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Re: [Amps] suppressors

To: Steve Thompson <>,
Subject: Re: [Amps] suppressors
From: Bill Fuqua <>
Date: Fri, 13 Jul 2007 09:24:37 -0400
List-post: <>
    Not that it makes much difference but with some tubes the plate to 
ground capacitance is a good portion of the "tune-C" capacitance on 10 
meters, so there is a fair portion of the circulating current flowing thru 
the suppressor. As I said it usually does not make much difference but it 
could complicate the analysis a bit.
    It just occurred to me that RF current does flow thru some "resistance 
wire" in many tubes. But it is tungsten, the filament. However, this should 
not affect the analysis of the suppressors since most of the RF current 
that produces VHF parasitic oscillations flows between the plate and the 
closest grid.
Bill wa4lav

At 12:01 PM 7/12/2007 +0100, Steve Thompson wrote:

>c.s. wrote:
> >          There has been , in the past, much discussion about parasitic
> > suppressors in this list.!! What I'd like to see is a comparison between
> > the "nichrome" and the " copper" wire suppressors , in actual use by
> > actual people!! I've used both and have not seen much difference between
> > the two.!!!  Currently I'm testing both and haven't found much
> > difference in 10 mtr. performance!!!
>You probably won't see much difference on 10m - the suppressor should be
>adding 1-3 ohms in series between the plate and tune C. The circuit
>impedance is typ. 2-4k, so the power loss is a few tenths of a percent.
>To me a measure of 'goodness' of a suppressor is the ratio of series
>resistance it adds between the plate and tune-C at 30MHz and 100MHz.
>I've just spent an idle hour making and measuring a number of
>suppressors to give different values of R at 30MHz, using copper and
>nichrome for the inductor part. In every case so far, copper gives
>better 'goodness'.
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