On 12/31/2017 7:30 PM,Jim Brown <jim@audiosystemsgroup.com> said:
"OK. BUT -- it's NOT an inductor. See below. Also study
k9yc.com/RFI-Ham.pdf Or study it in the ARRL Handbook. It was added in
2011. "
I advised a setup for the measurement like that for a simple inductor,
not that a choke IS a simple inductor. Of course, it is a complex
impedance, but the primary effect, isolation, is mainly achieved through
inductive impedance, as the charts in <k9yc.com/RFI-Ham.pdf> clearly
demonstrate. I apologize for not being more clear, but the point of the
exercise is not to measure the complete complex impedance to within 10%,
although you are right that a simple S11 reflection measurement has a
limited impedance range depending on the instrument, but to assess the
suitability for use in a certain frequency range, and the S11
measurement on a Smith chart will clearly demonstrate resonance effects
and the effective frequency range.
I do want to thank you for your comments as it prompted me to do more
research and found a paper which discusses increasing the range of
impedance measurements possible with a VNA using shunt and series S21
measurements. See slides 63-69:
https://www.keysight.com/upload/cmc_upload/All/ChallengesandsolutionsforImpedance.pdf
73,
Avery, WB4RTP
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|