On Mon, 15 Dec 2008 18:31:50 -0500, Roger W. Macdonald wrote:
>The attached photos show
Many mailing lists, including this one, don't allow attachments.
That's good, because it limits the nasty games than be played. I'd
like to see your photos. Maybe you can post them somewhere with a
link in an email.
Re: your chokes and 160. As noted in my tutorial, a choke is
essentially a low Q (high loss) parallel resonant circuit. A
single turn of #43 resonates up around 200 MHz and is only a few
tens of ohms. As we add turns, the resonance moves down in
frequency and the impedance rises approximately as the square of
the turns.
You probably used enough turns to get the resonance down around 5
MHz, and it's a broad resonance, so it worked down to 80. More
turns would get you down to 160. A better solution is to use #31,
which has an even lower Q resonance. 10-12 turns of that would
probably solve your problem from 160-40, and maybe up to 20. If
you still had problems on the higher HF bands, a second choke
could be added in series.
Sounds like you did some smart troubleshooting, the key points of
which were looking for the wires that might be good antennas at
the frequencies where you were having problems and using what you
had available to kill the current on them. Thanks for sharing your
work.
73,
Jim Brown K9YC
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