Hi Mark,
> It would seem to me that using a swamping resistor
> at the cathode of a cathode driven amp would get
> rid of excessive drive power and also limit the
> maximum swing in the load value the cathode shows
> to the source, but would do nothing to prevent harmonic
> currents from finding they're way back to the source.
Actually swamping does attenuate harmonics. Remember the loss
goes both ways, so if the incoming signal is attenuated by the
resistive load with only a fraction actually driving the tube...the
same would be true of harmonics.
As far as I know the loss or attenuation is not necessarily equal or
truly bilateral. It can be different, but it is certainly there for
harmonics.
I've been very successful, as I'm sure many others have, with using
a swamping resistance on grid driven class AB2 tubes.
Unfortunately with a medium or low mu cathode driven triode, you
won't likely have much drive power to "waste".
> I would also think besides the obvious lack of a path
> for harmonic currents, in order for a swamping resistor to
> allow the amp input to look like a constant load to the
> source the resistor would have to be considerably
> lower in effective "R" than the cathode. And if that
> were the case the swamping resistor would draw
> more power from the source that the amplifier would.
>
> Mark WB8JKR
>
>
> On Fri, 18 Jan 2002 19:26:56 -0500 "carl seyersdahl"
> <carlseye@tampabay.rr.com> writes:
> >
> > In reference to the subject matter. I have an article here written
> > by a ham in spain and published by Svetlana several years ago. This
> > gentleman built an amp, single 572B, using a home made rf choke and
> > input transformer combined, and using a large swamping resistor ,
> > about 75 ohms at 40 watts, untuned input..
> > Just how good it turned out I can't say, but it is an interesting
> > thought
> > on the subject.!! I mention this only in the interest of theoretical
> > discussion.
> > I have a copy of the article if anyone is interested
> > have a good day all.
> > carl / kz5ca
>
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73, Tom W8JI
W8JI@contesting.com
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