On Thu, 2006-10-26 at 09:56 -0400, John K Gotwals wrote:
> When I operate on 75 meter SSB with my Orion, my computer beeps and
> disconnects/reconnects my USB connected keyboard. Note that I do not have
> this problem on 40 meter SSB. My computer is located on the second floor of
> a brick house, and one end of my dipole is about 15 feet from my shack.
>
> >From comments made by others on this list, I may have to put RF filters on
> the cables and wires connected to my computer. I am contemplating the use of
> Amidon FT-240-77 ferrite toroids, which have an I.D. of 1.4 inches and cost
> $9 each. If I buy in quantities of 10, is there a cheaper source for this
> toroid?
>
> Any comments or suggestions on this problem would be appreciated.
>
Look at Mouser (www.mouser.com) for Fair-Rite EMI suppression Ferrite
Cores. Perhaps something like a split core in Material 31,
623-0431164181. It will fit over a half inch diameter cable for $4.
Where the cable is smaller and since you don't have to thread the cable
and connector through the hole in these split core parts you can go to
something like the 623-0431134951 that has a .200 hole for $1.47. If one
isn't a full cure, you can apply several at that price.
Pick something with high permeability and some rated impedance at 75
meters if possible. Those rated only at VHF won't do much at 75 meters.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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