[Amps] New SB-200 owner

[Steve Thompson]

> 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