[Elecraft] Fix the old amplifier......leave the K3 alone!

[AD6XY - Mike]

I agree an inhibit pin is a very good idea. One must always remember to
connect it of course. The system needs to fail safe. QSK is not used above
HF as much and a radio that automatically allows a delay is far safer than
one that produces power immediately unless an inhibit line is used. If that
inhibit line was an enable line, I think it would be far safer still.

For those who naively carp one should simply speed up ones amplifier - be
aware that there are several things that must happen in the correct
sequence. The RF relays must switch and settle, then the PA bias must
switch, e.g. 350V to the screens for a tetrode. All this before the RF
arrives. At HF this is easy, just use a pin diode or a vacuum relay for RF
and a triode. At VHF is is much harder. PIN diodes are too detrimental to
the noise figure for RF and the 350V screen supply tends to need a relay
because of the shunt regulation. Good chunky high power coaxial RF relays
available for sensible prices tend to be slow, even with a speed up circuit.
They may switch in a few mS but the contacts may bounce for considerably
longer. The TX might not mind but the isolation will be poor and the
pre-amplifier will suffer. 

When you are switching a kW VHF amplifier all this really matters and asking
for it to be done in less than 10mS is a challenge. Most of it is the RF
relays and although small SMA relays do switch RF very quickly, they are
only good for a few 100W. 

There are many K3 features that are totally useless for me. I don't suggest
removing top band or AM to save money because I don't need it, so please
don't suggest useful firmware features are unnecessary just because you
don't need them.
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