You can try increasing the squelch in the SV setup. I had to do this after installing LED landing lights. Went from 50% to 74% to get the noise to go away. Planning to install shielded wires at some point to quiet the noise back down.
If adjusting squelch helps, it might point to some similar noise that you can locate by turning things off (e.g. alternator).
RV-7A - Slider - N495KL - First flt 27 Jan 17
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