Most RFI prevention ferrite 'beads' are aimed at low VHF, at best, through
800 (a stretch) or so MHz. They will do little to nothing for HF RFI.
Homeland Security recommends 61 material for EMP which is predominately
evident in the low to mid HF region. Take several turns through each
bead. Any more than three physical turns through each bead is reaching the
limit on what a single bead can accomplish.
Placement is best installed at the source or where the particular USB plugs
into the PC. I have installed a bead at both ends of the USB cable with
two physical turns through each. The most aggressive or largest bead would
likely be best installed at the PC.
Dave - WØLEV
On Sat, Mar 3, 2018 at 3:24 PM, Joe <nss@mwt.net> wrote:
> Is RF getting into a keyboard issue OK here, it is RFI in a way..
>
> OK, Say you get RF into a USB keyboard. It just stops working and the only
> way to get it working again is a total re-boot.
>
> I'm assuming the best option is ferrite beads on the cable.
>
> Now question, where is the best placement of the beads. Keyboard end?
> Computer end? BOTH?
>
> I have two here, a small one where I could get one or two passes through
> the hole. ( it is a Radio Shack split thing )
>
> and then a much larger one, also split,, but the hole is close to a inch
> ID. so I could do many turns.
>
> What would be best to put where?
>
> Joe WB9SBD
> --
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--
*Dave - WØLEV*
*Just Let Darwin Work*
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