[ETO_Alpha] Alpha 78 on 17m and 12m?

[alpha-service]

"Duane C." wrote:
> 
> A club to which I belong has an Alpha 78 amp.  I have not operated the station
in a long time, and have never operated the amp.  However, a question
has arisen
from a new member regarding whether the amp will or can be made to work
on 17m
and 12m.   Does anyone know the answer to this?
> 

Hello Duane,

  Here is some info about using the Alpha 78:

 The best way to run the 78 is to tune up in the CW position to about
500w output, then switch to it to SSB (higher plate voltage) and
continue your tuneup to whatever output you desire.

  The CW / SSB HV settings were made for the old USA FCC power rules,
which were 1.0 kw DC INput on CW or 2.0 kw PEP INput on SSB.  The ratio
of the low to high HV is such that if you tuned up at the CW limit using
the lower HV (CW), you could then just switch to SSB and the amp would
be tuned up correctly for the higher SSB limit.

  It is better for the amp to run the higher HV all the time, it keeps
the grid and plate current low.  Watch the grid current, NEVER exceed
50ma per tube (as stated in the manual).

  For 1500w output, tune the amp with a keyer sending fast dots.  The
grid current will be about 75ma, plate current will be about 1.2A. 
Sending dots at 40 wpm gives about 1/2 of the key-down reading on the
meters.

  When using the BANDPASS function on various bands, keep the antenna
VSWR below 1.5:1.  Higher VSWR can damage the capacitors in the BANDPASS
circuitry, they are not voltage rated as high as the much larger manual
TUNE and LOAD capacitors.  Do not hold the key down at 1500w in the
BANDPASS mode.

  It is normal to have slightly lower output on 10m than the lower
bands.

  Information on tuning up on 17m is on our web site.  Do NOT use the 78
on 12m, the plate choke will burn up.

http://www.alpha-amps.com/html/warcband.htm

-- 
73 - Glenn AE�Q
Alpha/Power
303-473-9232 x 141

------------------------------------------------------
Attention ALPHA & RF CONCEPTS Customers:

Alpha production and service will be closed between 
July 1 and July 12 inclusive.