[AMPS] Question : 4CX800 Amplifier 6-10-12-15-17-20 meters

Peter Chadwick Peter.Chadwick@zarlink.com
Tue, 4 Dec 2001 16:58:21 -0000


Coiln said;

>There is nothing to be gained by using a tuned input when the
> amplifier is in a grounded cathode configuration.  

This rather depends on the input capacitance of the tube(s) and the value of
grid swamping resistor used. With a highish value resistor (200 ohms) and a 20
or 30 pF of capcitance, the reactive input even when using a 4:1 transmission
line transformer can cause some problems for some solid state rigs. Of course,
anything with a pi network shouldn't have a problem... 

If you can get adequate drive with a 50 ohm swamping resistor though, then even
40pF of input plus stray will only give a 1.5:1 SWR at 30MHz.

73

Peter G3RZP


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