https://www.laskakit.cz/user/related_files/nanovna-user-guide-english-reformat-jan-15-20.pdfСтана ясно, че освен вяра, вярваш избирателно, когато и каквото ти изнася.
Measuring a choke balun (common-mode choke) with a NanoVNA involves determining its common-mode rejection (impedance) by measuring the
(insertion loss) or
(reflection) across the desired frequency range (typically 1–30 MHz). A good choke should provide
attenuation (
), or high impedance on a Smith chart (
) within the operating band.
This video shows how to measure the S21 insertion loss to test if a choke is working:
Related video thumbnail
53s
Budget Ham Radio
YouTube • 27 Dec 2025
Key Measurements
LogMag (Insertion Loss): This is the best method to measure effectiveness. The choke acts as a band-stop filter for common-mode currents.
Setup: Connect Port 1 to the input and Port 2 to the output. Connect the shield to shield on one side, and center pin to the other (testing only one conductor of the bifilar winding).
Goal: A deep dip in
(ideally
to
or lower) in your target band.
(Smith Chart/Impedance):
Setup: Short all inner conductors together, and all outer shields together on both sides. Connect the NanoVNA Port 1 to the input.
Goal: The Trace should show high impedance (far right on the Smith chart) at the operating frequency, indicating a high common-mode reactance.
Steps to Measure
Calibrate: Perform a SOLT (Short, Open, Load, Through) calibration on both ports covering your frequency range (e.g., 1–50 MHz).
Connect DUT: Connect the Choke (Device Under Test) between Port 1 and Port 2 using short, direct connections to minimize stray capacitance.
Analyze: Set the screen to
(LogMag) to observe attenuation, or
(Smith Chart) to see impedance.
Evaluate: A well-designed 1:1 choke should be effective throughout the HF band. If the attenuation is too low, add more turns or a better-suited ferrite mix (e.g., Mix 43).
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Последни публикацииВълновото съпротивление се определя от вътрешния диаметър на оплетката и диаметъра на жилото,диалектричната константа на изолатора има отнощение към коефициента на скъсяване на кабела.Поне така пишеше в дебелите книги навремето когато още не беше на мода дистанционното обучение
