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[Amps] bangs in 3cx800

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Subject: [Amps] bangs in 3cx800
From: (Paul Christensen)
Date: Sat, 24 Aug 2002 17:17:48 -0400
> tube and the regulated supplies.  I question whether the splatter Paul had
> was related to the amplifier at all.  I suspect that the amplifier was
> overdriven by the driver and flat-topped.  If ALC was used, this would be
> almost certainty.

Recall that the 2000A is a true auto-tune amp and it performs this function
remarkably well...even better than the Alpha 87A in my opinion.  If the amp
is misadjusted during tune-up, it's the amp's fault (or the designer's), not
mine.  Nevertheless, the amp can be manually tuned as well with similar
results.  I never use ALC and my exciters exhibit zero power overshoot; the
exciter's internal ALC circuits are all working properly.  I monitor my
output with a scope through a Bird ThruLine sample 100% of the time on SSB.

I am painfully aware of the effect of flat-topping and excessive overdrive.
The splattering did in fact worsen when lower drive levels were prevalent at
the amp's input.  This was not an overdrive issue.  What I am saying is in
that particular amplifier, there was an intermod-related problem which does
not manifest from either of my Alphas.  I have three exciters here from
which to use.  The problem was apparent with all exciters when used with the
ACOM 2000A.  Was the problem limited to that particular amp?  Perhaps it
was.  Perhaps it wasn't.  Correctly measuring 3rd-order intermod is no
trivial matter and is far beyond the capabilities of my station equipment.
My solution was simple: I sold the ACOM and kept the Alphas.

-Paul, W9AC

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