Carl (and I am sending this to the reflector as well),
In our discussions the past couple of days about the supressors that I
have tried in my 4-1000A amplifier, you have pointed out that the reason
I have had problems was that I have used like #18 or #20 magnet wire for
the coil. I had mentioned that if I had more than one turn in the coil,
that I would burn up the supressor resistors. You said that it was
because I was not using good heavy strapping for the coil. Silver plated
was best you said.
What I forgot to mention was that I DID try that method. A source of
parts for me has been a defunct Johnson-Viking Invader that I have. I
pulled one of the supressor coils out of that beast and tried it on my
4-1000A. The coil was 2 turns of silver plated strapping about 1/2"
wide. Coil diameter was about an inch. The resistors were 3 3 watt
carbon resistors with a total resistance around 100 Ohms or so (I
forget). Well, guess what....I burned up every single resistor
combination that I tried in that supressor. I think I even tried
experimenting with different numbers of turns, but that didn't work
either. Additionally, I even tried some 1/8" diameter silver plated,
solid copper tubing that had been an inductor in the Invader. Didn't
work either.
The only thing that worked was one turn of #20 magnet wire.
Now, you probably would like to point out that my resistors were not good
metal oxide resistors or globars. However, 3 3watt resistors in parallel
give a total power handling of 6 watts so that should have been plenty.
According to what you have said, that suppressor should have worked. It
didn't.
Also, even if I would have gotten larger resistors or globars, I bet that
even then they would have gotten very hot on 10 meters and would not have
worked on 6 meters.
I really do not think that wether one uses strapping or #18 or #20 magnet
wire makes any difference. #18 or #20 wire can easily handle the
currents that flow through the coil and so why the need for the
strapping? Sure, the strapping has less parasitic inductance than the
wire, but I think that in a coil at HF, we can pretty much ignore those
parasitics. I would bet that a coil of #18 guage wire has about the same
inductance as a coil of silver plated strapping (same coil diameter &
number of turns). I haven't measured this yet with my dip meter, but I
think it would be an interesting experiment, so I will do that and report
back.
Now, the only reason that I can think of why the silver platted strap
didn't work was too much inductance. Either due to too many turns or too
large a diameter. Again, I went to a single turn of magnet wire and it
worked.
Now, I would like you opinion on why a supressor that was built pretty
close to what you recommend failed to work properly in my amplifier?
BTW, I am leaving the whole concept of nichrome wire, etc. out of this
discussion. I strictly want to focus on why you think that strapping is
so much better than wire.
73,
Jon
KE9NA
-------------------------------------
Jon Ogden
KE9NA
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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