>In a message dated 97-06-05 10:19:50 EDT from W8JI, you write:
>
><< In the practical world, ALC is actually MORE necessary in a class AB1
> PA. The slightest grid current will send the PA into distortion
> quickly with most AB1 grid driven designs.
>
> The correct way to install ALC in an AB1 PA is to sample PEAK RF grid
> voltage, and activate the ALC as peak positive voltage approaches the
> quantity of negative bias voltage.
>
> In other words, if the bias voltage is -50v, ALC should be activated
> whenever positive RF voltage peaks approach or reach 50 volts. Any
> ALC sampling grid current will be "too late" to do any good, so the
> system has to be a peak voltage detector.
> >>
Would it not be simpler to adjust the bias voltage a bit higher than
minus 50v, so that the grid can't draw distortion-producing grid current,
and then increase the screen V until the ZSAC increases to normal (like
Eimac recommends). Why waste power output unless there is a danger of
exceeding the max. anode current rating?
Rich---
R. L. Measures, 805-386-3734, AG6K
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