Joe Subich, W4TV wrote:
Older (tube) radios did not have "power level controls." They
were operated at their design power and ALC reduced the gain
to prevent overdriving the final amplifiers.
This is true.
I used to run PSK31 with a Kenwood TS-520. No power control on that rig
and the ALC circuit was designed to keep from overdriving an external
linear amp, -9V if memory serves. The manual said to keep the ALC
reading on the meter below the top of the arc in SSB to keep from
splattering. It didn't take much turning of the mic gain to go from no
indication (flat needle) to top of the arc.
When I used that radio on PSK I tuned it up to maximum smoke on CW,
switched to USB and had to fiddle with the sound card output and the mic
gain control to get my 30W out with NO action on the ALC scale of the
analog meter. Way different than running straight SSB. Worst IMD reading
I had with that setup was -25dB, most of the time -30 or better.
It must have had a pretty flat filter in it because I didn't see any
power excursions on my peak reading meter while "clicking and pouncing"
in the waterfall of MixW or digipan.
--
R. Kevin Stover, ACØH
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