> From: Peter Chadwick <Peter.Chadwick@gpsemi.com>
> Subject: [AMPS] suppressors
To: <amps@contesting.com>
> Date: Fri, 12 Sep 97 09:39:15 +0000
> desirable to have a steadily increasing Q with frequency. I will stick
> my neck out and say that although a 'standard' suppressor will often
> work, a better result is likely to be obtained by designing the
> suppressor for the amplifier - not just a suppressor for 572Bs, 811As,
> 3-500Zs or whatever, but taking into account the particular set of
> parasitic impedances in the plate and grid circuits in that amplifier.
> That suggests that changing things like tank tuning capacitors and
> switches when 'copying' someone else's design may lead to different
> parasitic suppressors being needed.
Yet at least one guy who "sells improvement kits" doesn't even look
at the amplifiers he makes kits for, and can't even measure Q above
60 MHz and only below 60 with an very old Boonton meter.
> It might be possible to design the parasitic suppressor from theory,
> using something like Eesof to model the real components and the layout.
> It's almost certainly quicker to use empiric methods.
Actually Peter it's a pretty simple deal to measure the oscillation
frequency (if the PA oscillates) and then sweep the anode system near
that frequency.
If the empirical cut and try (Edisonian) method is used, it's
absolutely necessary to raise HV and vary bias during the tests to be
sure you have really "fixed" the problem.
73, Tom W8JI
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