[TowerTalk] CM Choke

[Máximo EA1DDO_HK1H]

Jim, I´ve seen someone else making a S11 measurement for CM choke?

Is that correct?


http://www.lb3hc.net/archives/1358


I always use S21.


Thank you


73, Maximo

________________________________
De: TowerTalk <towertalk-bounces at contesting.com> en nombre de Jim Brown <jim at audiosystemsgroup.com>
Enviado: martes, 10 de octubre de 2017 15:58
Para: towertalk at contesting.com
Asunto: Re: [TowerTalk] CM Choke

On 10/10/2017 7:59 AM, Dave Hachadorian wrote:
> Speaking of "tuning" a choke, couldn't you just run 50 watts into a
> dummy load, and tee off a choke and a 100 ohm resistor to ground, and
> calculate the impedance of the choke by measuring the RF voltage
> across the resistor and the RF voltage across the dummy load?

No, because that's not the common mode circuit. There IS, however, a
method somewhat similar to that which I used for the data I gathered.
It's detailed in this set of slides.

http://k9yc.com/CoaxChokesPPT.pdf
Jim Brown K9YC Santa Cruz, CA http://k9yc<http://k9yc.com/CoaxChokesPPT.pdf>
k9yc.com
Coaxial Transmitting Chokes Jim Brown K9YC Santa Cruz, CA http://k9yc.com



FWIW, I have never gotten good data using any form of reflection-based
measurement system. The problem is that the Z of the choke is much, much
greater than the Z of the measurement system. The error shows up in the
resonant frequency.

73, Jim K9YC

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