>I,ve recently obtained a number of new surplused 4PR1000A tubes and
>promptly began to put together an amplifier using a pair of these tubes.
>Using 5500v on the plate, I found that they require a fair amount of
>drive. With the power supply as well as the rf deck completed in a
>modualer cofiguration, it is easy to change.
> My question is... Using the same chassis and power supply, what would
>be a better tube configuration. I would still like the amp to remain
>grounded grid.
>
Dave:
A pair of 4PR-1000As can be driven by 100w in Class AB1 grid-driven
linear service. The paralleled grids would be terminated with 200 ohms
and fed through a bifilar (1 to 4) step-up toroidal broadband
transformer. The optimum screen potential is around 1100V. For SSB, I
would choose an anode/plate supply of 6 to 7.5 kV. The screens can be
directly-grounded if the fil. CT/cathode/neg. HV return is floated above
ground. For best stability, and a virtually perfect input SWR, I would
neutralize. Class AB1 neutralization is easier than many g-g amp.
builders presume. For a representative circuit see:
http://www.vcnet.com/measures
Rich---
R. L. Measures, 805-386-3734, AG6K
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