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[AMPS] Tube IMD/6146/4cx10000

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Subject: [AMPS] Tube IMD/6146/4cx10000
From: (Peter Chadwick)
Date: Mon, 22 Feb 1999 10:23:58 -0000
Carl says:

>Is it worth going beyond -40dB on HF ?  Or even -20 during a contest !

I'd doubt it - though I have seen military specs calling for -60dB on two
tones in the passband such that the 7th order IP's were in band. Since HF
can raeley give 60dB SNR, I don't see the point.......

Rich says:

>?  People purchase automobiles that will go faster than the 65 miles per 
>hour speed limit.  My wife drives one that will go 3db faster.  The 
>8171/4CX10,000D can be run at 10db gain or 20db gain.  

If the amp follows the usual '3 for 1' 3rd order IMD rule, an amp that runs
-40dB 3rd order IMD  at 1kW out should be -34 at 2kW, and -28 at 4kW - a lot
depending where the gain compression falls. So an amp that is very clean is
likely - even with RF feedback - to be capable of considerably more output
than the licenced power.

The feedback circuits that Carl mentions (Cartesian Loop) etc have some
pretty stiff requirements on mixers and so on - not that easy for home brew.


Peter G3RZP

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