I think your idea of putting a noisey mother board inside an aluminum
box for shielding is a reasonable one. The problem may be that the
aluminum box your're thinking of as a shield, looks like an antenna to
your VHF receiver. You need to make the potential of the shield box be
the same as the ground of the receiver. The lower he inductance this
connection is, the more alike the grounds will be and the receiver
won't be able to notice the potential of the case going up and down at
100MHz.

Some other things, make sure the ground of your MOBO is connected with
a thick stap to the case.

Solving EMI problems is like peeling an onion. Each layer makes you
wanna cry. You hit the low order effects first because they have the
largest effect and are easiest to fix. Eventually you get to a place
of diminishing returns (EMI gaskets, etc) were you can live with the
"birds" and squelch them out and live with the loss of sensitivity on
some channels of your receiver.

Regards

jcpearce wrote:
As a pet/learning project I made a data aquisition unit using an 8051
microprocessor and an EPIA M motherboard running a variant of Linux
to
process and display the information. It all works but the EMI from
the
EPIA M causes way too much noise to the aircraft radios. I have tried
shielding the whole device in an aluminum case with very little
improvement.

Any ideas on how to smother the EMI or some other small motherboard
which may not have as much an issue (as a test I took my portable
aviation radio and within 6' of any my home computers the same occurs
which gives me little hope)

Thanks