[AMRadio] Filament choke


Edward Swynar gswynar at durham.net
Wed Apr 29 15:24:09 EDT 2009


Hi Steve,

There are AIR CORE filament choke designs, too, BTW...

How extensive is your collection of QST magazines? Have a look at those
pieces that featured monoband 160 circuits, and you might hit paydirt. I
KNOW that I saw one either there, or in one of the ARRL HANDBOOKS.

There ARE always options!

~73~ Eddy VE3CUI - VE3XZ


*******************************


----- Original Message -----
From: "rbethman" <rbethman at comcast.net>
To: "Discussion of AM Radio in the Amateur Service"
<amradio at mailman.qth.net>
Sent: Wednesday, April 29, 2009 2:47 PM
Subject: Re: [AMRadio] Filament choke


> 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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> --
> Bob - NØDGN
>
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