A friend of mine is working on a 2 x 8877 amplifier that
he has setup to work on 20, 15, 10, and 6 meters. So far
its working great on 20 thru 10, but he seems to be falling
the victim of stray C at 50 MHz. His PI network design (Q=10)
calls for 32 pf of tune-C, whereas he is measuring ~22pf of
stray for each tube. Eimac specs for the 8877 suggest the plate
C for each tube should be around 10pf plus whatever additional
C is added by the layout, so his numbers, although perhaps
a little on the high side, look like they are at least in the
ball park.
Can a design like this be made to work on 6 meters without
gutting the 20 - 10 meter capability, or is this an unsolvable
problem. What about running with a higher Q (this would allow
for a larger tune C)? Any suggestions?
Thanks,
Mike W4EF...............................
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