]

I'll disagree with you on that Phil, I recently built 5 coils
using 6" polystyrene pipe coupler as a form. I wound them with 660/46
wire with spacing's of 11 Turns Per Inch, 12 TPI, 13 TPI, 14 TPI and 15
TPI. All coils were between 232uh and 237uh.
10 TPI, 11 TPI and 12 TPI were pretty close, with Q at 500kHz of 1250,
peaking at about 750kHz with a Q of 1450 and dropping to 950 at 1600kHz.
I used a Boonton 260A Q meter and averaged 5 tests, I'll give the
caveat that high Q's are elusive to measure.
Your standard 61 material is to lossy to get this high, there is some
lower loss material coming out of China that is performing well. The
best I ever got with a #61 material was 550 Q.
Now to defeat my argument, a Chinese radio amateur made a rod with 26
toroids with a Teflon core and Teflon spacers and two parallel 660/46
litz wires, measured peak Q just over 1812.
Then another another duplicated his experiment and got peak Q of 2026.
The material is coming from China and is R40C1.
Details here,
> http://theradioboard.com/rb/viewtopic.php?f=2&t=7058

Proving at least some of the human race, has a lot of free time.

Mikek
Helmet and flak jacket in place.

[John Larkin]

Maybe I should have used shorter words?

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[George Herold]

I've got an AM radio that came with an air core antenna.
(1990's vintage)
~4" (10 cm) squarish loop. Not sure how many turns.
Works fine.

George H.

[John Larkin]

Yes. Gain is cheap now.

(sorry, Phil, one of those words has 5 letters.)

--

John Larkin Highland Technology, Inc

[amdx]

Please don't abuse Phil, he's our entertainment.
Mikek

[Bill Beaty]

> Which one would capture the most signal at the AM Broadcast frequencies

Is your real question , how do we optimize electrically-small 500KHz loop antennas?

:)

First, for electrically-small resonant antennas, increasing the Q will both narrow the bandwidth as well as increasing the total received microwatts. Between ferrite versus air-core loops, which one has more loss-ohms (including ferrite losses, tuning capacitor slider resistance)?

Second, PHYSICAL SIZE makes a big difference. Wind your air-core antenna as a hoop-style, 5ft diameter! Or, use a 5ft ferrite rod with the windings in the center. Both are roughly equivalent (where ideally you'd use 1/2 wavelength, 300 meters @500Khz, not 5ft.)

[John Larkin]

On Thu, 16 Mar 2017 12:12:14 -0700 (PDT), Bill Beaty
<bi...@eskimo.com> wrote:

>> Which one would capture the most signal at the AM Broadcast frequencies
>
>Is your real question , how do we optimize electrically-small 500KHz loop antennas?
>
>:)
>

Start by defining optimum.

[amdx]

On 3/16/2017 3:06 PM, John Larkin wrote:
> On Thu, 16 Mar 2017 12:12:14 -0700 (PDT), Bill Beaty
> <bi...@eskimo.com> wrote:
>
>>> Which one would capture the most signal at the AM Broadcast frequencies
>>
>> Is your real question , how do we optimize electrically-small 500KHz loop antennas?
>>
>> :)
>>
>
> Start by defining optimum.
>
>

He did, as did the op, (capture the most signal)
The next thing is to eliminate transmitted signals you don't want.
You can reduce one lobe of the figure 8 by phasing with a vertical.
Other than that not a lot you can do until you start getting a healthy
part of a wavelength distance between antennas.

[Phil Allison]

John Larkin wrote:
>

> >> >
> >> >** The latter is exactly what a ferrite antenna is optimised for.
> >> >
> >> >
> >> In the early days of transistor radios, size was limited and gain was
> >> expensive, so it was worth some ferrite to get more RF input power.
> >> Gain is now so cheap that an air core antenna might be OK.
> >>
> >
> >** Really ?
> >
> > Try posting an idea that is not full of ambiguities.
> >
>

> Maybe I should have used shorter words?
>

** Express you idea clearly or fuck off.

I know already you will do neither.

You pompous, bullshitting ass.



..... Phil

[Phil Allison]

George Herold wrote:

>
> > >
> > >> In the early days of transistor radios, size was limited and gain was
> > >> expensive, so it was worth some ferrite to get more RF input power.
> > >> Gain is now so cheap that an air core antenna might be OK.
> > >>
> > >
> > >
> > >** Really ?
> > >
> > > Try posting an idea that is not full of ambiguities.
> > >
> > >
> >
> > >
> >

> > Maybe I should have used shorter words?
>
> I've got an AM radio that came with an air core antenna.
> (1990's vintage)
> ~4" (10 cm) squarish loop. Not sure how many turns.
> Works fine.
>

** So it's an external loop for a main powered receiver ?

You need to learn how to post unambiguously too.

IOW not smartarse style like Larkin.



.... Phil

[upsid...@downunder.com]

On Thu, 16 Mar 2017 00:17:55 -0700 (PDT), Phil Allison
<palli...@gmail.com> wrote:

>upsid...@downunder.com wrote:
>>
>>
>>
>> The gain ( = directivity x efficiency) for a typical loopstick is
>> very bad in the order of -60 to -80 dB,
>>
>
> ** Compared to what ???

I when the gain is worse than -60 dB, it doesn't matter if the
reference is dBd or dBi, the difference is only 2 dB :-)

>
> A half wave antenna 150 meters long?

The effective hight for a short antenna /in this case strung into the
trees) is only a few dBs below a full size antenna. For derivation,
check John.D. Kraus: "Antennas"

>
>
>> But thanks to the extremely high band noise at LF and MF,
>> you still get usable SNR with such designs.
>
>** This is not right.
>
>Whatever the inherent atmospheric noise at MF, the signal from the transmitter can over-ride it.
>
>AM does not have inherently bad s/n unless you are DXing.

