Dear Gene,
I've been following Mr. Measures' research
on parasitic suppression for several years and
have modified the design of every amplifier I've
built and rebuilt in order to incorporate Low-Q
suppressors.
In my latest amplifier that uses dual 3CPX1500A7
triodes running at 4KV there are three distinct areas
of parasitic suppression involving Nichrome wire and
film resistor networks in the pathway from the
RF Choke to the tube anodes
Even if Mr. Measures' research is completely wrong,
the cost to installing these small modifications is minimal
compared to the cost of the rest of the project.
Now if Mr. Measures' research is correct, however,
the minimal cost of protection certainly outweighs the
cost of replacing $1400 ceramic triodes.
The basic premise is that at a VHF or UHF "event,"
the designer wants a high resistance in the pathway
of the oscillating energy. Near VHF, (28MHz.), the anode
Nichrome conductors become warm, especially at
QRO levels, but they are Nichrome, and there is a
constant stream of cooling air through the tank.
Hal Mandel
W4HBM
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