>I would be more concerned with the transceivers IMD level than the tube. The
>new generation of radios seem to be spiraling down at an alarming rate.
>Figures of -24 db below 1 of 2 tones is pretty lousy.
>
>Most Tetrodes are hovering around -36 db down on the third order products.
>You have exceptional linear tubes like the 4c1500B, and the 4cx600J which
>have figures in the -40 db range. In the Larger bottles the mighty 4cx10000J
>seems to have a good figure. Although i cant see the point of this tube when
>simply lowering the screen potential of the standard 4cx10000 produces
>similar 3rd order IMD figures with roughly the same output.
** The advantage of the ...J over the standard ...D is that the ...J's
filament/cathode has c. 7A more peak emission -- if it is ever needed.
The result is flatter constant-current curves, especially at the low-end
-- i.e., better linearity.
>I have never
>been able to read an explanation to what in the tube gives it good IMD
>performance, maybe someone can offer an explanation.
** It's got something to do with electron-ballistics and having enough
electrons to do the job at hand. The nitty gritty is beyond me.
cheers, Craig.
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