[Amps] RE: 4CX250B Screen Supplies

[DEHAYS Dominique]

The zener chain or the OA2-OB2 VR tubes must be considered as "antique" 
technology. We hams have one duty : make our transmitted signal as clean 
as possible , not only for the harmonic content , but also to enable 
others to work on the band at the same time we are on it. Just have a look 
at:
http://www.ifwtech.co.uk/g3sek/cleansig/imd1.htm
There are some IMD curves drawn for a 2*4CX250R amp , with modern screen 
regulator , and zener chain regulator , you 'll see it simply makes 10db 
degradation on IMD3 . You will notice too , that the amplifier tested was 
running 500w for a pair of 4CX250R , imagine what is the problem when some 
guys are running the same kind of amp at 1Kw out....
73's Dom F6DRO