Phil Clements wrote:
> It is obvious that suppressors on an 8877 amp are optional, depending on the
> design and use requirements.
The handbooks describe procedures for checking if an amplifier is stable at
VHF.
If not, and this of course depends on the layout and components used and the
parasitic tank circuits created thereby, one way to stabilize it is by adding
the usual suppressor to the plate circuit. It's desirable to use the minimum
inductance needed; if you've seen the ones in some Alphas they consist of a
carbon resistor soldered across a copper strip not much longer than the
resistor
itself! It would be even better, from the point of view of efficiency,
reliability and cost, if it could be eliminated entirely.
My point is that it is part of engineering an amplifier -- the layout and
components used (including the tube type) will determine if there is need for a
suppressor and what form it should take. I presume that the designer of the
AL1500 checked the amplifier on all bands and under various conditions and
determined that it was stable without the suppressor.
I'm sure that some amateur and professional designers would put one in, "just
in
case". As an amateur, I would! But it would be better engineering to perform
the appropriate analysis and testing on which to base the decision to include
the suppressor or not.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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