Depending of the definition of DXing , much of the MF/HF stations in
Europe has been shut down. Of course Russian propaganda stations are
still going strong, but wants to listen to them :-).

>I have a hi-fi AM tuner that coupled with small frame antenna ( 40x40 cm) is capable of FM like results from good, local broadcasts.

You must be living very close to the transmitter.

- On SSB the SNR is the same as the RF SNR. To get 10 dB improvement
in the audio SNR, you need 10 times more power-
- For strong (local) signals, this also applies to AM
- For FM transmissions the audio SNR is FM_gain + CNR (carrier to
noise ratio). Above the FM threshold the cost of increasing the SNR
is as costly as on AM
- for digital, going from 48 dB to 96 dB (8 to 16 bits) SNR only
requires doubling the bandwidth and hence transmitter power.

[Phil Allison]

The amdx fool wrote:

>
> Bill Bowden wrote:
>>
> >>> Which is a better design. Suppose you have a 6 inch length of
> PVC pipe with numerous turns of wire that has an inductance of say 200uH.
> Now suppose you use the same (6 inch) piece of PVC with a ferrite rod in the core ...
> >>
> >> There's no comparison.
> >>
> >

> > ** You have **over-snipped** and ruined the OP's question.

> >
> >> That's because the two antenna designs have
> >> completely different impedances,
> >
> > ** The ferrite one will have a higher Q, but similar impedance.
> >
> >
>

> I'll disagree with you on that Phil,

** Where was the over-sniping error?

Did you even think about it?

> I recently built 5 coils
> using 6" polystyrene pipe coupler as a form.

** That would be 6" diameter - right ?

The fuckwit OP was considering 6" *long* pipe that could enclose a ferrite rod.

The rest of you post was OT, tell me how do you get a 6" dia pipe inside a pocket size transistor radio ?

You are an idiot Mikek.


.... Phil

[John Larkin]

On Thu, 16 Mar 2017 15:41:37 -0700 (PDT), Phil Allison
<palli...@gmail.com> wrote:

>John Larkin wrote:
>>
>
>> >> >
>> >> >** The latter is exactly what a ferrite antenna is optimised for.
>> >> >
>> >> >
>> >> In the early days of transistor radios, size was limited and gain was
>> >> expensive, so it was worth some ferrite to get more RF input power.
>> >> Gain is now so cheap that an air core antenna might be OK.
>> >>
>> >
>> >** Really ?
>> >
>> > Try posting an idea that is not full of ambiguities.
>> >
>>
>> Maybe I should have used shorter words?
>>
>
> ** Express you idea clearly

which I did

> or fuck off.

You and what army?

--

John Larkin Highland Technology, Inc

[Phil Allison]

upsid...@downunder.com wrote:
Phil Allison

> >>
> >> The gain ( = directivity x efficiency) for a typical loopstick is
> >> very bad in the order of -60 to -80 dB,
> >>
> >
> > ** Compared to what ???
>
> I when the gain is worse than -60 dB,

** You have not understood the question, by trying too hard to be a smartarse.

> >
> > A half wave antenna 150 meters long?
>
> The effective hight for a short antenna /in this case strung into the
> trees) is only a few dBs below a full size antenna. For derivation,
> check John.D. Kraus: "Antennas"

** Try actually answering the question sometime - dickhead.

> >
> >> But thanks to the extremely high band noise at LF and MF,
> >> you still get usable SNR with such designs.
> >
> >** This is not right.
> >
> >Whatever the inherent atmospheric noise at MF, the signal from the transmitter can over-ride it.
> >
> >AM does not have inherently bad s/n unless you are DXing.
>
> Depending of the definition of DXing ,
>

** FFS - you have the attention span of a gnat.

>
> >I have a hi-fi AM tuner that coupled with small frame antenna
> >( 40x40 cm) is capable of FM like results from good, local broadcasts.
>
> You must be living very close to the transmitter.
>

** No more than the vast majority of people living in Sydney.

( snip more smartase shite)

You are so full of bollocks it smells.



.... Phil

[Phil Allison]

John Larkin wrote:


> >> >> >
> >> >> >** The latter is exactly what a ferrite antenna is optimised for.
> >> >> >
> >> >> >
> >> >> In the early days of transistor radios, size was limited and gain was
> >> >> expensive, so it was worth some ferrite to get more RF input power.
> >> >> Gain is now so cheap that an air core antenna might be OK.
> >> >>
> >> >
> >> >** Really ?
> >> >
> >> > Try posting an idea that is not full of ambiguities.
> >> >
> >>
> >> Maybe I should have used shorter words?
> >>
> >
> > ** Express you idea clearly
>
> which I did

** Another deliberate lie.

> > or fuck off.
>
> You and what army?
>

** Larkin must be either drunk or on drugs today.

Wot an obnoxious, fucking shithead.



..... Phil

[George Herold]

On Thursday, March 16, 2017 at 6:47:58 PM UTC-4, Phil Allison wrote:
> George Herold wrote:
>
> >
> > > >
> > > >> In the early days of transistor radios, size was limited and gain was
> > > >> expensive, so it was worth some ferrite to get more RF input power.
> > > >> Gain is now so cheap that an air core antenna might be OK.
> > > >>
> > > >
> > > >
> > > >** Really ?
> > > >
> > > > Try posting an idea that is not full of ambiguities.
> > > >
> > > >
> > >
> > > >
> > >
> > > Maybe I should have used shorter words?
> >
> > I've got an AM radio that came with an air core antenna.
> > (1990's vintage)
> > ~4" (10 cm) squarish loop. Not sure how many turns.
> > Works fine.
> >
>
> ** So it's an external loop for a main powered receiver ?

