> Roger is correct. Fast (semi break-in) works very well and is better
> and safer for equipment than QSK.
I like the advice of Vic, 4X6GP where he wrote:
"Personally I use full QSK less than 10% of the time, but I would want a
QSK-capable amp even if I never used it."
Fast switching speed isn't only for CW operation. AMTOR, what may now be an
obsolete mode, requires fast T/R switching speed. But even if AMTOR isn't
popular today, I would want my amps ready for tomorrow's new AMTOR, whatever
that may be. This, in addition to fast switching for CW.
Elecraft took a risk by implementing PIN diode T/R switching into the K3,
KPA500, and KPA1500. They took an evolutionary approach, starting with the
K3, then built on that experience to confidently design higher power
versions into their amps. No doubt there were "lessons learned" along the
way. Some of those lessons probably pre-dated the K3 by studying legacy PIN
designs from DEO, ETO , and Ameritron.
My homebrewed PIN diode T/R circuits cost less than $20, operate at 2KW with
no issues, are fully SWR protected, and have approx. 0.25 dB of insertion
loss. If I can do it for that cost, a manufacturer should be able to do it
for less in volume.
Probably the trickiest part of the design is back-biasing Rx PIN diodes with
moderately high DC voltage. This in and of itself may scare-off
manufacturers in addition to the nightmarish thought of what could happen if
they don't design it right and they're consumed with warranty repairs. So,
they take the safe, easy, and cheap route by mostly using modern automotive
frame relays, and rarely design with more expensive vacuum relays.
Paul, W9AC
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