[AMPS] High-SWR protection

[Chuck Counselman]

A few days ago in one of my all-too-frequent mental lapses, I tried to put
200 W of CW RF power into a coax switch while it was set to short the line.
There was a nasty, rich, fat, juicy sounding arc somewhere inside my Icom
IC-775DSP that stopped only when I shut the transmitter off -- which took
me a very long second to do.  I was relieved and impressed that the Icom
still worked afterward.  OTOH, I was disappointed that its protective
circuitry had allowed the arc to happen.  (I wonder whether there's a
deliberate spark gap in there somewhere, or whether I burned some expensive
component to within a micron of the end of its life.)

Naturally I worry about what will happen when I pull the same stunt with my
even-more-expensive high-power amp.  What do AMPS members suggest about
protective circuits?  I hear almost nothing about them, which is
surprising.  It'd be easy to connect a fast relay or solid-state switch to
the exciter/amplifier keying line.  The question is what / how to actuate
that relay.  Wouldn't a simple reflected-power detector do the job?  If
such protection is as simple as I imagine, why isn't it standard in every
hamshack?

73 de Chuck W1HIS



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