[Elecraft] KPA500 with K3 in TUNE mode?

[Phil & Debbie Salas]

The AUXBUS provides one-way communication between the KPA500 and the K3 
(KPA500 to K3).  So the KPA500 won't know that the K3 is in TUNE mode.  The 
KPA500 has about 12-13 dB gain, so if the SG235 can take up to 100 watts 
without problems, you could set the TUNE mode to output no more than 5-watts 
for tuning.  Unfortunately the K3 amp-enable output is always active whether 
in TUNE mode or normal operating mode (I understand this is hard-wired and 
so can't be changed in firmware).

What would be nice is if the K3 would output a signal (Dig Out 0 or Dig Out 
1?) that would feed the amp-inhibit input on the KPA500 (pin 11) when you 
press TUNE on the K3.  Not sure if this is possible, but that would do the 
trick.

Phil - AD5X

"I'm busily preparing for my new KPA500 and working out all the station
interface details. One of my antennas uses an SGC SG-235 remote tuner,
which will support the amp's 500W output but must be tuned at lower
power. I currently just hold the K3's TUNE button to generate about 20W
to tune the SG-235. Once the tuner has found and memorized a match at a
given frequency, it only takes a very short burst of low power RF to
reset on QSY, but it really needs to be done at 100W or less. This is no
problem with the barefoot K3 -- I can recall the tune setup with a
couple of dashes from the keyer.  This technique would be disastrous
once the KPA500 is online, so I'm clearly going to need a way to
initially transmit at lower power after a band change to wake the tuner
up. I realize I could select the menu option to drop the amp offline
after every band change, but since I need to turn the amp off only with
one of several antennas, this is a lot of ergonomic overhead.

With the K3 and KPA500 integrated and talking via the AUXBUS will the
firmware keep the amp  offline when the K3 is in TUNE mode? This would
be really useful for my particular setup, and for anyone who uses a
remote tuner. I've looked over the manual for the KPA500 and it says
nothing about the behavior in this case.

If the amp stays live in TUNE, perhaps a future revision of the firmware
could present a menu item to let the user choose whether or not the amp
will be enabled in TUNE mode.

73...
Randy, W8FN"