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Re: [Amps] 4CX1500B project

To: "Vic K2VCO" <k2vco.vic@gmail.com>, "Amps reflector" <amps@contesting.com>
Subject: Re: [Amps] 4CX1500B project
From: "Carl" <km1h@jeremy.mv.com>
Date: Thu, 9 Aug 2012 11:42:19 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Have you considered using a switchable PS that runs FWB and FWD? One switch 
or vacuum relay and you have 2 voltages. Consider 3500VDC for Class C (not 
too deep on the bias tho) CW and 1750V for a real clean SSB.

Carl
KM1H


----- Original Message ----- 
From: "Vic K2VCO" <k2vco.vic@gmail.com>
To: "Amps reflector" <amps@contesting.com>
Sent: Wednesday, August 08, 2012 11:06 PM
Subject: [Amps] 4CX1500B project


> I've been thinking about my next project for some time, and I can't seem 
> to shake the idea
> of an 160-10M amplifier using the 4CX1500B. The tubes and the beautiful 
> SK-800B socket are
> just burning a hole in my workbench, as it were.
>
> So I am thinking of running it in AB1 according to the parameters in the 
> 4CX1000 datasheet
> -- 3kV on the plate, 325V on the screen and -60V bias. This will give me 
> full legal output
> from one tube.  It is possible to reduce the bias and screen voltage and 
> run it closer to
> class A for much better IMD, but as a CW operator I'd prefer a few more 
> watts (actually, a
> CW/SSB switch is a possibility).
>
> I am considering a grid-driven circuit with a 50 ohm swamping resistor. It 
> seems to me
> that it would require 60v peak to just overcome the bias, which comes out 
> to 72 watts
> drive for AB1 operation. Is this a reasonable assumption?
>
> This configuration would make it unnecessary to build and fiddle with a 
> tuned input
> circuit. I'm also thinking about using the G3SEK tetrode board, which 
> would solve a lot of
> little problems in one package.
>
> Does anyone have comments or suggestions?
>
> -- 
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco/
>
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>
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