> Thanks Tom. The next question is; Does it matter which
> side of the blocking capacitor I attach the termination to
> ground. This is a 50 mHz amp, and to attach to the anodes
> would mean long leads. If I hang the resistor at the input
> to the pi-network, (across C1) the leads can be short.
Mike,
First thing you should keep in mind is the optimum tube load
impedance, loaded Q, and the Q you need are all just
approximations. There isn't any need to get over-precise
with what amount to a rule-of-thumb. You generally won't see
a noticeable difference in performance if you are off by a
factor of two or even significantly more so long as
operating Q reasonably exceeds the square root of the
impedance ratios between tube and load in a pi network.
With a 50MHz amp you have to be mindful of distributed and
stray impedances. The stray capacitance and series
inductance of tubes, leads, components, and temporary
connections can have a large effect on 6 meters when
compared to bands like 40 meters.
What type of tuning cap are you using? Is it a flapper
plate, a standard variable, or are you relying on tube
output capacitance? What were the tubes again? How are the
grids grounded? Are the leads from anode to the tank short
and wide?
73 Tom
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