David L. Thompson wrote:
>
>The 4CX400 is an excellent replacement for the 8873, 8875, and 8122 in the
>NCL-2000. They average about $135 each retail amateur net.
It's also an excellent replacement for the 4CX250/B/R, but it needs
power supply modifications to realize the full potential.
With 2500V on the anodes and 375-400V on the screens, a pair of 4CX400As
will give 1000-1100W output on 6m or 2m in the classic W2GN amplifiers.
Operating condx are exactly as specified by Svetlana, allowing 1-2mA
grid current per tube. In strict class AB1 (zero grid current) the power
ouput is an even kilowatt.
Grid drive requirements are very low indeed - for example 10W on 2m with
120 ohms grid damping, or 2.5W on 6m with 250 ohms damping.
Apart from larger anode contact rings, chimneys and exhaust holes, no
other RF-deck modifications seem to be required.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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