I looked at 50 ohms shunted by 80 pfd -- 2 - 30 mhz - -- series L of 271 nhy and shunt C of 71.5 pfd at input gives better than 23 db return loss from 2 to 30 mhz. I was wondering why Alpha did not l
Id be concerned at how well the match holds over the full input cycle. Carl KM1H _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mail
Thought he was talking about no grid current - but even with grid current what other sort of input network would be any better over the swing with regard to match? I would think , without doing the d
That 1000 Ohms is for 1.5W of drive. Carl KM1H _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps
Why not a 1:4 un-un and a 200 ohm swamping with a 3db pad between the exciter and the un-un Don W4DNR _______________________________________________ Amps mailing list Amps@contesting.com http://list
Hank, I hope someone will correct me if I am wrong but I believe the problem is the changing input impedance the tube/FET etc. throughout the RF cycle for all classes of operation except heavy class
Larry, Can you explain what causes a change in input impedance over the cycle when operating in AB1 i.e no grid current? I can see Miller effect causing some change as the amplitude varies, but not o
Peter, I can't quantify the change which is probably small but a professor I had in a EE class was emphatic about this topic. At the time I probably didn't grasp it completely. There should be a cont
Larry, Thanks. According to Pappenfus, the change in input capacity in 4CX250B due to variation in electron density between grid and cathode is about 0.1pF, which can cause problems with distortion r
Lets see, 50 volt swing on control grid produced 2000 volt swing on plate. Gain during this conductive part of the cycle is 40 so the Miller capacitance during linear part of the cycle is 4.1 pF. The
Bill, Agree with your numbers and conclusion. The magnitude of the effects will depend on the swamping resistor. I calculate that at 30 MHz with a 50 ohm swamp, there will be around a 2 degree phase
REPLY: Where did that figure come from? According to the Eimac 4CX1500B data sheet, the input capacitance in grounded cathode mode is between 75 and 88 pF. 73, Bill W6WRT ____________________________
Sorry, looked up the wrong tube in the wee hours on the morning. But, that was not my real point. In an amplifier with a plate tank circuit with Q>10 the Miller capacitance is not going to change muc