[TowerTalk] measuring impedances with a VNA

[Grant Saviers]

I think K9YC has a lot to say about measuring in his HF choke guidance. 
Great work!

If I understand the question correctly here is what I found.

My interest is expanding into VHF/UHF and I began a search for 
literature re chokes for yagis 6m > 70cm.  Not much turned up with 
googling the topic, but I did find an excellent set of articles about 
how to measure beads & clamp ons above HF to 1GHz.  The short version - 
it's HARD.  The good news, my marvelous VNWA can do a great job if the 
issues are understood and the test fixtures built.  However, making 
ferrite, from experience in a prior life making core memories, is more 
art than science and properties are highly variable as Jim noted in his 
test plan.

So, for some great insight IMO re the issues in general about measuring 
ferrite chokes see the 3 articles at
http://www.reeve.com/Documents/Articles%20Papers/Ferrite%20Beads/

I found the answers I needed, but will return to these papers for more 
enlightenment.

Grant KZ1W

On 7/30/2019 4:32 PM, Edward Mccann via TowerTalk wrote:
> How about advice on measuring impedance offered to common mode current in coax with a one-port and two port VNA?
> 
> Ed McCann
> AG6CX
> 
> Sent from my iPhone
> 
>> On Jul 30, 2019, at 3:56 PM, jimlux <jimlux at earthlink.net> wrote:
>>
>> We've discussed the measuring of things like antenna traps, and we've had varying levels of success.
>>
>>
>> https://www.mwrf.com/test-measurement/make-accurate-impedance-measurements-using-vna
>>
>> Discusses three different configurations (one port, and a couple two port measurements), gives the math, and looks at the uncertainties.. each works best in a particular range of impedances.
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