[AMRadio] Filament choke

David Folger dbfolger at yahoo.com
Thu Apr 30 11:46:32 EDT 2009

I hope I did this right as I've never posted or replied to this list before.

FWIW: On the topic of filament chokes, in Orr's 1959 Handbook, on page 628, there is a discussion of a "Practical Cathode Driven Amp" based on 803 Pentodes.

All three grids are grounded, and the cathode driven. 

He does not use a filament choke. In the text he claims it isn't necessary below 7MHz. I guess the thinking is that there is plenty of inductance in the filament transformer windings to present a high impedance to the RF. At higher frequencies, however, capacitance to ground in the transformer is a problem and he recommends a filament choke in that case (at least that is my interpretation of what is going on).

This handbook has fallen into the public domain and is available in several places on the Web including:



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