Right, It's a JVC "ultra compact component system"
FS-1000

I made a wooden box with handles, so to me it's
semi-mobile. :^)

It's got seven turns of insulated cable,
in a 1 cm width. The coil is not a square, ~10 cm X
12 cm. I could stick it in my back pack and take it to work
(if it mattered) and measure inductance and Q/R on our
SRS box, 100 kHz and lower.

Knowing almost nothing about AM, (and assuming I don't care about price.)
I figure I want the highest Q possible on the front end..
times some area... And I have no idea how to calculate the
"area" of a ferrite. Measurements would be in order.
(Hopefully someone has already done them.)

George H.

>
> You need to learn how to post unambiguously too.
>
> IOW not smartarse style like Larkin.

Larkin is great, I like you too.... :^)

George H.
>
>
>
> .... Phil

[Phil Allison]

George Herold wrote:


> >
> > > I've got an AM radio that came with an air core antenna.
> > > (1990's vintage)
> > > ~4" (10 cm) squarish loop. Not sure how many turns.
> > > Works fine.
> > >
> >
> > ** So it's an external loop for a main powered receiver ?
>>
> Right, It's a JVC "ultra compact component system"
> FS-1000
>

** So why didn't you post that info before?

It's a fucking frame antenna, already discussed here in this thread and been around since the dawn of radio.

>
> Knowing almost nothing about AM, (and assuming I don't care about price.)
> I figure I want the highest Q possible on the front end..
>

** Nope.

You need at least 10kHz of bandwidth at the antenna so the Q must not exceed 50 to 100 across the AM band. You will find that antenna has a fairly low Q in practice.

> > You need to learn how to post unambiguously too.
> >
> > IOW not smartarse style like Larkin.
>
> Larkin is great,

** Larkin is a smug pig and a troll.

He is so narcissistic he thinks he owns the NG and everyone on it.

> I like you too.... :^)

** With friends like you, one has no need of enemies.



.... Phil

[George Herold]

On Thursday, March 16, 2017 at 8:36:16 PM UTC-4, Phil Allison wrote:
> George Herold wrote:
>
>
> > >
> > > > I've got an AM radio that came with an air core antenna.
> > > > (1990's vintage)
> > > > ~4" (10 cm) squarish loop. Not sure how many turns.
> > > > Works fine.
> > > >
> > >
> > > ** So it's an external loop for a main powered receiver ?
> >>
> > Right, It's a JVC "ultra compact component system"
> > FS-1000
> >
>
> ** So why didn't you post that info before?
>

'cos I'm now at home and not at work.

> It's a fucking frame antenna, already discussed here in this thread and been around since the dawn of radio.
>
>
> >
> > Knowing almost nothing about AM, (and assuming I don't care about price.)
> > I figure I want the highest Q possible on the front end..
> >
>
> ** Nope.
>
> You need at least 10kHz of bandwidth at the antenna so the Q must not exceed 50 to 100 across the AM band. You will find that antenna has a fairly low Q in practice.

OK I was thinking of best signal to noise, and figuring that ~1-2 kHz would
be enough.. Everyones "best/ optimal" is a bit different.

>
>
>
> > > You need to learn how to post unambiguously too.
> > >
> > > IOW not smartarse style like Larkin.
> >
> > Larkin is great,
>
> ** Larkin is a smug pig and a troll.
>
> He is so narcissistic he thinks he owns the NG and everyone on it.
>
>
> > I like you too.... :^)
>
> ** With friends like you, one has no need of enemies.

See, that's why I like you.
You treat all with equal disdain, so how could I be insulted.

NG-wise, I'd enjoy more "trolls" like Larkin.

George H.
>
>
>
> .... Phil

[John Larkin]

On Thu, 16 Mar 2017 15:39:52 -0500, amdx <noj...@knology.net> wrote:

>On 3/16/2017 3:06 PM, John Larkin wrote:
>> On Thu, 16 Mar 2017 12:12:14 -0700 (PDT), Bill Beaty
>> <bi...@eskimo.com> wrote:
>>
>>>> Which one would capture the most signal at the AM Broadcast frequencies
>>>
>>> Is your real question , how do we optimize electrically-small 500KHz loop antennas?
>>>
>>> :)
>>>
>>
>> Start by defining optimum.
>>
>>
> He did, as did the op, (capture the most signal)

The most power? That implies a conjugate load, which will kill
selectivity.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[Phil Allison]

George Herold wrote:

>
> > > >
> > > > > I've got an AM radio that came with an air core antenna.
> > > > > (1990's vintage)
> > > > > ~4" (10 cm) squarish loop. Not sure how many turns.
> > > > > Works fine.
> > > > >
> > > >
> > > > ** So it's an external loop for a main powered receiver ?
> > >>
> > > Right, It's a JVC "ultra compact component system"
> > > FS-1000
> > >
> >
> > ** So why didn't you post that info before?
> >
> 'cos I'm now at home and not at work.

** Huh ?? Wot a fucking bullshit excuse.

> >
> > You need at least 10kHz of bandwidth at the antenna so the
> > Q must not exceed 50 to 100 across the AM band. You will find
> > that antenna has a fairly low Q in practice.
>
<
> OK I was thinking of best signal to noise, and figuring that ~1-2 kHz would
> be enough..

** For a 500Hz audio bandwidth ?

You really do know fuck all about AM or anything else.

> >
> > > > You need to learn how to post unambiguously too.
> > > >
> > > > IOW not smartarse style like Larkin.
> > >
> > > Larkin is great,
> >
> > ** Larkin is a smug pig and a troll.
> >
> > He is so narcissistic he thinks he owns the NG and everyone on it.
> >
> >
> > > I like you too.... :^)
> >
> > ** With friends like you, one has no need of enemies.
>
>
> See, that's why I like you.
> You treat all with equal disdain,
>

** That is absurd, I only treat idiots and trolling loonies with distain.

Fraid you fit both categories.

Plus you're a wanker.


