[Amps] 3CX1000A7 question

[Jan Erik Holm]

> 
> Friends!
> 
> I have a couple of days got a home-built amp
> using a 3CX1000A7 - it deliver around 1200 watts
> out, key down - only tested it on 80 meters.
> 
> It seems that it's built, in the seventies, with
> input circuits from an SB-220. As I think that
> the input impedance for a 3CX1000A7 is around
> 50 ohms can the use of SB-220 input circuits
> be OK? I don't have the input impedance of 
> a pair of 3-500Z's here and have not tested the
> 3CX1000A7 with an SWR-meter between the
> tranceiver and the amp.
>
3CX1000 is about 42 ohm and 3-500Z about 115 ohm,
so inputs for 2 x 3-500Z will work just fine, just
would need a slight tweeking, i e will make about
57.5 ohm.
> 
> I know Rich will object to this  (by the way
> your letter Thursday Rich)  but how about
> not using any input circuits? 
>
I will also strongly object! Please do not run a
cathode driven GG amp without input matching, we
have enough wide signals on the bands already. It
will degrade IMD performance very much.
> 
> Thanks in advance for answers and 73 de
> 
> Osten SM5DQC    sm5dqc at areteadsl.se
>
73 Jim SM2EKM