Design Notes for Shielding and EMC issues

A project log for ModAir - Modular Aviation Instruments

Open Source Avionics for Microlights and other Non-Type-Certified Aircraft

reneRene 09/25/2018 at 07:021 Comment

The current avionic modules still cause interference on my VHF air-band radio. Whenever the power switch for the avionics is turned on, the radio intermittently shows the Rx light and plays channel noise. Turning the squelch all the way up reduces the issue to some extent. Unplugging the antenna on the radio stops the issue, leaving me to believe that I am dealing with radiated emissions from the avionics, rather than conducted emissions through the power supply.

Below are some design notes for the next hardware revision to mitigate the EMC issues:

The whip antenna position (in close proximity to the instrument pod) and limited ground plane (using the goose neck on the aluminium frame) are not ideal on my microlight trike. The aluminum frame structure and many stainless steel support wires make the antenna mounting challenging and distort the radiation pattern. I have not measured the VSWR, but expect quite a bad impedance match and significant reflections. If the next hardware revisions still cause interference issues, I will consider mounting a V or dipole antenna to the king post or the back of the keel.


garrick.smith wrote 11/08/2018 at 12:17 point

Rene - this is a commom problem we have had and it normally extends from power ancillaries such as USB etc Solution below worked really well to surpress, I have one installed

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