..... Phil

[John Larkin]

Hey, if anybody wants Allison, you can gave him cheap. As-is, Free
shipping.

[John Larkin]

On Thu, 16 Mar 2017 18:46:06 -0700 (PDT), George Herold
<ghe...@teachspin.com> wrote:

>On Thursday, March 16, 2017 at 8:36:16 PM UTC-4, Phil Allison wrote:
>> George Herold wrote:
>>
>>
>> > >
>> > > > I've got an AM radio that came with an air core antenna.
>> > > > (1990's vintage)
>> > > > ~4" (10 cm) squarish loop. Not sure how many turns.
>> > > > Works fine.
>> > > >
>> > >
>> > > ** So it's an external loop for a main powered receiver ?
>> >>
>> > Right, It's a JVC "ultra compact component system"
>> > FS-1000
>> >
>>
>> ** So why didn't you post that info before?
>>
>'cos I'm now at home and not at work.
>> It's a fucking frame antenna, already discussed here in this thread and been around since the dawn of radio.
>>
>>
>> >
>> > Knowing almost nothing about AM, (and assuming I don't care about price.)
>> > I figure I want the highest Q possible on the front end..
>> >
>>
>> ** Nope.
>>
>> You need at least 10kHz of bandwidth at the antenna so the Q must not exceed 50 to 100 across the AM band. You will find that antenna has a fairly low Q in practice.
>OK I was thinking of best signal to noise, and figuring that ~1-2 kHz would
>be enough.. Everyones "best/ optimal" is a bit different.

An AM antenna doesn't need to be tuned at all. An untuned coil will
snoop the ambient h-field.

[George Herold]

I guess that's right. As long as most of the noise is "in the air" it doesn't
really matter where the band pass filter is. (Except for dynamic range issues.)

George H.

[Phil Hobbs]

As you say, dynamic range. An untuned input needs a stronger mixer. A
Q of 10 or 20 would help a lot.

On the other hand, one could just use a Mini Circuits mixer with a +17
dBm LO, or a nice analogue mux with square wave drive. It takes a lot
to screw one of those up.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

[DemonicTubes]

That reminds me...anybody else notice DecadentLinuxUserNumeroUno suddenly went silent some time last summer?

[bitrex]

To be fair he probably knows that Usenet was designed to not have a
central administrator...

[dagmarg...@yahoo.com]

On Wednesday, March 15, 2017 at 12:18:38 AM UTC-4, Bill Bowden wrote:
> Which is a better design. Suppose you have a 6 inch length of PVC pipe with
> numerous turns of wire that has an inductance of say 200uH. Now suppose you

> use the same (6 inch) piece of PVC with a ferrite rod in the core with
> considerably fewer turns of wire. Which one would capture the most signal
> at the AM Broadcast frequencies (500K to 2 Megs) and poduce the greatest
> signal output? Would it be more ferrite, or more wire?

There are many variables you're not considering, but maybe this will spark
some ideas.

AIUI, in a uniform magnetic field (such as far from a radio transmitting
source), a loop antenna produces a voltage proportional to the area the
loop encloses. A ferrite rod will increase a loop's effective area by a
factor equal to the effective permeability of the ferrite rod.

So, a 8mm^2 loop wound on a core with an effective permeability of 50
produces the same output voltage as an 400mm^2 loop with no core.

The effective permeability of a ferrite rod, in turn, is mostly a property
of its length-to-diameter ratio.

e.g.,

http://caves.org/section/commelect/mm/mm04.html

Coil geometry also affects a rod's effective permeability. Highest
effective mu is attained by short coils, in the center of the rod.

e.g. Fig. 1,
makearadio.com/tech/files/Ferrite_Rod_Inductance.pdf


Cheers,
James Arthur

[pcdh...@gmail.com]

>That reminds me...anybody else notice DecadentLinuxUserNumeroUno
>suddenly went silent some time last summer?

Yeah, we talked about it a couple of months afterwards, but iirc nobody turned up any leads.

Cheers

Phil Hobbs

[John Larkin]

Resonating an AM antenna needs a giant variable cap, or a varicap and
some sort of tracking voltage source for that. In these days of cheap
gain and signal processing, a mediocre AM receiver (who needs more?)
could well use a simple loop, maybe on the PC board.

Is there anything on AM these days? I haven't tuned into the AM band
in a decade or two.

Amazon has an am/fm radio with earbuds for $6.99.

--

John Larkin Highland Technology, Inc

[John Larkin]

There are moderated NGs. This ain't one.

Most of usenet is dead. SED is unusually active, some of it actually
on topic.

[billbowden]

"John Larkin" <jjlark...@highlandtechnology.com> wrote in message
news:qcdocc5iec6gv362j...@4ax.com...

Rush Limbaugh, Mark Levin, Dennis Prager, Michael Medved, George Noory, Bill
Handel, John and Ken, Tim Conway Jr. and other political hacks. Also there
are financial shows like Ric Edelman, George Chamberlain, Ken Moraif, and
others. Keeps me busy 24/7

[Clifford Heath]

On 18/03/17 06:21, John Larkin wrote:
> Resonating an AM antenna needs a giant variable cap, or a varicap and
> some sort of tracking voltage source for that.

They don't make big enough varicaps for that, but those Superjunction
FETs discussed here recently would work.

A friend designed a specialised hand-held pickup head that had
to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
micro-ohms of dynamic impedance using transformer coupling
(about 8mm square) across a small air gap. The DUT had dozens
of resonances with Q of 1000-5000 across the band.

I suggested using the Superjunction FETs, but the device is finished.

Clifford Heath.

