[Amps] Alpha 78 in Digital Modes

[Jerry Kaidor]

I actually bought my Alpha 78 because of digital modes.  My 30L-1 just
wouldn't handle them.  I got a little flak on Eham because I mentioned it
- people were telling me - you shouldn't be running more than 20 or 30W on
PSK.  Personally, I thought they were full of it.  PSK seems to work just
like other modes - people don't hear you, you press the big switch and
then they do hear you.  It's not WSPR.  Somewhere I read a comparison of
low-signal performance of digital modes, and PSK was about as good as
RTTY.

   Still, everybody I QSO says - 20 or 30 Watts.  I wonder how many of'em
are lying? :).

   I am careful to keep things linear - I turn the power down on my TS590S,
make sure there's no ALC showing, and verify that the crossovers on the
PSK waveform are nice and clean on my monitor scope.

                         - Jerry Kaidor, KF6VB

> I have an Alpha 78 and just started using it for digital modes (RTTY &
> PSK-31). I also have a supplemental fan, sold by Alpha, mounted on the
> back of the '78 providing additional air flow. The cabinet is sealed as
> best as I can to maximize that airflow. Now I have a couple of questions:
> 1. What is the maximum power output the '78 should run in these modes
> (essentially 100% duty cycle)?
> 2. What is the maximum air temperature I should allow coming out of the
> top of the cabinet, above the tubes? (I intend to put a small temperature
> probe above one of the tubes to turn the supplemental fan on and off as
> required as it is louder than I would like. That way I don't have to
> listen to it when the amp is idling and when I make a quick QSO, but will
> come on with a resonable temperature rise. The side benefit is that I can
> see when the tubes are running too hot, also.)
>
> Allen Brier N5XZ / KL5DX
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