Connect the parallel resonant circuit in line
with their transceiver input and tune for a null or connect it
across the input and tune for a peak. You could also have them
reconfigure it as a series resonant circuit, test it in the same
way and learn why traps are parallel resonant, not series
resonant.
For an unforgettable lifelong lesson, albeit an
expensive one, let them transmit into it. OK, maybe just a
strong warning not to ever do that would be in order.
Eric KE6US
On 12/18/2019 10:51 AM, k6whp wrote:
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Thought I'd
throw this out for the group. I got trapped [sorry!] into
schooling some "Baofeng Techs" (FNGs) who are interested in
getting into HF about building trap antennas. Of course, being
new, they do not have the luxuriant array of test equipment we
seem to stack up over the years so I wanted to suggest to them
ways they could construct traps and prove out the resulting
resonant frequencies of same.
They will be pointed to the appropriate theory, formulas, and
internet calculators to derive the component values, inductance,
number of turns, etc. but after they have built the traps, I
wanted to provide them with a crude but decent method of
determining the resonant frequency. (It would not do, after all,
to have them wind a 20m trap resonant at 16 MHz.)?
Assume they have a brand new transceiver, can afford a decent VSWR
meter, and can lay their hands on stuff like #47 panel lights,
LEDs, wire, coax, etc. and know how to solder. They know ought of
antenna analyzers, don't have a clue what a GDO is, and other
"desert island" stuff like that.
Appreciate any ideas.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got
worse."
