I think I've found a way to measure the resonant frequency of a shorted stub
for the purpose of determining the Velocity Factor of twinlead cable.
Unfortunately it requires the use of an HP3577A Network Analyzer, but I
latched on to a used one a few years ago on Ebay, so I can have all kinds of
fun with it. But there's a question of how to interpret the results.

I use two small one turn Faraday-shielded loops that I made out of RG58 a
while back to induce or detect signals in various circuitry. For the purpose
of this measurement, I loosely couple two of them, one from the analyzer
source and the other to its receiver, about 4" apart with the loops parallel
and axially aligned. Then I introduce the stub midway into the space between
the loops, oriented for a maximum effect and observe a small peak followed
by a small dip in the received spectrum sweep. My question is, which is the
true measurement of the resonance of the stub - - the peak or the dip or the
zero-crossing between them, and why? Up to now, I've felt the dip is the
correct feature to use, since at resonance the stub patently steals a little
energy from the coupled fields, but that doesn't really say why it steals
energy, or why the peak isn't just as valid an indicator.

Thanks for your help,

Chuck, W6PKP