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To: <>
Subject: [AMPS] IMD
From: (Steve Thompson)
Date: Tue, 18 Sep 2001 15:48:54 +0100

-----Original Message-----
From: 2 <>
To: Peter Chadwick <>; @AMPS
<>; 'John T. M. Lyles' <>
To: <>
Date: 18 September 2001 14:53
Subject: RE: [AMPS] IMD

>>Rich said:
>>>Few AB1-grid driven. or AB2-GG amplifiers have as much distortion as
>>>modern transceivers.
>>As evidenced by the published test figures on, for example,  the TS2000.
>>Interesting, since modern MOSFET PA's are supposedly very linear.
>//  FETs are more linear than bipolars, however, both need RF-NFB to
>reach the limit of human ability to detect distortion -- i.e. 1 part in
>10,000, or c. -40db below peak amplitude.
So when the spectrum analyser shows -50odd 3rd order IMD out of my 2m
transverter at 15W pep from a bipolar PA with no rf nfb, it's telling lies?
You might find it interesting to investigate the specs of transistors used
in UHF TV transmitters.

Your statement is far too simplistic a generalisation. There's situations
where it's true, but there's many where it's just plain wrong.


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