Hi. I've discovered an unusual problem on the Alpha 87A and wonder if
anyone else has run into it.
If you set the amp to operate on 1.8 MHz or 3.5 MHz, then change bands by
RF sensing to any frequency in the range 7.000 to 7.020, the tuning is way
off (low power, high plate current.) The reason the tuning is off is that
the plate choke relay is not being activated for this one subsegment of
40M. This only happens when switching from the two lower bands because the
plate choke relay is turned off for them. When RF switching to the lowest
part of 40 from any higher band, everything is fine because the plate choke
relay is already on.
The problem can be corrected by pressing either the band switch or one of
the segment buttons (then you hear a loud click as the "clapper" hits the
plate choke.) Evidently, the error only occurs when RF switching and not
when manual switching.
Suspecting a software bug, I contacted Alpha and they're looking into it.
Meanwhile, one person on the local cluster says he's found this problem on
every Alpha 87A he's tried.
Anybody else noticed this one? If you want to try it on your amp, just set
it to operate on 3.5 MHZ, set your transciver to 7.010, then hit the key.
You will hear the smooth operation of the band switch and tune/load caps,
but you will not hear the plate choke relay clack. The tuning will be off.
Push the 40M band button or the first segment button, and you will hear a
clack. Tuning will return to normal.
Note that if you happened to tune the amp for the lowest segment of 40
after RF switching from 160 or 80, then you won't see the problem. Instead,
you will see it if you switch from one of the higher bands to that segment.
If you detect the problem on your 87A, let me know the firmware rev number
and the approximate date of purchase or manufacture. I'd appreaciate any
feedback. Thanks
73, Dick, WC1M
dick.green@valley.net
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