The recent "amps" discussion of which tube to use for building a new CW
amplifier started me thinking ...
If one were building a new amplifier (or buying one of the new commercial
units) what tube or tubes in the case of a pair would one use? Criteria
are reliability at 1500 watts output, tube cost, availability of replacement
tubes if needed in the future and overall relability of the amplifier. The
100 Amp filaments rule out a "super power" solution like the 4CX5000/8170 or
4CX10000/8171 and the 4-1000/8166 seems to be usable only for a homebrew
solution (and then, only if one has a junk box full of them or access to
an old AM station <G>). The present options seem to come down to: (1) a
pair of 3-500Z, (2) a pair of 3CX800, (3) 3CX1200A7, (3) 8877/YU-158,
(4) a pair of 4CX800/GU-47b, or (5) 4CX1600.
Whether one builds an amplifier or purchases a commercial box, the same
general concerns apply. A good builder will pay attention to overall
circuit design (band switch, pi/pi-L losses, cooling, control circuits,
stability, etc.) and someone buying a commercial amplifier should consider
the same factors.
... Joe Subich, W8IK/4 ex-AD8I
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