[Elecraft] K3 TX delay

Edward R. Cole kl7uw at acsalaska.net
Thu Feb 16 13:56:25 EST 2012


Sort of following this thread as I use a sequencer+inhibit on VHF+ 
(with transverters and following amplifiers).  With my sequencer 
delaying K3 RF for about 300ms there is no issue.  QSK not used on CW 
(of course).  My QRO coax relays would not like

But I am finishing my 300w HF amplifier kit and will be using a dc 
open-frame relay for TR switching of RF.  I guess I can time it using 
my dual trace scope and set K3 TX DLY accordingly (amp will be keyed 
with KEYOUT).  I do not use CW very much on HF so QSK with 300w is 
not necessary (or probably possible).  I can always run the K3/10 in 
QRP-QSK, of course.

There is one thing I do not see being addressed in this 
discussion.  Maybe more important than clipping of CW characters is 
avoiding QRO "Hot Switching" of RF.  Calculate the RF voltage for 
several thousand ohms impedance (open circuit) that will result if 
the amp is pumping out "globs" of RF before being connected to a good 
load.  The relay contacts will definitely get burned big time.  And 
maybe your output devices will have a short live-span.


73, Ed - KL7UW, WD2XSH/45
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