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[AMPS] Supressors on my 4-1000A

To: <amps@contesting.com>
Subject: [AMPS] Supressors on my 4-1000A
From: jono@webspun.com (Jon Ogden)
Date: Sun, 26 Apr 98 22:21:52 -0500
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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