[Clifford Heath]

On 18/03/17 02:38, Phil Hobbs wrote:
> On 03/17/2017 11:28 AM, George Herold wrote:
>> On Friday, March 17, 2017 at 10:30:32 AM UTC-4, John Larkin wrote:
>>> An AM antenna doesn't need to be tuned at all. An untuned coil will
>>> snoop the ambient h-field.
>> I guess that's right. As long as most of the noise is "in the air" it doesn't
>> really matter where the band pass filter is. (Except for dynamic range issues.)
> As you say, dynamic range. An untuned input needs a stronger mixer. A
> Q of 10 or 20 would help a lot.
>
> On the other hand, one could just use a Mini Circuits mixer with a +17
> dBm LO, or a nice analogue mux with square wave drive. It takes a lot
> to screw one of those up.

The SA612 gives you oscillator and 14dB gain mixer in an 8-pin package,
for a buck. Good to 200MHz LO.

[John Larkin]

You can get varicaps up to about 100 pF. To resonate in the AM band,
having a ferrite core would help get enough inductance.

[dagmarg...@yahoo.com]

A perfect application for Y5V / Z5U / X5R ceramic caps. 2uF varicap? Can do!

Cheers,
James Arthur

[John Larkin]

On Fri, 17 Mar 2017 17:13:05 -0700 (PDT), dagmarg...@yahoo.com
wrote:

Good point.

Somebody makes a thing like a varicap, for tuning, but it's actually a
ceramic dielectric thing.

I was always impressed by the tapered curvey variable multi-plate caps
in old radios, how they got the antenna tuning and LO to track. They
did that without computers!

My 600 MHz oscillator needs +-125 fF pF capacitance range to tune. I'm
using a Skyworks dual back-to-back varicap, one side grounded, the
other on the resonator, the tune voltage in the middle.

[George Herold]

Hah, I made an AM radio just that way. Not with a loop, but just
a length of wire. (It's probably the worlds's worst AM radio.)
I had to add series L's (selected for range) to make it work.
Circuit from Terman's radio electronics book.

So a loop (with parallel C) into a TIA? ... (I'd rather use an opamp.)
or will that wig out at the C side of the resonance?

George H.

[dagmarg...@yahoo.com]

On Wednesday, March 15, 2017 at 12:18:38 AM UTC-4, Bill Bowden wrote:
> Which is a better design. Suppose you have a 6 inch length of PVC pipe with
> numerous turns of wire that has an inductance of say 200uH. Now suppose you
> use the same (6 inch) piece of PVC with a ferrite rod in the core with
> considerably fewer turns of wire. Which one would capture the most signal
> at the AM Broadcast frequencies (500K to 2 Megs) and poduce the greatest
> signal output? Would it be more ferrite, or more wire?

The Antenna Ferrite Loopstick Verses
(an exercise in mixed metaphors)
--------------------------------

I raised an aerial into the air,
Pumped in some watts; they landed, but where?
For, so swiftly they flew, the sight
Could not follow the watts in their flight.

But now we all know
(thanks to Edward J. Snowden)
They were scooped from the ether
By one William ('Bill') Bowden.

Whose giant loop, all loaded with ferrite
Had grabbed all my flux (that ain't fair, right?)
To warm up his home, and light LEDS,
And listen to Rush whenever he pleased.

[George Herold]

Oh boy! Can't wait... how do you feed the drive in?
I've always pictured two caps driven in the middle.

George H.

[John Larkin]

On Fri, 17 Mar 2017 17:31:46 -0700 (PDT), George Herold

A short wire antenna gets a voltage equal to the local e-field. All
you need to do is drive an amp with reasonably low input capacitance,
like a jfet or something.

I could patent that, but it's been done for 100 years or so.

--

John Larkin Highland Technology, Inc

[dagmarg...@yahoo.com]

On Friday, March 17, 2017 at 8:36:33 PM UTC-4, George Herold wrote:
> On Friday, March 17, 2017 at 8:13:13 PM UTC-4, dagmarg...@yahoo.com wrote:
> > On Friday, March 17, 2017 at 7:33:04 PM UTC-4, Clifford Heath wrote:
> > > On 18/03/17 06:21, John Larkin wrote:
> > > > Resonating an AM antenna needs a giant variable cap, or a varicap and
> > > > some sort of tracking voltage source for that.
> > >
> > > They don't make big enough varicaps for that, but those Superjunction
> > > FETs discussed here recently would work.
> > >
> > > A friend designed a specialised hand-held pickup head that had
> > > to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
> > > micro-ohms of dynamic impedance using transformer coupling
> > > (about 8mm square) across a small air gap. The DUT had dozens
> > > of resonances with Q of 1000-5000 across the band.
> > >
> > > I suggested using the Superjunction FETs, but the device is finished.
> > >
> > > Clifford Heath.
> >
> > A perfect application for Y5V / Z5U / X5R ceramic caps. 2uF varicap? Can do!
> >
>

> Oh boy! Can't wait... how do you feed the drive in?
> I've always pictured two caps driven in the middle.

That's typical. Varicaps are usually used back-to-back, or with a d.c.
blocking cap.

Cheers,
James Arthur

[George Herold]

Oh no my mistake, I was thinking of how to couple in from a loop.

George H.

[George Herold]

Right, I'm only a tadpole, circuit-wise.
George H.

[rickman]

On 3/17/2017 8:10 PM, John Larkin wrote:
> On Sat, 18 Mar 2017 10:32:58 +1100, Clifford Heath
> <no....@please.net> wrote:
>
>> On 18/03/17 06:21, John Larkin wrote:
>>> Resonating an AM antenna needs a giant variable cap, or a varicap and
>>> some sort of tracking voltage source for that.
>>
>> They don't make big enough varicaps for that, but those Superjunction
>> FETs discussed here recently would work.
>>
>> A friend designed a specialised hand-held pickup head that had
>> to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
>> micro-ohms of dynamic impedance using transformer coupling
>> (about 8mm square) across a small air gap. The DUT had dozens
>> of resonances with Q of 1000-5000 across the band.
>>
>> I suggested using the Superjunction FETs, but the device is finished.
>>
>> Clifford Heath.
>
> You can get varicaps up to about 100 pF. To resonate in the AM band,
> having a ferrite core would help get enough inductance.

