Thread: Isolating RFI noise

If you not bs me and you are having EMI problems after what you have already done, try installing a ferrite bead near as possible to the sonar head unit. You can git 'em (ferrite) at radio shack.

http://leadertechinc.com/ferrishield...Fdpb2godETPp0Q

I don't know if Humminbird sells their big "donut" filter separate for other applications. But, it works good to reduce the TM noise. i would guess that it is a toroidal ferrite coil wound for ground and power leads.

Last resort. Run a separate ground wire from the TM case to the TM battery negative. Try this, even with separate battery for electronics. May be big EMI via metal boat. Metal boat ain't nothing but a big antenna. I hate to do this but it is sometimes necessary.