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[AMPS] Amplifier for CW

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Subject: [AMPS] Amplifier for CW
From: (
Date: Sun, 14 Feb 1999 12:18:35 -0500

On Sat, 13 Feb 1999 15:02:59 -0800 Vic Rosenthal <>
>OK, even though I have a perfectly good working amplifier, reading 
>about all
>these building projects has made me decide that I want to build one 
>too.  Here's
>my question: I'm a CW operator.  I got a mike with my transceiver, but 
>I can't
>find it.  Given this, I'd like to design my amp from the start for CW 

Sounds like a plan.

>My thought was to set the no-signal bias high enough to cut off the 
>current completely.  Then the operating point would be a little past 
>As long as the bias is not high enough to start sharpening up the 
>keying, why
>should I care about IMD?  This would give me more efficiency and 
>simplify the

I dont see where simplification would come in as the component count
doesnt change.

>Any comments or other suggestions?  I'm also open to suggestions for 
>choice of
>tube (preferable) or tubes. 

Since price is a factor, keep the tube choices to those that run
efficiently in the 2000-2500V range. That will greatly simplify tank
circuit parts and prices.

For GG triodes, 3-500Z's and 572B's are hard to beat for price and
performance. Call for a free copy of the Ameritron AL-572 amp manual.
The full output medical pull 8877's from Equipment Recyclers at $190 is a
great price. At 2500V you can expect an easy 1500W.

Tetrodes are fine if you dont mind the added complexity ( altho cheap) of
screen and grid supplies. Parallel operation and swamped grid certainly
is attractive for 3 or even 4 of the 4CX250 series. Tubes and sockets are
everywhere. Dont overlook the Svetlana 4CX400A either, 600W +  out per
tube and they use the 250B series sockets.

There are certainly many other options but I would tend to stay away from
old glass tubes that are becoming increasingly scarce to replace or need
lots of voltage to be efficient.

If you are into less complicated creativity pick up an MLA-2500 with
blown tubes, they can be found in the $250 range. Then adapt to different

73  Carl  KM1H

 I'd like to get between 1000 and 1500 
>watts CW
>output.  Price is a big factor!
>Vic, K2VCO
>Fresno CA
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