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[Amps] bangs in 3cx800

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Subject: [Amps] bangs in 3cx800
From: (2)
Date: Sat, 24 Aug 2002 15:54:44 -0700
To be clean, tetrode and pentode amplifiers should be tuned to the tube 
mfg's specified screen current, when peaked with the Tune-C.  Less screen 
current =s heavier loading =s less imd.  Zero grid current is cleaner.  

>> 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

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,  

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