homemade EFIS system and EMI

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)

Physically separate the offender from the victim, especially the point of
entry of the signals into the victim. Don't forget about coax cables, comm
antenna and things like that, not just the radio box. You could try
reorienting the motherboard 90 degrees in various axis.

This is without the system connected to any of the sensors, just
turning it on and with an external battery so it is physically isolated
but within 6' or so it causes interference. Rotating the motherboard
does not help either. Thanks for the reply.

"jcpearce" wrote in message oups.com...
This is without the system connected to any of the sensors, just
turning it on and with an external battery so it is physically isolated
but within 6' or so it causes interference. Rotating the motherboard
does not help either. Thanks for the reply.


I have the same problems with my desktop machine and handheld radio...Wrap with aluminum foil and see what happens...

jcpearce wrote:

This is without the system connected to any of the sensors, just
turning it on and with an external battery so it is physically
isolatedseparateithin 6' or so it causes interference. Rotating the
motherboard
does not help either. Thanks for the reply.

Possibly try remotely mounting it back in the fusilage and running
fiberoptic to it. You can get inexpensive hobby FO and FO to rs232 modules
designed for experimenting.
Other than that try a non-aluminum case and use feed thru caps on all leads
and ferrite beads also. try some additional filtering on the PS and/or try
using separate PS for processor.
Just some thoughts.
John

ps those hobby aluminum cases do lousy for rfi prevention!