[Amps] Alpha 78 on 17 Meters

[Kenneth D. Grimm, K4XL]

Michael Tope wrote:

>----- 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......................................
>
Yes, everything that Mike said is right.  The settings for 17 Mx for my 
78 are: 

Bandswitch on 21 MHz, Tune control 18 and Load control 75.

Good luck and 73,

---
Ken K4XL

k4xl at arrl.net

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