[Amps] SB-220 parasitic suppressors

[K7RDX]

OK...Strange a fellow would order your kit if he couldn`t solder the "Thing"
in place.Jim.
----- Original Message -----
From: "R.Measures" <r at somis.org>
To: "K7RDX" <k7rdx at earthlink.net>
Cc: "Amps reflector" <amps at contesting.com>; "Vic Rosenthal"
<vic at rakefet.com>
Sent: Wednesday, November 03, 2004 10:21 PM
Subject: Re: [Amps] SB-220 parasitic suppressors


>
> On Nov 3, 2004, at 4:02 PM, K7RDX wrote:
>
> > Vic is absolutely correct about resistors changing value due to
> > heat/age/mistuning,etc. Another way to tame especially squirrly amps
> > is to
> > add a supressor to the cathode side in addition to the usual anode
> > ones. I
> > read somthing about that idea several years ago and found it effective
> > in
> > taming my pair of 4-1000`s when running 6700vdc. My hf GS-35b AMP has a
> > supressor only in the cathode and has been super stable for the last
> > four
> > years.....AL-1500 Owners might give that one a try.
>
> A GS-35b has 0.12pF of anode-cathode feedback C.  An 8877 has 0.10pF of
> it, so they have a fairly similar amount of internal feedback.  Our
> 8877 low VHF-Q parasitic suppressor retrofit kit has both an anode
> suppressor and a cathode suppressor.  It comes with a money back
> guarantee.  So far, the only refund has been to a guy who said he did
> not know how to solder.
> --  Today's trivia question:  At its max freq of 1000MHz, what is the
> reactance in ohms of the output/input feedback path in a (g-g) GS-35b?
>
> > Parasitic discussion
> > sure brings out the pros&cons as well as the snake oil guy(s.)......Jim
> > K7RDX
> > ----- Original Message -----
> > From: "Vic Rosenthal" <vic at rakefet.com>
> > To: "Amps reflector" <amps at contesting.com>
> > Sent: Wednesday, November 03, 2004 2:04 PM
> > Subject: [Amps] SB-220 parasitic suppressors
> >
> >
> >> One reason that an SB-220 can develop VHF parasitics is the following:
> > the
> >> original suppressors use 2-watt carbon composition resistors.  These
> > resistors
> >> tend to increase in value when they age, and especially when they are
> > heated.
> >> If an SB-220 has been used heavily, especially on 10 meters or --
> >> worst
> > case --
> >> on 10 (or 11!) meter AM, the resistors will have gotten quite hot and
> >> may
> > have
> >> changed significantly in value, or even opened up.
> >>
> >> If the resistors are discolored, they should definitely be replaced.
> >>
> >> --
> >> 73,
> >> Vic, K2VCO
> >> Fresno CA
> >> http://www.qsl.net/k2vco
> >>
> >> _______________________________________________
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> >
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> >
> >
>
> Richard L. Measures, AG6K, 805.386.3734.  www.somis.org
>
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