Interference - GPSMap 8412 + GT56 + MK Riptide Terrova

[Scottfromoz]

G'day all,

I find my GPSMap 8412 gets bad interference from the Minn Kota Terova Riptide trolling motor (a 2017 BT model) when it is being used – this is in the way of bands across the screen separated by about 1cm on sidevu. This does not occur on the Echomap SV 95 Plus which runs from the same power distribution fuse board. The Minn Kota runs from its own battery in the bow of the boat (the bow battery). The bow battery is grounded back to the start battery (that the Echomap and GPSMap run from) and the positive from the bow battery runs to position 2 on a Blue Seas dual battery switch. As such when I have the sounders running on position 1 from the dual battery switch there is no current running through the switch from the bow battery and there should be no interference with the sounders (and as I say the Echomap doesn’t have any interference). Unfortunately this makes the 8412 sidevu unusable when the trolling motor is operational (which is often).

I wonder if the GT56 on the 8412 is more sensitive to interference than the GT52HW on the Echomap (and whether this is in part due to the 1070 v 800khz difference between the two). So I switched to 455khz on the GPSMap and still had significant interference. I don’t want to crank up the noise reject settings on the 8412 as it will likely remove some of the data that I need to see and the interference is so significant I doubt it would remove it entirely anyway.

I have read that the fuse in the head of the MK can blow (but again, if this were the case I would expect to see some interference at least on the Echomap). I will try disconnecting the leads from the bow battery that run to the crank battery and dual battery switch and see if that sorts it out (there may be some feedback of some sort coming along the leads even when the switch is isolating the bow battery as a power source to the sounders).

Any ideas would be appreciated.

[DR. DROP]

Is the GT56 transducer cable separated-away from the power cable on the trolling motor?

[Scottfromoz]

Dr. Drop, yes mate. It does run near the dual battery switch but that switch stays on position 1 which means the sounder is using the battery in the stern and the battery in the bow that the MK runs off is isolated (but the positive wire from the battery in the bow (which joins at the post with the MK positive lead) runs to the same switch (position 2). If the leads from the MK battery in the bow are causing the issue by setting up some interference along the (closed) circuit to the dual battery switch and crank battery in the stern, the GT56 must be more susceptible to interference given the GT52 doesn't have that issue.

Cheers

[DR. DROP]

Is the GT 56 mounted on the trolling motor?

[Scottfromoz]

No mate, the GT56 is mounted on the transom. Cheers

[jm_middleton07]

I started with a echomap 93sv uhd on the front and a lowrance unit at the console. I never had any issues. When I changed out the console unit for the echomap 73sv uhd I started having issues. I noticed I had a lot more clutter/interference on the 2D sonar screen. I finally realized it was the console unit interfering. I now turn off the console unit off or disable the sonar. Both of my units have the gt54 transducer. I tried changing frequencies but it still didn't get as clear as what it was with one turned off.