[Amps] Be advised: K3 TX DLY differs from documentation

[Jim Garland]

A well-designed amplifier QSK circuit should never allow hot-switching 
of the amplifier's T/R relays under any circumstances. There are several 
ways to accomplish this goal, none of them expensive or complicated. For 
example, in my own QSK design (QST June 2015, expanded info at 
http://www.w8zr.net/QSK), there are two modes of operation. The first is 
"semi break-in", where the only control line to the amplifier is the 
ordinary relay output from transceiver.

The other mode is "full break-in" which routes the keying line through 
the amplifier's QSK-IN and QSK-OUT jacks before it reaches the 
transceiver. In this mode, the amplifier is ready to receive RF before 
the transceiver begins to transmit. In both modes, however, the 
amplifier will not key up if RF is prematurely present at its input, and 
all internal amplifier relay and bias sequencing is done properly.

For operators running semi break-in with any amplifier, whether QSK or 
not, is it is necessary to set the transceiver's TX Delay menu setting 
to give advance warning to the amplifier that RF will shortly be on its 
way. For my design, the amp simply won't key up if this warning is too 
short, so choosing the correct setting is easily done. The K3's default 
setting of 8 mS is plenty long enough for most modern amplifiers. With 
the Flex, shorter delays are possible and can be found by trial and 
error. In the full break-in mode, it doesn't matter how fast or slow the 
amp relays are, because there is never any possibility of hot-switching.
73,
Jim W8ZR
>> Consider, for example, the K3 and Flex 6000 series transceivers. The K3
>> defaults to an 8msec delay, through menu setting TX DLY, and is
>> djustable up to 20msec.
>   N7YK discovered...that his K3 was hot switching his homebrew QSK
> amplifier.  I repeated his measurements using a scope on my K3.  Both
> radios had the KSYN3A synthesizer upgrade, which apparently changed
> things.  I also measured a friend's K3 that did NOT have the KSYN3A
> upgrade, and the results were quite different.
> 73,
> Bob, N6TV
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps