[AMPS] CW amplifier progress (well, daydream progress) -- long

[Michael J. Baker]

Vic Rosenthal wrote:
> 
> Goal: 1200-1500 watts CW output, 160-10m.  Reliability under CW contest
> conditions is the first priority.  Low cost is the second.
> 
> Tubes:  I like the 8877, but pulls are getting hard to find and more expensive,
> and I feel (wrongly?) more comfortable with new tubes.  New 8877's are
> outrageously expensive.  I am thinking about a pair of 3-500Z's: they are
> available, not too costly, rugged, and instant-on.  NOS Eimacs are available for
> $330/pr and RF Parts has their own brand of Chinese tubes for $250/pr.  Any
> comments on the RF Parts tubes?
> 
> The 3CX800A7 and 3CX1200A7 are expensive and not instant-on.  Also they have
> somewhat low grid dissipation ratings and I'm afraid of damaging them.
> 
	Just a passing thought from a new guy to the reflector, but not new to
homebrew amps.
	Why not consider either one or two 4CX800 by Svetlana?  Cost is
reasonable at $190 each and the sockets are only $22 each.  Two tubes
would loaf along at 1500 watts output and the design is nothing new. 
Both DownEast Microwave and, I think his name is Andy from England who
posts to this reflector, have the boards for the necessary voltages and
lots of protection for the tetrodes.  Nice stuff.  You could drive the
pair with (a guess here, ok, please dont flame me, ask andy) about 40 to
50 watts and get full output reducing the load on the exciter so
contesting should be no problem.
	I am looking seriously at doing just what I have suggested myself and
making a good, solid, reliable amp with thoes bias boards and using the
methods described by Rich Measures on his home pages about the QSK
system.  For us CW guys, what could be better?  New tubes with a
warranty, guys who have already done most of the homework for us, and a
proven design that won't cost you $2500.  I figure with what I have
already collected and spent, even with the new tubes I should be able to
get it built for under a grand.  Not bad when you consider what you get
used for that money.  NO QSK, NO warc bands, and older ageing
componenets.  BUILD IT, IT WILL BE FUN AND A LEARNING EXPERIANCE, AND IT
WILL SAVE YOU ABOUT HALF THE COST OF A NEW ONE.
	(Just my 2 cents worth.  Your mileage may vary.  Title, tax and dealer
prep not included.)
	Good luck with the project and keep us folks on the reflector posted as
to your progress.
	Nothing smells as good as sucess..
	Best 73, 
	Mike Baker K0QZ, Phoenix (proof God does have a sense of humor.)
> 
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