[TowerTalk] CM Choke

[Jim Brown]

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

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