[Icom] Driving Older Amps

[Mike Clarson]

 Most of the response thusfar have related to the interfacing of older amps
to newer solid state amps. Keying, relay connections etc. Resolving those
get you on the air, but may introduce some more subtle problems. Most older
amps use a compromise in their input circuit--too low a "Q". This results in
input circuits that cover entire bands without retuning, but, present a
varing load to the exciter. A minor problem with tube finals, but could be a
big problem with broadband solid state finals. Current solid state units
fold back output power, and you may find it difficult to drive the amp to
full power. Older units (my Kenwood TS-180S is a perfect example of this)
may shut down if there is a mismatch, resulting in NO power until the
mismatch is corrected. I resolved the problem by using an SGC-239 autotuner
between rig and amp (in my case, a Heath SB-221) and no more problems in the
drive area. --Mike, WV2ZOW