I have a RF choke in a TS-530S that I'm trying to test for induction and frequency. I saw the methodology of building a loop to go around a coil to read this. I really don't want to remove the choke, it's old and fragile. I made a partial loop, see image, and was able to get a frequency from it. I don't know anything about this, it was an experiment. Does anyone have a more educated idea about the test?

As usual, I'll reply with a bunch of questions which will enable us to
guide you.

1) What is your intended frequency range?

2) How about a picture of the choke as well?

3) The picture of your inductor offers quite a bit of coupling potential.
Generally only a hairpin or 1 to 2 turn inductor is held close to the choke
under investigation.

4) Realize in-circuit measurements are biased by directly surrounding and
connected components. Can you lift only one end of the choke for
measurement?

5) Could you please attach the image of the sweep from your VNA of the
choke measurement?

Dave - WØLEV

On Fri, Nov 15, 2024 at 3:31 PM Bob Brown via groups.io <kd2yug=
gmail.com@groups.io> wrote:

I have a RF choke in a TS-530S that I'm trying to test for induction and
frequency. I saw the methodology of building a loop to go around a coil to
read this. I really don't want to remove the choke, it's old and fragile.
I made a partial loop, see image, and was able to get a frequency from it.
I don't know anything about this, it was an experiment. Does anyone have a
more educated idea about the test?

--

*Dave - WØLEV*


--
Dave - WØLEV

Why do you want to measure that choke?
Is there a problem with it?
If you can't loosen that choke, measuring with a VNA is almost impossible because of the correct connection to be made and the own impedance of the VNA, which you have to take into account.
A photo of the choke would already say a lot.

Herman ON1BES

Another idea: with a simple program like RFSim99 you take try the dimensions of the coil and enter them in the program.
You will then get a calculated frequency and an inductance.

Herman ON1BES

Here are the details of my problem.
First, I'm an appliance with a ticket, I ham crammed and got my tech and general license. I am not an engineer, I'm a kit builder. I can put things together but only have a basic understanding. When I need help/information - Google is my go to. I'm learning as I go.
The choke is for a TS-530s. It's the rf choke in the final stage.
The problem that started it all was a blown bypass capacitor on one of the high voltage caps.
Terry Wagner K9TW suggested a look at the RF cage. I measured the inductance of the choke at 98.7uH using my LCR meter. Terry said it should be 160uH.
I am trying to figure out the resonate frequency of the choke and the inductance.
Total length of the ceramic is 70mm.
Width is 12.66mm.
It's 34 gauge magnet wire.
205 turns, I didn't count them they measure up as they should.
Total length of winding is 37.3mm/1/716".
They start 3/4" from the bottom and end 1/2" from the top
While monkeying with the measurements I managed to disconnect both the top and bottom wires - that's why I didn't want to remove it - I finally did and reattached the wires with solder.
What I am hoping to do is determine the resonate frequency and inductance with my nanovna. I've used it for it for measuring baluns and swr but am looking for good directions to figure it out.

Hello

Now that your coil is disconnected from the rest I think you can do "as I do".

You solder only one of the terminals of your coil on the output of the NanoVNA, leaving the coil, and especially the other end, in the air. Possibly place it on a large expanded polystyrene shim.

On the Nano VNA, in Z, you will see very clearly a peak on the resonance frequency of this coil. I do like that too with my traps.
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F1AMM
François

Is this what you meant?

Is this what you meant?

** Yes, the peak on the left. We would have to expand the frequency scale. Do the calculation with the value of the coil and you will find the parasitic capacitance of your coil.

In general, for this type of coil, we make several groups of contiguous turns of different lengths. Suddenly, there would be several resonances
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F1AMM
François

-----Message d'origine-----

De la part de Bob Brown via
Envoyé : dimanche 17 novembre 2024 16:41

http://ham-radio.com/k6sti/coil.htm

Brian

With your setup pictured in your image the second of the hardware you have
no return connection for the VNA other than through the nearfield of the
choke. A better setup which can also be used for measuring resonance of
traps and other resonant circuits is diagrammed in the attachment.

Dave - WØLEV

On Sun, Nov 17, 2024 at 3:53 PM Brian Beezley via groups.io <k6sti=
att.net@groups.io> wrote:

http://ham-radio.com/k6sti/coil.htm

Brian

--

*Dave - WØLEV*


--
Dave - WØLEV

Measure the loop in the diagrammed configuration in both an open (as
illustrated) and a shorted configuration to expose both series and parallel
resonances. ALL resonances should be outside the ham bands if you want to
avoid problems with the final.

Dave - WØLEV

On Sun, Nov 17, 2024 at 6:41 PM W0LEV via groups.io <davearea51a=
gmail.com@groups.io> wrote:

With your setup pictured in your image the second of the hardware you have
no return connection for the VNA other than through the nearfield of the
choke. A better setup which can also be used for measuring resonance of
traps and other resonant circuits is diagrammed in the attachment.

Dave - WØLEV

On Sun, Nov 17, 2024 at 3:53 PM Brian Beezley via groups.io <k6sti=
att.net@groups.io> wrote:

http://ham-radio.com/k6sti/coil.htm

Brian

--

*Dave - WØLEV*


--
Dave - WØLEV

--

*Dave - WØLEV*


--
Dave - WØLEV

OOOpppss....... I should do a better job of proofing. The following
correction:

Measure the *choke* in the diagrammed configuration in both an open (as
illustrated) and a shorted configuration to expose both series and parallel
resonances. ALL resonances should be outside the ham bands if you want to
avoid problems with the final.