Try 500+ pF. They make varactors specifically to tune AM radios. I
just ordered a few.

--

Rick C

[billbowden]

<dagmarg...@yahoo.com> wrote in message
news:b0c5a1f7-85e1-41ae...@googlegroups.com...

Actually, when I was overseas in the south pacific working at a telegraph
station, we put up a long wire antenna tuned to the local AM broadcast
station and managed to light a neon bulb (NE-51) or whatever. I probabaly
could have charged a battery with the thing by just stealing the RF power
from the air. I think it was a 10KW station about a mile away.


.

[upsid...@downunder.com]

On Sat, 18 Mar 2017 10:32:58 +1100, Clifford Heath
<no....@please.net> wrote:

>On 18/03/17 06:21, John Larkin wrote:
>> Resonating an AM antenna needs a giant variable cap, or a varicap and
>> some sort of tracking voltage source for that.
>
>They don't make big enough varicaps for that, but those Superjunction
>FETs discussed here recently would work.
>
>A friend designed a specialised hand-held pickup head that had
>to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
>micro-ohms of dynamic impedance using transformer coupling
>(about 8mm square) across a small air gap. The DUT had dozens
>of resonances with Q of 1000-5000 across the band.

The 1-5 MHz tuning range with a single inductor would need a 25:1
_total_ capacitive range. Since there are stray capacitances, the
actual tuning range for the varactor itself would be even greater.

Thus, you might have to switch the inductance even once in that 1-5
MHz range.

One problem with varactors is that the maximum capacitance occurs at
very low reverse voltages, in some cases in the same order of
magnitude as the RF, causing detuning. Two varactors connected against
each other helps with this.

[Tim Williams]

"Clifford Heath" <no....@please.net> wrote in message
news:58cc722c$0$51765$c3e8da3$f626...@news.astraweb.com...

> A friend designed a specialised hand-held pickup head that had
> to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
> micro-ohms of dynamic impedance using transformer coupling
> (about 8mm square) across a small air gap. The DUT had dozens
> of resonances with Q of 1000-5000 across the band.

Sounds like a horrible case of poorly matched transformer design.
(Unusually badly matched: Q's in the thousands imply impedance off by at
least as much!)

Impossible to say for sure without a winding stackup, though. *shrug*

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com

[Tauno Voipio]

The outer rotor plates of the ganged variable caps were slotted, so
it was possible to fine-tune the tracking, but it was pretty tedious.

--

-TV

[Allan Herriman]

I used to have a Yamaha CT-7000 FM tuner, perhaps one of the best FM
tuners from the 1970s.

From http://www.fmtunerinfo.com/yamaha.html :

"The CT-7000 has a 7-gang tuning capacitor (two gangs in front of the
first MOSFET RF amp, two in front of the second MOSFET RF amp, two in
front of the MOSFET mixer and one for the bipolar local oscillator)."

Alignment must have been fun.

Allan

[John Larkin]

And second harmonic distortion. I'm seeing the same issue in a
photodiode now. The customer wants my amp to have -80 dB THD, but his
photodiode has -40 from varicap effect.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[mkol...@gmail.com]

So the next topic is to compare and contrast the merits
of an H field sensing loop antenna vs an E Field sensing
whip antenna for use on the AM broadcast band.
In practice, most car radios use an E Field whip
and most other radios use an H field loop.
How do they compare?
M

[John Larkin]

Wild guess: indoors, there is a lot of e-field noise. Outdoors, not so
much.

[kevin93]

An H field antenna is directional - the signal would fade whenever you went round a corner. The H field antenna has to be horizontal to pickup the field.

kevin

[bitrex]

Probably for the best; thinking back about the mid 1990s and looking
through the list of dead "alt" newsgroups you wonder "what the hell were
they thinking?"

Not sure anyone is missing the loss of alt.sex.animals.monica-lewinsky
or alt.flame.jews in Web 2.0 2k17

[pcdh...@gmail.com]

>>On the other hand, one could just use a Mini Circuits mixer with a +17
>> dBm LO, or a nice analogue mux with square wave drive.  It takes a lot
>> to screw one of those up.

>The SA612 gives you oscillator and 14dB gain mixer in an 8-pin package,
>for a buck. Good to 200MHz LO.

I've used them in instruments but never in receivers. Gilbert cells are _not_ strong mixers--they have many fine qualities, but good IMD performance is not one of them.

Cheers

Phil Hobbs

[upsid...@downunder.com]

On Sat, 18 Mar 2017 12:57:19 -0700, John Larkin
<jjla...@highlandtechnology.com> wrote:

>On Sat, 18 Mar 2017 12:49:48 -0700 (PDT), mkol...@gmail.com wrote:
>
>>So the next topic is to compare and contrast the merits
>>of an H field sensing loop antenna vs an E Field sensing
>>whip antenna for use on the AM broadcast band.
>>In practice, most car radios use an E Field whip
>>and most other radios use an H field loop.
>>How do they compare?
>>M
>
>Wild guess: indoors, there is a lot of e-field noise. Outdoors, not so
>much.

In the far field (radio station), both the E and H fields are
inversely proportional to the distance (and hence power density
proportional to the inverse square of distance). In this area the free
space impedance (relation between E and H) is 120 pi or 377 ohms.

In the near field (local noise), the H-field drops faster than the
E-field with distance, thus a better SNR can be obtained with
H-antenna in the near field of a noise source.

One can argue where is the border line between near and far field, but
at least 0.1 wavelenghts is definitively near field, i.e for 1 MHz at
30 m. In a residential area, there are a lot of noise sources within
that range. In a car on a highway, there are only a few noise sources
constantly within that distance, as long as you have suppressed any
noise sources from your own car.

