John / NS1Z wrote:
>Somewhere in the dark recesses of my mind I remember seeing an article
>about a homebrew amp using a pair of 4CX250s (or 150s). Seems to me it was
>called the plumbers delight or some such.
>
>If any of you kind souls could point me towards a source for construction
>details, it would be greatly appreciated.
The Plumber's Special does work, but there are now better designs that
avoid the problems of lead-screw tuning, and don't blow hot air through
the tuned circuit.
If you want a push-pull amplifier, the W1SL design is a favorite because
it's easier to build than the Plumber's. It was originally published in
QST for February 1971, and updated into the SSB era in 'The VHF/UHF DX
Book' (available from ARRL).
Alternatively there's the W2GN parallel design, which was in Ham Radio
for October 1977.
(Commercial break: Down East Microwave have just taken delivery of kits
for W2GN-type amplifiers updated to use two 4CX400As. With a 2.5kV power
supply, they will give 1.0kW output in class AB1.)
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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