[Amps] New SB-200 owner

[jeremy-ca]

----- Original Message ----- 
From: "Steve Thompson" <g8gsq at eltac.co.uk>
To: <amps at contesting.com>
Sent: Thursday, September 27, 2007 9:36 AM
Subject: Re: [Amps] New SB-200 owner


>
>> The 4CX250 family is another very poor choice. They were not developed 
>> for
>> SSB use and the linearity is only in the mid 20's under the best of
>> conditions. This includes the 250R. Ian, G3SEK/GM3SEK, has written
>> extensively on that subject and even developed a set of bias regulators 
>> to
>> at least improve the IMD a bit.
> I think they can do better linearity than that - the amps I built have
> all done so at 250-300W/tube. The STC data sheet for 4CX250B gives IMD
> figures under the typical operating conditions. At 2kV, 325W pep output
> they give IMD3 -30dBc and IMD5 -50dBc. That's in line with what I've seen.
>
> Steve

Which method of testing do you use and did you read Toms recent post? There 
is a huge difference between true real world IMD and the advertising 
departments way of rating it.

Carl
KM1H