I currently have an Ameritron AL-80B, driven by an Icom IC-765. With the
ALC backed all the way off, a string of dots or dashes produces a constant
RF output level on my peak-reading wattmeter. If I run the 765 output up to
100W and use the amp's ALC control to reduce the output to rated level, I
see a substantial difference between the output levels with a string of
dashes vs. dots. With dots, the peak level hovers about 150 watts above
that observed with dashes. The same effect is seen on the amp's wattmeter.
When I substituted an Ameritron AL-800H for the 80B, I observed a similar
difference in the levels when using the ALC. I suppose this is related to
the time constant of the ALC in the amp, as I also see a difference in the
ALC voltage output by the amp as seen on the amp's ALC meter. Both of these
amps also have the Electronic Bias Switching circuit, so don't know if that
could also be part of the cause. The difference in output levels appears to
be independent of the CW speed. Any explanation for what's happening, and
it this common when using ALC on other amp brands to control CW output
level?
K8AC
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