Tom, start here at the Fair-Rite site.
http://www.fair-rite.com/cgibin/catalog.pgm#select:where4
Click on the big blue buttons for Suppression, then Cables, then either
Round Cable EMI Cores or Round Cable Snap-Its, and find #31 material. The
chart seems to default to #31, but there are tabs at the top of the chart
where you can select other types of material.
The ferrites come in all sizes. The stacked pair I described earlier is
1.40" I.D. and I could get 6 turns of RG-59 size coax through it. But for
the smaller audio/video cables you've got running to your DVR, at least...
you might be able to use the smaller, less expensive ones. I see that
#2631803802 (second from the bottom) is the size I referred to above. It's
2.40" O.D. There's one more size larger: 4" O.D. In general, you just want
to get as many turns as possible through the toroid, so you have to take
into account the size of your various cables' end fittings.
Howard N7SO
On Tue, Nov 2, 2010 at 1:31 PM, Tom Horton <k5iid@sbcglobal.net> wrote:
> Howard, Kelly,
> Thanks for the suggestions. What diameter are you talking about? Beads,
> snap ons, or multi winding cores?
> Wher can I get larger mix 31 cores if so?
> Thanks...
> Tom K5IID
>
> --- On *Tue, 11/2/10, Howard Lester <howard220@gmail.com>* wrote:
>
>
> From: Howard Lester <howard220@gmail.com>
> Subject: Re: [RFI] Direct TV DVR problems
> To: rfi@contesting.com
> Date: Tuesday, November 2, 2010, 11:41 AM
>
> Along that line, my DirecTV HD receiver made loud thumping noises when I
> transmitted with 100w on 30 meters. I found two old 1-3/8" I.D. toroids
> taped together, possibly a 73 or 77 mix, wrapped as many turns of the
> incoming coax around it, and the thumping disappeared. 31 mix would be my
> choice nowadays.
>
> Howard N7SO
>
>
>
> On Tue, Nov 2, 2010 at 12:29 PM, Kelly Johnson
> <n6kj.kelly@gmail.com<http://us.mc821.mail.yahoo.com/mc/compose?to=n6kj.kelly@gmail.com>>
> wrote:
>
> > Mix 31 toroids on all wires entering the DVR is my best suggestion.
> >
> > I've had DirecTV for nearly 10 years and have had no problems with RFI
> > even while running 1KW into low dipoles. I had a TIVO DirecTV DVR in
> > the past with no issues and now I have the newer DirecTV HD DVR. No
> > problems with either of them.
> >
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>
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