[Amps] QSK (okay, not QSK...)

[Ian White GM3SEK]

Steve Thompson wrote:
>
>
>Jim Tonne wrote:
>>> I think I'm starting to get depressed with this exchange . . .
>>>. . . some others are enjoying it . . .
>>
>>
>> Echos my sentiments.  I just came back from Home Depot
>> after having picked up a fire extinguisher.
>>
>> Awaiting the "we're through with it" comment!   :-)
>Going back to a question posed at the outset about relay life... The
>reflector is not full of people saying that QSK trashes their relays. On
>the other hand, my mental arithmetic (far from reliable these days)
>comes up with an estimate of 120-150k operations for a heavy duty
>contest weekend - a sizeable percentage of expected lifetime. Ensuring
>cold switching will presumably help, but mechanical failure is going to
>be a factor at some point.

In theory... but those active contesters aren't going to be doing all 
that keying by hand. The computer will be doing the bulk of it, and QSK 
is no help there. Most people wouldn't dream of trying to interrupt a 
contest transmission before it's finished, because it probably won't 
work and at best there is only about one second to be gained.

In addition, the most successful single-ops are using SO2R techniques, 
so while they are transmitting they're certainly not listening between 
the dots. They aren't even listening to the sidetone  - they're away 
listening on some other band. (This is also one of the reasons for using 
canned SSB modulation, but I do agree it should either be done elegantly 
or not at all.)

Having said all that, the technical requirements for an amp to support 
full between-the-dots QSK are not much different from those for 
semi-breakin. The basic requirement is that the amp follows the 
instructions coming from the transceiver PTT with minimal delay, a few 
milliseconds at most. That allows the transceiver to take complete 
control of the timing.

For semi-breakin, the PTT line only changes state at the beginning and 
end of the whole transmission - but those changes do need to be fast to 
avoid timing and arcing problems. The only difference for full QSK is 
that the PTT changes state much more often, between every dot and dash - 
what comes out of the transceiver's PTT jack is literally Morse code - 
and the changeovers in the amp need to be a little faster to avoid 
distorting the dots and dashes at high speed.

If the transceiver outputs correctly-timed instructions on its PTT jack, 
and the amp follows those instructions quickly enough, support for full 
QSK is automatic and transparent to the user. The only issue then is the 
relay wear and the noise.



-- 
73 from Ian GM3SEK