[Elecraft] K3 key line timing

[Rick Stealey]

I wanted to report on some measurements I made on my K3 in the process of incorporating 
QSK into my homebrew amplifier.  I think the new vacuum relay for antenna switching and the 
DIP relay for bias switching in the amp are fast enough to support QSK but I wanted
to make a master timing diagram to be sure everything sequences safely to assure
no hot switching can occur.
So I hooked the K3 up to a keyer sending dots at a fast rate and used my scope to 
look at the KEY OUT line and rf envelope running at 4 watts in a dummy load.
I found the KEY line activates 5 ms after key closure, and the rf envelope comes
up a variable time depending on the TX DLY just exactly as expected.
What was most encouraging was the textbook perfect shape of the rf envelope.
5 ms risetime, no sharp edges, no overshoot.  On key up, the rf envelope 
decays to zero after 18 ms, and 12 ms later the KEY OUT line goes high (nice
and safe).  
Conclusion - on key up it is impossible to hot switch.  On key down my amp relays have
13 to 23 ms (depending on the setting of TX DLY) to do their thing before they see
rf.  This should be no problem, but the measurements still have to be made.

Please see my next post on a related topic titled "Are The Bands cleaner with all the 
K3s being used?"

Rick  K2XT