[Elecraft] K2 K2 QSK?

[jerry]

So:   Somehow I wound up with two K2s.  I bought the first one because 
it was small - multiband - and QSK.  I have
become enamored of transparent, conversational QSK - the kind where your 
transmitted signal just sounds like all the other signals.  The K2 alas 
is not that, although it is PIN diode switched.  I don't think any 
commercial transceiver is.

   Got K2 #2 to get the KPA100.  Moved the KPA100 to #1, because #1 has 
all the good mods - the PLL mod, the volume control mod, the upgraded 
crystals, etc.

  The closest I have been to really good QSK is a QRP-labs QCX+ kit.  But 
it's only one band, and the receiver is probably not as good as a K2 
with a crystal filter - and K2 #1 even has the DSP audio filter.  AND it 
lacks AGC.  I was operating field day, a local came on and nearly blew 
me out of my chair :).

   So here's my idea for perfect QSK:  I use the two K2's as a 
transmitter receiver pair.  One on transmit, the other on receive.  
Connect them to the antenna with a custom PIN diode switch.  W6JL has a 
lot of info on that in his QRZ page.
Arrange something like 130dB attenuation.... or whatever 100W ( or 500w 
if I use a linear ) down to a microvolt or two.

  HOWEVER... I really don't want to be synchronizing VFOs all the time.  
So I find some sort of open source transceiver
control program.  And modify it so it tunes TWO radios at the same time.

   How good is QSK on the K4?  Smooth/transparent?  Or 
clicky-choppy-AGC-pumpy?

                         - Jerry KF6VB