[RFI] Keyboard

[Gedas]

You have received some good tips. I would like to add that in a previous 
life when I was a lead tempest engineer I had to design and test items 
like keyboards and the problems we had to overcome, in some cases, are 
somewhat similar to what you are experiencing. Of course the major 
difference was which direction the offending RF was flowing.

Adding the proper ferrite cores, with multiple turns thru each end on 
the main cable is a great place to start since it is easy, inexpensive 
and does not involve ripping open the KB. Replacing the cable with a 
properly shielded one and ensuring that it is properly terminated is 
beyond what most people are prepared to tackle.

Just keep in mind that a typical stock, plastic cased keyboard will not 
impede much RF energy from getting directly into the PCB traces, the 
electronics on the PCB, and all the cables/wires inside the KB itself. 
All of these become receiving antennas & receptors of the RF you are 
transmitting.  The same is true of RF energy escaping the KB leading to 
possible RF issues which was my task to solve. I suspect a pair of 
proper cores will help you out but in the event it does solve your issue 
keep in mind the other possibility I mentioned above, i.e., direct 
impregnation of RF directly through the case and into the KB itself. GL 
es 73

Gedas, W8BYA

Gallery at http://w8bya.com
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On 3/3/2018 10:24 AM, Joe 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