[Amps] Alpha 78 on 17 Meters

[Michael Tope]

----- Original Message ----- 
From: "Frank N. Haas" <kb4t at arrl.net>

> What is the best method to put an Alpha 78 on 17 Meters?
>
> This model of Alpha normally doesn't require tuning in the conventional
> sense on 80, 40, 20, 15 and 10 because of its broadband ("bandpass") 
> output
> stage. However, one can switch to a conventional tuning mode, if desired.
>
> Neither the conventional tuning method or the bandpass setup for 20 or 15
> meters produces any output on 17 meters.
>

Frank,

The tuning is pretty sharp for 17 meters. In fact, the first time I tried 
it, I
concluded that it wouldn't work on 17 meters at all. The club I belong
to has 2 Alpha 78's. Recently I had one over here to replace a burnt
bandswitch. With some careful fiddling, I was able to get full output on 17
meters. Unfortuntately, the amplifier is at the club station now, so I don't
have the tune/load control settings chart in front of me. I believe I was
able to get it working using the manual tune position with the bandswitch
set to 21 MHz. Try fiddling with the tune/load controls at a low drive
level (10 watts say). If you carefully work through the various combinations
of tune/load, you  should be able to get it to work. DON'T tuning up on 12
meters, though. The plate choke has a resonance near that frequency and
will likely go up in smoke if you do.

73, Mike W4EF......................................