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[AMPS] construction of parasitics

To: <>
Subject: [AMPS] construction of parasitics
From: (skipp s isaham)
Date: Thu, 19 Jul 2001 18:30:56 -0700
re: parasitic construction.
Hi Bill,
I also had problems one of the first times I tried to 
construct and install one of Rich's parasitic kits in 
a floor console model Henry.  The resistors got 
really hot and failed. 
The problem also surfaced on a very cranky SB 
220, I was working through from years of neglect. 
So I did the proper math home work to figure out 
the coil inductance values for my suppressors which 
were right in line with Rich's paperwork. My math 
and testing came up with inductance values about 
85 to 95% of the suppressor kit values.
Upon construction of my own model suppressors, 
I noticed that very small changes in the physical 
construction added or subtracted from the inductance 
values.  Indeed, it's very possible to construct two 
almost exact physical size inductors that differ in 
inductance value a dramatic amount.  To much 
inductance is really bad news in a suppressor made 
with low wattage resistors. 
To complete the amplifiers I constructed a batch 
of coils with similar inductance values and ran them 
through my test equipment (HP Network Analyzer 
and a Sencor LC-102) to match up and tweak 
the coils. 
Rich's paper work mentions the resistors do/should 
run warm/hot in operation. Using his values, parts 
and information they do indeed run hot at the high 
end of the HF bands.  The tweak is the guy who 
doesn't have lab test equipment to ensure the 
suppressor inductance value is not a significant 
amount over the desired value, else they have a  
potential to fail in certain longer duty cycle conditions. 
My fix was to actually "upgrade" the suppressor resistance 
value to a higher watt rating and use close measured 
and matched coils, being careful to er on the side of 
slightly less than the desired inductance. 
My results then and to this day have been dramatic, 
not one of the many cranky amplifiers I've reworked 
has shown parasitic probablems since my retrofits. 
That includes my very cranky BTI 3-1000 amplifier 
with a really squirly aged tube.  
Rather than argue over any of this, I'll just throw out 
that I prefer to use higher watt MF resistors than the kit 
supplied values and I pay very careful attention to 
the inductance values.  In my examples, slightly less 
L might not be enough (for the most part it often is), 
and too much L is almost always bad for the resistors 
when things are running full tilt. 
Your results may vary.. my results are still on the air. 
skipp    wv6f      I've added all three of the 
vhf arcos amps and some tube data sheets.
--------- Forwarded message ----------
From: "bill thomas" <>
To: <>
Date: Thu, 19 Jul 2001 13:44:41 -0500
Subject: [AMPS] Re: Parasitics
Message-ID: <>

I once had a Henry 2K-3 in which I installed Mr. Measures' suppressor
I thought I was doing a good thing.  The first time I put it on 15 meters

several of the resistors exploded much as a shotgun shell would do. I 
promptly went back to the Henry factory suppressors and never had another

problem, nor did I have a problem prior to that.  For some stupid reason
was convinced that that bit of nichrome was going to save me from eminent

disaster.  In my 25 years of hamming, never have I experienced a
with my Henry 2K-3 (2x3-500z's), My AL1200 (3cx1200A7), or my Henry 3K 
Classic X (8877).

This suppressor kit thing reminds me of the travelling salesman selling
all elixir out of the back of his wagon.  "Guaranteed to cure your gold 
sputtered meatballs...."

Bill Thomas   k1xt

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