[Amps] 4CX1500B project

[Vic K2VCO]

That's an idea. I was thinking about a CW/SSB switch labeled "IMD ON/OFF". It could change 
plate, grid and screen voltages.

I don't think I'll go as far as class C, though. I can get 1500 watts in AB1 without 
having to worry about additional harmonic output or sharpening the keying. It might not 
even be possible: this tube has only a few watts of grid dissipation so you don't want to 
drive the grid positive.

On 8/9/2012 8:42 AM, Carl wrote:
> 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 at gmail.com>
> To: "Amps reflector" <amps at 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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>

-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/