Thanks for the suggestions, no I have not posted what I did anywhere
but I think I will as it took me a little while to learn rudimentary
assembly, come up with a variant of linux running off flash memory,
write the code to process the serial output and display etc..

I did not use a hobby aluminum case, I custom built one with no gaps
(motherboard has a temperature sensor so I could check this for
possible overheating) and this was grounded. Without hooking up the
data aquisition card and just powering up the EPIA M in the seperate
aluminum case with no connections of any kind to the airplane I get the
interference in the radio. There are no connections coming out of the
aluminum box except for power and this line has caps on it for
filtering.

So it is coming solely from the motherboard, some chip on the board is
oscillating in the 107~130 Mhz range, given this occurs against one
home computer running at 2Ghz, another at 2.4 Ghz and the EPIA and 500
Mhz I would guess it is some supporting chip, but even if I knew I am
not sure that would do me much good. Perhaps changing the aluminum case
to a different size/shape would catch the offending frequency but I am
in the dark here and would be shooting in the dark.

There only seems two generic routes,
A) find a small computer which does not emit these frequencies (but I
do not know what is emmiting them so I would not know which computer
choice would alleviate this)
B) Some vastly better shielding approach for the motherboard.

Ideas?

Thanks



Bob wrote:
The "noise" could be coming through the connector and could be
emitting
from the wires.

Try using a connector with a metal housing and backshell and wires
with
shields, terminate the shields to the connector backshell/housing
which
will ground to the chassis.

The other end of the wires, try to terminate their shields where they
connect to.

Aircraft environment is not the same as home environment. Different
applications different techniques.

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