Coil Construction, was: [AMRadio] Fun with 4D32's...

Larry Keith kq4by at
Thu Jan 4 14:04:47 EST 2007

thanks mucho for the info!
I printed it out, and will attempt to make a coil
about 12 to 14 inches long, 4 inches diameter, out 
of about #10 buss wire.

Sounds doable!  I have made them up to 6" diameter and about 15" long  (160M
bugcatcher coil)..

The original design in the ARRL 65 handbook calls
for a 3 inch coil of #14 for 250 watts of AM,
and I can run up to 700 watts of carrier, so
will go with #10 I think and make it 4 inches
in diameter, although I expect a lot of cut and try.

Sounds good for 160 through 20, if I remember the specs in the handbook
about wire size and power..  Good ventilation will help..

The design calls for four coils on one form, the
two inner coils 4 turn links, should I wind the coil
then cut, or try making them separate from the start?
The original design used B+W coil stock with 1/2
a turn unwound for the links...

I think I would make the coil and then cut the wire, as suggested..  Making
a long coil results in more uniform product all the way through.  In my
opinion, short coils are more difficult to deal with..

I may have to make the caps as well, they call for
two dual 100pf caps at 4500 volts, plus a single
250 pf cap at 2000 volts, and I figure I should 
double the voltage ratings.

Random thought:  Ten-Tec makes and sells a variable capacitor kit, 500 pf @
4KV..  Seems like you could modify one, as you build it, to produce the dual
cap. And, modify the other to produce only the 250 pf that you need.  I
wonder if anyone has tried that.  Of course, I would go hunting in the
various hamfests.  That is where I find most of mine.



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