[Amps] Grounded Screen 4CX1500B

[Steve Thompson]

David Kirkby wrote:
> Conrad_G0RUZ wrote:
> 
>>For the uninitiated the weasel or whistle or various other names was the
>>nickname for the push pull 2 x 4CX250B amplifier published by W1SL which got
>>a reputation for not working too well. This was because UK amateurs insisted
>>on using the wrong type of surplus socket.
I've seen them working fine with several different sockets - I've found 
any socket with a built in screen cap is ok at VHF. The original design 
had huge gain, something that was hidden in class C use. It really shows 
when people started piling on the anode volts and linear bias - I 
suspect many just didn't get the neutralising right. Resistively loading 
the grids so it needs 20-30W drive in AB1 makes life much easier.

The big thing I saw was the need to get the loading right. The original 
design loaded lightly - probably to get the efficiency up for cw use, 
but with higher voltage and linear bias it just gives more gain and 
potential problems.

Personally, I hate tuned link coupling, but that's another soapbox....

Steve