Mark Birks wrote:

<SNIP>

>A unit with a keyboard and mouse output (both PS/2 type connectors)
>passes class B with no problems UNTIL a keyboard and mouse are attached.

>Obviously the internal noise of the unit is being radiated out from the
>cables.

<SNIP>

Mark,

Just my 2 cents, but it is not obvious to me that the internal noise of
your unit is being radiated out.  If the keyboard is a PS/2 type (i.e.
IBM PC-compatible keyboard) then it probably has an 8042 CPU in it, and
_that_ might be the source of the EMR that you are experiencing.  As an
extra clue, you stated that the EMR seemed to go away when the _keyboard_
(not the cables) was placed on a ground plane.

If it is possible, try to measure the frequency of the EMR and then see
if it is coming from your project (i.e. your 27MHz signals or multiples
thereof), or the keyboard, or the mouse.

Just a thought...I hope it helps.

Michael