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@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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