[Amps] 4CX250 IMD

[jeremy-ca]

----- Original Message ----- 
From: "Steve Thompson" <g8gsq at eltac.co.uk>
To: <amps at contesting.com>
Sent: Friday, September 28, 2007 2:30 AM
Subject: Re: [Amps] 4CX250 IMD


> jeremy-ca wrote:
>> According to my full size Eimac manual ( the yellow one with the multi
>> page spec loose leaf sheets) the only 4CX250 style tube with decent IMD
>> is the 4CX250R/7580 which was used in a lot of military equipment
>> including the AN/URC-32 that I worked on in the USN.
>>
>> At Ep of 1500 in AB1 3rd/5th is -30/35. However at 2000V it slips to
>> -23/27.
>
> At what power and efficiency?
>
> Steve
>

250/245 ma and 262/470 W PEP Note they specify PEP. There is also a "worst 
case" 3rd order line entry of -29/21dB.

With the tendency to use these tubes (the full 250 family)at their maximum 
voltage and their, even today, popularity on VHF/UHF it is no wonder they 
get a rap in crowded areas.

Ive another low priority project waiting for its turn. I was given a home 
brew PP 6 &  2M 4CX250 amp by a long time friend who moved into a senior 
housing village. It would be a perfect platform to experiment on as Ive a 
few dozen tubes on hand from new to unknown. My intention is to use it at 
our summer cottage on the coast of Maine after improving IMD.

Carl
KM1H