[AMRadio] Filament choke

rbethman rbethman at comcast.net
Wed Apr 29 14:47:29 EDT 2009

 From reading past messages from 2007, the FC-30 by B&W doesn't have 
enough inductance for 160M.  The specs are from 3.5MHz and up.

You'd be better off checking some of Orr's Handbooks for the correct 
ferrite rod and wind your own.

I know I have a home-wound one here, BUT - I don't know if it would work 
for 160M.  I didn't build it.

Bob - N0DGN

sbjohnston at aol.com wrote:
> I'm building a 160m grounded-grid amp around the GI-7B tube
> (it worked so well in my SB-230 retrofit project:
> http://www.wd8das.net/SB230.html    )
> Anyone know of a source for a filament choke appropriate for this tube? 
>   The filament draws only 2 amps, so the 30-amp ones I see available 
> online are really overkill (and awfully large).  But for 160m I'm 
> thinking that a somewhat higher inductance than might normally be used 
> for 80-10m amps might be in order.  Say >50 uH?.  Bifilar-wound would 
> be best, but two separate chokes would probably work too.
> Should I not find a ready-made source, then I guess I could make one if 
> I find some ferrite rod suitable for use at 1.9 MHz.
> Thanks...
> Steve WD8DAS
> sbjohnston at aol.com
> http://www.wd8das.net/
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