Dear Alan,
thank you for sharing the measurements. I assume you used NanoVNA-saver.
Can you please share the s1p or s2p files if saved?
TNX, 73 Ady YO2NAA
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On Fri, Dec 27, 2019 at 5:14 AM alan victor <avictor73@...> wrote:
Re visit this topic as I am looking at plate chokes for a tube amplifier.
I used 1010 points from 100 kHz to 30 MHz. There are 3 chokes shown here.
The older National R175 shown in a prior post with its problems of 2 in
band resonant conditions, a 230 uH homebrew choke for 160 - to - 40 meter.
Fine but horrible beyond 15 MHz and finally a fairly nice choke at 100 uH
on a ceramic core complete with a 500 pF/20 kV bypass capacitor. This choke
shows a single resonance but is out of band.
It appears unnecessary to provide a short across the choke to pick up
these loops if a shunt S11 measurement is used. In all cases the parallel
resonate point crosses the open circuit side of the chart. A short across
the choke simply rotates the reflection towards the short circuit side of
the chart however the series loops stay in tact.
Alan
