[AMPS] alpha input swamp circuit

[Colin Lamb]

  Rich said:

"1.6:1 is enough to cause significant power reduction in many radios."

Since the Alpha 76A requires less than full output of the driver to reach
full power output, power foldback is not relevant.  As long as the amplifier
reaches full output and the driver is protected everyone ought to be happy.

I have a dual 3-400 amplifier and an Alpha 76A.  The 3-400 has the
traditional tuned input.  The 76A has no tuned input.

The 3-400 amplifier is operating properly and the output is consistent with
what others have published in imd tests. My test equipment is a Tektronix
2710 Spectrum Analyzer.  The Alpha 76A, however, is cleaner.  The point is
that the entire package and tube must be considered rather than focusing on
just one issue.  In both cases, my amplifier is cleaner than than the
transceiver driving it, and that is a respected transceiver.  I modified one
of my Alphas (a 76PA) to use the 3CX800A7 tubes but retained the same input.
It showed a better imd performance.

Colin  K7FM



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