[pcdh...@gmail.com]

>Try 500+ pF.  They make varactors specifically to tune AM radios.  I
>just ordered a few.

Current production? Who makes them?

Cheers

Phil Hobbs

[upsid...@downunder.com]

Completely agree.

I had a VLF/LF/MF upconverter using such chips. With a random wire in
the apple trees as antenna directly connected to the mixer, the
usability was bad due to a broadcast station at 30 km distance.

With a tunable preselector, all those problems went away and the
preselector presented a better match between the highly capacitive
antenna and the mixer input. I could hear time stations with good SNR
at 2000 km distance even during the day, while "atomic" clocks could
synchronize only during the short night hours using the internal
ferrite antenna.

[k...@notreal.com]

I've always used the definition of near/far as whether the source can
be resolved or whether it's a point source. IOW, if the source has a
"visible" area, it's near field.

[rickman]

http://www.nteinc.com/diodes/varactors.php?a=12

http://dilp.netcomponents.com/cgi-bin/nteinc.asp?partnumber1=NTE618

--

Rick C

[Jeff Liebermann]

Siemens BB112
<http://pdf1.alldatasheet.com/datasheet-pdf/view/44230/SIEMENS/BB112/+3_342UOGDL.OudGhtNz+/datasheet.pdf>

Toshiba 1SV149
<http://pdf1.alldatasheet.com/datasheet-pdf/view/29858/TOSHIBA/1SV149/+QJJ59UPLRhpDDdAXbNwH+/datasheet.pdf>

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Clifford Heath]

Bit difficult to use FET switching with those to make a 25:1
capacitance ratio however.

It seems that my friend could have used 10x switched capacitors
and just a few varactors for fine tuning, but I never saw the
design parameters. Even the Litz wire pickup coil took a large
design effort.

[Clifford Heath]

On 18/03/17 20:08, Tim Williams wrote:
> "Clifford Heath" <no....@please.net> wrote in message
> news:58cc722c$0$51765$c3e8da3$f626...@news.astraweb.com...
>> A friend designed a specialised hand-held pickup head that had
>> to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
>> micro-ohms of dynamic impedance using transformer coupling
>> (about 8mm square) across a small air gap. The DUT had dozens
>> of resonances with Q of 1000-5000 across the band.
>
> Sounds like a horrible case of poorly matched transformer design.
> (Unusually badly matched: Q's in the thousands imply impedance off by at
> least as much!)
>
> Impossible to say for sure without a winding stackup, though. *shrug*

No. The resonators were micromachined aluminium bars, 52 in series,
tuned a third of a semitone apart, vacuum sealed inside a 1mm^3
chip, and had to be pinged and read at LN2 temperatures. At room
temp, the Q's exceeded 1000; at LN2, some would pass 5000. Fun stuff.

[pcdh...@gmail.com]

>Siemens BB112
><http://pdf1.alldatasheet.com/datasheet-pdf/view/44230/SIEMENS/BB112/+3_342UOGDL.OudGhtNz+/datasheet.pdf>

>Toshiba 1SV149
><http://pdf1.alldatasheet.com/datasheet-pdf/view/29858/TOSHIBA/1SV149/+QJJ59UPLRhpDDdAXbNwH+/datasheet.pdf>

Yeah, I know they used to exist. I still have some MVAM109s in my drawer. I was asking about current production though.

Cheers

Phil "BB209 fan" Hobbs

[Clifford Heath]

Interesting. Please educate me - when you say "strong" do you mean
"involving sharp switching"? Is is Miller effect and LO feedthrough
that limits the "strength"? Does HFA3101 not qualify as "strong"?
Does "strong" depend on the frequency capability of the mixer
compared to the frequency of interest? What topology is used for
stronger mixers?

Clifford Heath.

[pcdh...@gmail.com]

>> I've used them in instruments but never in receivers. Gilbert cells are _not_ strong mixers
>>--they have many fine qualities, but good IMD performance is not one of
them.

>Interesting. Please educate me - when you say "strong" do you mean
>"involving sharp switching"? Is is Miller effect and LO feedthrough
>that limits the "strength"? Does HFA3101 not qualify as "strong"?

A strong mixer is one with really good IMD performance. Antennas pick up everything at some level, so the amount of stuff that your poor little RX front end has to cope with is pretty appalling.

A diode bridge with 2 or 3 series-connected Schottky diodes in each arm and a +17 dBm LO is one decent approach, and you can get one from Mini Circuits in one day if you like.

A bridge made from a fast CMOS mux is another good approach, though it takes more manual work.

These techniques use square wave switching (or nearly), which greatly reduces the proportion of the time when the switching devices are in their 'linear' range.

In order to make an order-1 change in the behaviour of a Level 17 mixer or a FET MUX, an interfering signal has to be pretty big, i.e. a volt or two.

To do the same to a Gilbert cell requires about e/kT, i.e. ~26 mV. So on a simplistic analysis, a Gilbert cell becomes nonlinear at levels a good 40 dB lower than a strong mixer.

Cheers

Phil Hobbs

[rickman]

On 3/18/2017 9:27 PM, Clifford Heath wrote:
> On 18/03/17 13:31, rickman wrote:
>> On 3/17/2017 8:10 PM, John Larkin wrote:
>>> On Sat, 18 Mar 2017 10:32:58 +1100, Clifford Heath
>>> <no....@please.net> wrote:
>>>
>>>> On 18/03/17 06:21, John Larkin wrote:
>>>>> Resonating an AM antenna needs a giant variable cap, or a varicap and
>>>>> some sort of tracking voltage source for that.
>>>>
>>>> They don't make big enough varicaps for that, but those Superjunction
>>>> FETs discussed here recently would work.
>>>>
>>>> A friend designed a specialised hand-held pickup head that had
>>>> to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
>>>> micro-ohms of dynamic impedance using transformer coupling
>>>> (about 8mm square) across a small air gap. The DUT had dozens
>>>> of resonances with Q of 1000-5000 across the band.
>>>>
>>>> I suggested using the Superjunction FETs, but the device is finished.
>>>>
>>>> Clifford Heath.
>>>
>>> You can get varicaps up to about 100 pF. To resonate in the AM band,
>>> having a ferrite core would help get enough inductance.
>>
>> Try 500+ pF. They make varactors specifically to tune AM radios. I
>> just ordered a few.
>
> Bit difficult to use FET switching with those to make a 25:1
> capacitance ratio however.

