>
>
>-----Original Message-----
>From: Lamb <k7fm@teleport.com>
>To: W8JI@contesting.com <W8JI@contesting.com>; amps@contesting.com
><amps@contesting.com>
To: <amps@contesting.com>
>Date: 16 August 2001 06:20
>Subject: Re: [AMPS] Tetrode poor IMD performance
>
>
>>
>>While not claiming to know the answer to Tom's question, I would like to
>add
>>some information using a similar tetrode.
>>
>>The 4CX1000 was originally not designed for linear amplifier service.
>Eimac
>>specifies the 3rd order distortion as -23 db and 5th order distortion is
>>specified as -26 db. The Collins 30S-1 used that tube, but used a cathode
>>drive configuration (which has inherent feedback) and applied additional
>>feedback to arrive at a clean amplifier.
>>
>>Without feedback, though, a 4CX1000 with a resistive grid and perfectly
>>stabilized voltages ought to yield no better than a -23 db 3rd order
>>distortion.
>There was a 2m amp described in VHF Comminications some years ago using
>4CX1000A. I don't remember any 2 tone measurements, but there were spectrum
>photos under voice mod. I know voice mod is not a controlled test, but the
>output looked a hell of a lot better than I've seen while bench testing amps
>that did have mid 20's 3rd order products.
>
Amen, Steve
cheers
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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