John Popelish wrote:
wrote:
(snip)
Time delay measurements of current at each terminal of a "bug-catcher
style" loading coil are now at:
http://www.w8ji.com/inductor_current_time_delay.htm

Thank you for posting the test results. But I see no information that
would allow me to reproduce it. What test equipment and what
measurement set-up was used to produce these results?

I used a HP8753C network analyzer with small current transformers
similar to those used in directional couplers.

I calibrated using normal proceedures, and verified calibration by
inserting known transmission lines. For example when I substituted a
very short jumper, time delay was a few picoseconds. When I connected a
10 foot RG-8X jumper, time delay was about 13.5 nS.

For my phase angle measurements I used a dual channel HP vector
voltmeter with a HP generator, and similar current transformers when
measuring current.

I suppose most people would want to use a scope, but it would not be
near the accuracy of a dual channel vector voltmeter or especially a
vector network analyzer.

I have regular test fixture built on blank PC boards, since I do this
stuff every week for work. It does not "fit" a large coil well, so I
had to support the coil on two tall blocks of styrofoam and clip lead
to it.

I do have a large fixture that is a four foot PC board "box" with
various test jacks for connections to probes I use with larger
components, but my bench is to cluttered to fit it right now. In any
event a groundplane several inches away doesn't seem to bother things.
The only thing that moved when I moved the inductor close to the
fixture was the self-resonant frequency came down a few MHz. Time
delays did not change much unless I added an extra foot of clip lead,
then they increased about 1nS.

If it's useful, I guess I could add some more stuff. But probably
nothing extensive until after Dayton.

Since all of my data agrees with data made a few years ago by a
different person using a different method with different equipment, and
since it agrees with reference material I have, I don't see any reason
to treat it like cutting edge results. The physics is pretty solid, and
the measurements agree.

73 Tom