On Sat, 2010-01-09 at 20:54 -0800, Dennis Ashworth wrote:
> More information on the low power condition discussed below:
>
> I suspect the inaccurate SWR reading on the internal meter is causing
> the drive to be reduced to the driver/finals. The drive reduction
> feedback loop is a protective circuit to keep from damaging the finals
> when improper loads are encountered. I'll bet the inaccurate SWR
> readings (3.:1 into a dummy load) are caused by one or both defective
> Schottky diodes in the SWR directional coupler circuit. Does this sound
> reasonable? Has anyone seen this before? Other things to check?
That has been reported on this forum in the past. Bad diodes upset the
ALC. New diodes and it all worked great again. Sometimes the diodes were
germanium, like 1N34A. One of the worlds lowest quality diodes with the
poorest quality control because germanium is inherently very leaky. I'd
wish for something like 1N5711 Schottky instead, maybe 1SS99 very low
barrier Schottky.
>
> Dennis, K7FL
>
73, Jerry, K0CQ
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