[Amps] plate chokes little buddy

[John Irwin]

dudes>>>
 
On most tube, hf ,rf, shunt feed, amplifier schematics there is a small RF choke in series with and just below the main plate choke. A  much smaller value in mh than the plate choke, sometimes it is a resistor rather than a choke.  What is the purpose of this second choke and how is it's value determined?
 
Thanks 
john kb9tc


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