[Amps] Plate choke and bypassing

[Peter Chadwick]

Try figuring it this way:
You have with 2500 dc around 4000v pk to pk, or about 1400 rms on the plate. If the choke reactance is say 2800 ohms, then there's 500mA of RF in the choke, and through the blocking capacitor. This makes it worth while using another choke and cap up to the B+. But the choke needs to be able to handle that current, as does the bypass capacitor. Now 1000pF at 2MHz is about 80 ohms, so there will be about 40volts rms of RF across it. In practice, there's other stuff hung on there that will drop the impedance, but you get the hang of the sort of currents involved.
I've seen a professional Tx that used a solenoid about 4 inches long, close wound with about 22AWG enamelled wire as the feed choke. The HV side of this had a 680pF transmitting type ceramic to ground, and a choke, again 1 inch diameter, consisting of 2 universal wound 'pies', each about 1/4 wide and about 3/8 inch thick - probably about 1mH. Then there was another 5000pF tx type capacitor to ground from the HV. That covered 1.6 to 22 MHz continuous and would go up to 27 at reduced efficiency with no problems ever found at any frequency. PA tubes were a pair of 4-250A.
73
Peter G3RZP