Regarding ALC on Ten Tec gear, here is my understanding of how it works. The
POWER control on most Ten Tec's since at least the Triton series is simply a
front
panel ALC control. In fact, the Tritons and I think the early Omni's labeled
the power
control ALC because that is what it reality is. Later rigs changed the name to
POWER or some version of that but it is still a ALC control. For example,
specifications for the Orion state: "Power Output: ALC Adjustable 5-100 W +/-
1
dB."
Using the term "POWER" in relation to the ALC control is a little misleading
though.
It is really a "maximum (peak) power" control. With the front panel ALC/POWER
control set to a certain power level, the radio will never exceed that power
level but it
is very easy to operate at any power less than that on CW on the older rigs and
SSB
on all TT rigs simply by reducing the microphone level. (Also called DRIVE on
some
earlier Ten Tec's). However, the output is quite linear in that mode of
operation and
so we get very low average power output because of the poor average to peak
ratio
of a perfectly linear un-processed SSB signal. The average power or so called
talk
power can be increased to a point by proper signal processing without exceeding
the
peak power selected. The Orion internal processor is excellent in this regard
and I
hear that the new Ten Tec speech processor is likewise.
Here is where it gets a little confusing though. On CW, rigs up to the Paragon
would
allow operation at any level of CW power equal to or less than the ALC setting,
by
adjusting the DRIVE control. Starting with the Paragon and continuing to
present day
rigs I believe all Ten Tec transmitters set the CW power with the ALC/POWER.
The
only way to reduce CW power is to reduce ALC. I would not be surprised to find
that
is why they changed the name from ALC to POWER. In a sense, this is a step
backward, especially on the Paragon, Omni V and Omni VI. When you first close
the
key on CW, the transmitter strip is running at full or near full gain. Most PA
stages
can produce considerably more than maximum rated power though so the ALC must
reduce drive to the PA to hold at the desired power level. That takes a small
amount
of time during which overshoot develops. It's not bad but it can be
nonexistant in
earlier Ten Tec rigs by proper adjustment of ALC and DRIVE. The software
radios
can deal with that in software and minimize the overshoot matter. But I don't
know to
what extent they do.
Anyway, in summary, on the Orion operating CW, the PWR control sets ALC level
and CW power. On SSB, the PWR control sets ALC level (and the maximum peak
power allowed). The MIC control sets the actual output power from zero to max
allowed by the ALC.
Other Ten Tec's work in similar if not exactly the same fashion.
Now to the question that started this discussion. Here's how I approach
amplifier
tune-up. Place the Orion in CW mode at low power output. Tune the amp for
maximum output, increasing drive power as needed, but do not exceed the
amplifier's plate and grid current specifications. Once you know how much CW
power the amp requires for full output, leave the PWR setting on the Orion at
that
level. You're ready to go on CW. On SSB, tune the amp as you would for CW
then
switch to SSB and adjust the MIC setting and insert some speech processing to
get
the talk power you desire. I usually run a SP setting around 6 and just keep
the ALC
led blinking on peaks.
73 all,
-Lee-
WA3FIY
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