My name is Onno de Vries and i'm living in the Netherland and building
big amps is my hobby.
I just bought a 4CX 5000A on a radio market here for a good price (180
Euro) including socket.
Becourse the price was so good i took the challenge to build a 88-108
Mhz final from it.
After some experimenting i found out that the anode resonator is a bit
of a problem course of the high cappacity of the tube.
I try to do it with a double output coil (together Almost a half wave)
wich you see in manny designs for 144 Mhz amateur amps using for
example the russian tube GU84.
This works but it has a terrible efficiency,about 25% with the
4CX5000a tube.

I hope somebody can give me some advice about how to design tank
circuit with a high efficiecy.

Greetings..........Onno.