Mike Tubby wrote:
Page 65 of Eimac's "Care and feeding of power grid tubes" shows a
selection guide for SSB service for which the 4CX250B is listed as
being capable of 348W "useful power output" in AB1 with a 3rd order
distortion product of -25dB (doesn't say whether its relative to
carrier power or one tone of two tones).
Relative to PEP, ie only -19dB relative to either tone.
Eimac were being quite irresponsible by implying that level of IMD is
fit to be put on the air, and that data sheet has given the 4CX250B an
undeserved reputation for poor linearity.
If you're less greedy than Eimac, you can get 250W PEP from a single
tube with excellent linearity.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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