Dave - WØLEV

On Sun, Nov 17, 2024 at 7:34 PM W0LEV via groups.io <davearea51a=
gmail.com@groups.io> wrote:

Measure the loop in the diagrammed configuration in both an open (as
illustrated) and a shorted configuration to expose both series and parallel
resonances. ALL resonances should be outside the ham bands if you want to
avoid problems with the final.

Dave - WØLEV

On Sun, Nov 17, 2024 at 6:41 PM W0LEV via groups.io <davearea51a=
gmail.com@groups.io> wrote:

With your setup pictured in your image the second of the hardware you

have

no return connection for the VNA other than through the nearfield of the
choke. A better setup which can also be used for measuring resonance of
traps and other resonant circuits is diagrammed in the attachment.

Dave - WØLEV

On Sun, Nov 17, 2024 at 3:53 PM Brian Beezley via groups.io <k6sti=
att.net@groups.io> wrote:

http://ham-radio.com/k6sti/coil.htm

Brian

--

*Dave - WØLEV*


--
Dave - WØLEV

--

*Dave - WØLEV*


--
Dave - WØLEV

--

*Dave - WØLEV*


--
Dave - WØLEV

A Choke is not more than an inductor. It should be measured as any other one.

Yes, both open and shorted to expose both series and parallel resonances.
If series resonant in the ham bands, lightning can happen in the PA
compartment.

Dave - WØLEV

On Sun, Nov 17, 2024 at 7:47 PM Patricio A. Greco via groups.io
<patricio_greco@...> wrote:

A Choke is not more than an inductor. It should be measured as any other
one.

On 17 Nov 2024, at 16:37, W0LEV via groups.io <davearea51a=

gmail.com@groups.io> wrote:

OOOpppss....... I should do a better job of proofing. The following
correction:

Measure the *choke* in the diagrammed configuration in both an open (as
illustrated) and a shorted configuration to expose both series and

parallel

resonances. ALL resonances should be outside the ham bands if you want

to

avoid problems with the final.

Dave - WØLEV

On Sun, Nov 17, 2024 at 7:34 PM W0LEV via groups.io <davearea51a=
gmail.com@groups.io> wrote:

Measure the loop in the diagrammed configuration in both an open (as
illustrated) and a shorted configuration to expose both series and

parallel

resonances. ALL resonances should be outside the ham bands if you want

to

avoid problems with the final.

Dave - WØLEV

On Sun, Nov 17, 2024 at 6:41 PM W0LEV via groups.io <davearea51a=
gmail.com@groups.io> wrote:

With your setup pictured in your image the second of the hardware you

have

no return connection for the VNA other than through the nearfield of

the

choke. A better setup which can also be used for measuring resonance

of

traps and other resonant circuits is diagrammed in the attachment.

Dave - WØLEV

On Sun, Nov 17, 2024 at 3:53 PM Brian Beezley via groups.io <k6sti=
att.net@groups.io> wrote:

http://ham-radio.com/k6sti/coil.htm

Brian

--

*Dave - WØLEV*


--
Dave - WØLEV

--

*Dave - WØLEV*


--
Dave - WØLEV

--

*Dave - WØLEV*


--
Dave - WØLEV

--

*Dave - WØLEV*


--
Dave - WØLEV

Measure the *choke* in the diagrammed configuration in both an open (as
illustrated) and a shorted configuration to expose both series and parallel
resonances. ALL resonances should be outside the ham bands if you want to
avoid problems with the final.

Parallel resonance and series resonance appear when there are two capacitors, as in a quartz: A large coil in series with a very small capacitor with a fairly large capacitor in parallel.
https://upload.wikimedia.org/wikipedia/commons/b/b7/Quartz_crystal_equivalent.png

I don't see in the diagram where the second capacitor is. I only see the parasitic capacitor in parallel on the inductor.

Do you have an example showing this series resonance?
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F1AMM
François

-----Message d'origine-----

De la part de W0LEV via
Envoyé : dimanche 17 novembre 2024 20:38

On Sun, Nov 17, 2024 at 10:13 PM, François wrote:

I don't see in the diagram where the second capacitor is. I only see the
parasitic capacitor in parallel on the inductor.

The RLC model is an approximation valid only for a coil below parallel self-resonance. Series resonances occur above.

These two papers cover coil self-resonance in detail:

https://www.researchgate.net/publication/353572229_SELF-RESONANCE_IN_AIR_COILS

https://g3ynh.info/zdocs/magnetics/appendix/self_res/self-res.pdf


On Sun, Nov 17, 2024 at 03:53 PM, W0LEV wrote:

Yes, both open and shorted to expose both series and parallel resonances.

Just connect the coil between the two VNA ports. I think both series and parallel resonances should be evident.

Brian

The RLC model is an approximation valid only for a coil below parallel self-resonance. Series
resonances occur above.

** Ah, I hadn't thought of that. Obviously
Thanks for enlightening me and this is the case in the case of Bob's coil

--
F1AMM
François

-----Message d'origine-----

De la part de Brian Beezley
Envoyé : lundi 18 novembre 2024 14:12

Brian:
Is this what you meant to measure the parallel frequency? What chart am I supposed to use to read this?
Is that the same for the initial reading, single solder point - hanging?

This is all on S11

I would be interested in the .s1p measurement file of your coil connected to the S11 output port of the VNA. Connected with:
one wire to the output
and the other wire to ground.

Maybe you don't know how to retrieve this file.
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F1AMM
François