[Amps] 4CX250 IMD

[w6duv]

Same for the Collins 204C.
Both the 4CX250B pre driver (Class A) and the 4CX250B driver (Class AB) run 
with 1500 VDC plate voltage and drive the 4CX5000 final tube.

Cheers, Dick
PA3DUV
W6DUV


----- Original Message ----- 
From: "Peter Voelpel" <df3kv at t-online.de>
To: <amps at contesting.com>
Sent: Saturday, September 29, 2007 3:31 PM
Subject: Re: [Amps] 4CX250 IMD


> 4CX250B run quite well at 1500V anode voltage in the Racal TA1800 to drive
> the 4CX10000D.
> One 4CX350A works as a wide band pre driver, two in parallel are the tuned
> driver tubes.
> The amp is run with a rf feedback loop from the 4CX10K to the driver.
> When once the original 4CX350A tubes of the driver were replaced on a
> commercial site by the 4CX250B and the bias circuit readjusted, as the
> original tubes were out of stock (only one left), overall IMD dropped from
> -37 to -31db.
>
> 73
> Peter
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of jeremy-ca
>
>
> When run at only 1500V the IMD is acceptable. Im again making the 
> assumption
>
> that the screen is VR tube regulated in Eimacs1961 test.
>
> OTOH, I know of no commercial ham amp that runs any 4CX250 at 1500V and 
> many
>
> hams push them above 2KV which just makes matters worse.
>
>
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