Bill, wrt had mentioned abt using a variable cap in series with a coil, in
series with a resistor, all wired between
cathode and chassis, to eliminate parasitics. I think the idea of the
resistor was to broaden the parasitic freq response.
Ok, between low C and high L..... and at the other extreme, High C.. and Low
L... there is an infinite amount of combo's
that would still resonate on the parasitic freq. Which combo would provide
the widest BW ?? I think it would be the
low C, High L combo.. but not sure ? Has anybody tried this b4 ? On
paper, it looks like it would work.... and no
resistor required. It would amount to a series resonant tuned circuit... and
should suck out the parasitic freq.
I saw a 50 mhz amp in one of the books, where instead of using a doorknob for
a screen bypass cap, they used a
coil and variable cap in series, from screen to chassis. This was supposed to
make for a better RF grnd at 50 mhz, than
the usual doorknob bypass cap. Same idea, different application.
later...... Jim VE7RF
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