[AMRadio] Filament choke


Larry Szendrei ne1s at millenicom.com
Wed Apr 29 17:12:27 EDT 2009


One way to make an under-sized filament choke (from an inductance
point-of-view) work is to parallel-resonate it at the desired frequency of
operation with a capacitor. Practically, you can do this by adding the
required capacitance to the input tuned circuit. On the two GG amps I
built I use switched low-Q pi-nets on the input, so that meant for 160M
the capacitor on the filament side of the pi-net "grew" in value, over
what it would have otherwise been. Also works for parallel-resonant input
nets, of course.

I got the idea from Rich Measure's web pages; he explains it in detail there.

73,
-Larry/NE1S


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