Not sure what you are saying. 25:1 capacitance ratio is hard to get
with *any* means. I suppose you could literally switch caps in and out.
Why can't you do that with the varactors?

> It seems that my friend could have used 10x switched capacitors
> and just a few varactors for fine tuning, but I never saw the
> design parameters. Even the Litz wire pickup coil took a large
> design effort.

How did small varactors do any better? Were they switched in and out?

Actually, looking at the data sheets for some of these devices they spec
a capacitance range more than 15:1 over less than the full range.
I think you could either work with a wider voltage range (within the max
spec of course) or switch a single fixed cap in and out. Does the
tuning need to be continuous?

--

Rick C

[Clifford Heath]

Thank you. I didn't realize they used series Schottky strings.

Could the need be somewhat averted with back bias instead?

[amdx]

On 3/16/2017 9:57 PM, John Larkin wrote:
> On Thu, 16 Mar 2017 15:39:52 -0500, amdx <noj...@knology.net> wrote:
>
>> On 3/16/2017 3:06 PM, John Larkin wrote:

>>> On Thu, 16 Mar 2017 12:12:14 -0700 (PDT), Bill Beaty
>>> <bi...@eskimo.com> wrote:
>>>
>>>>> Which one would capture the most signal at the AM Broadcast frequencies
>>>>

>>>> Is your real question , how do we optimize electrically-small 500KHz loop antennas?
>>>>
>>>> :)
>>>>
>>>
>>> Start by defining optimum.
>>>
>>>
>> He did, as did the op, (capture the most signal)
>
> The most power? That implies a conjugate load, which will kill
> selectivity.
>
>
OK, I did the experiment.
EDIT; I reread the OPs post, he didn't say 6" dia he said 6" length,

so, my experiment was a bit of a waste and doesn't answer his question.

But here's the info from my experiment.

First, I don't know if the OP was tuning or not, I could not measure
any signal without tuning. So, I tuned.

Two 6.75" diameter coils using 660/46 litz, both approximately close
wound on a styrene pipe coupler.
Coils tuned with a high quality cap and a 20pf fine tune trim cap.
The air core coil has 33 turns and measures 236uh
The core with ferrite has 30 turns and 232uh. without the rod, the coil
measures 195uh. The rod is 3/8" diameter x 8" long. Not a large
inductance change to put a small ferrite rod in a large air core coil.
To center the rod in the coil, I cut two, 1/2' styrofoam circles to fit
the inside of the coupler and put a hole in the center for the rod.
To measure the signal I have high input impedance amp with a gain of 1.
I used the amp to drive a scope (ch 2) set at 50mV/div. I took the
channel 2 output from the back of the scope to drive a Boonton 92BD RF
millivolt meter. I used the scope to compare the visual to audio from a
portable radio to know where I was tuned.
I have three local stations 590kHz, 1290kHz, and 1430kHz.
I did two separate tests, but they were so close it didn't matter.
Modulation made the signal vary, but the Boonton has an analog meter to
help peak the signal.
I did try a second larger diameter poorer quality rod 1/2" diameter
x 7.25 long. It may have out did the air core on the low end with a
few more turns to bring the inductance up to match the others, but it
failed on the upper end.


Best Ferrite Poorer ferrite
236uh 232uh 216uh
33 turn 30 turn 30 turn
Air core coil Ferrite Coil Ferrite Coil

590kHz 59 mv 43 mv 59 mv

1290kHz 15.5 mv 6.7 mv 7.1 mv

1430kHz 10.5 mv 4.2mv 3.2 mv

Mikek





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[amdx]

On 3/14/2017 11:18 PM, billbowden wrote:
> Which is a better design. Suppose you have a 6 inch length of PVC pipe with
> numerous turns of wire that has an inductance of say 200uH. Now suppose you
> use the same (6 inch) piece of PVC with a ferrite rod in the core with
> considerably fewer turns of wire. Which one would capture the most signal

> at the AM Broadcast frequencies (500K to 2 Megs) and produce the greatest

> signal output? Would it be more ferrite, or more wire?
>

I'll run the experiment.

Do you want it tuned?

If not, I have no way to measure the signals of my local stations.
I need the resonance peaking to see the signal.

What diameter PVC?

I have 1/2" OD polystyrene that will allow a little closer coupling
between the ferrite and the wire. 400 turns #28 = 203uh air core.

I have 1/2" CPVC. actual OD. 0.615"
290 turns #28 = 200uh air core


I have 1/2 PVC, actual OD. 0.832. 175 turns #28 = 205uh air core.

Pick one.

I'll also wind one with less turns and use my best Q rod that is 8" long
x 0.375" diameter.

I will check three frequencies, 590Khz, 1290kHz and 1430Khz.

I made a post last night of the wrong experiment (6"dia not 6" long)
It has not shown up this morning, so I'll repeat my measurement method.

To measure the signal I have a very high input impedance amp with a
gain of 1.
I use the amp to drive a scope (ch 2) set at 50mV/div. I took the

channel 2 output from the back of the scope to drive a Boonton 92BD RF

millivolt meter. I use the scope to compare the visual to audio from a
portable radio to know where I am tuned.
Modulation causes a bit of amplitude bounce, but I do a visual average.

Let me know what you want.