[RFI] Keyboard RFI

[Jim Brown]

On 8/22/2013 11:19 AM, Charlie Gallo wrote:
> On 8/22/2013 Jim Brown wrote:
>
>> On 8/22/2013 10:03 AM, Charlie Gallo wrote:
>>> One odd thing I found - every keyboard around the house (and I have different brands from cheap to Unicomp Model M keyboards) has horrid RFI_IF_  you are close to it (like the hand held within say 6-9 inches)
>> Most trash like this is radiated as a common mode signal by the cable --
>> in other words, the cable is a transmitting antenna.
> Jim,
> Forgot to point out that I did try choking the cable, no good.

HOW did you choke the cable?  How many turns? What frequency(ies) are 
problems?
>   In fact, for instance on this keyboard, cable comes out the RIGHT, signal highest on the left, Mid cable it is not measuring on the radio at all.

That's entirely normal -- that cable is an antenna, so current and 
voltage vary along it's length.

>   Remember I did say this is close distance only.  I might be to paranoid, but...

If you hear it on the cable, it will radiate. Whether the resulting 
field strong enough at your antenna(s) to be heard over other noise will 
depend on lots of things -- distance, angle of the dangle, and what 
other noise is present.

73, Jim K9YC