My first Post... Is not a good one. - Interference

[rbarrow]

Maybe this can help understand the technology behind the interference. And have a better understanding of how to possibly fix it.

Trolling Motors with PWM (pulse width modulation) to control speed are notorious for this. Which many trolling motors use today, especially auto drive TM's.

You probably notice the noise goes completely or almost completely away when you have trolling motor at near max speed. This has to do with the duty cycle of the pulses to the motor.

PWM is nice for controlling speed because it is nice and smooth controlling speed and continuously variable from 0 to 100%. The down side is they put out Noise. PWM has been around forever and is used in many things. The designers of the circuit's know about the noise down fall of PWM and try to mitigate at the output by using various component's and designs. If any of these filtering component's have failed, it can cause very bad noise issues. And next to impossible to get rid of.

In the case of a trolling motor the PWM is being done at the speed controller board.
If it was me, I would start at the source of the noise, the controller. It is possible a filtering device has failed on the board. Faulty or worn brushes can cause the noise to be worse.

In my opinion, manufactures should start focusing on better filtering and or different design or this problem of sonar interference will just keep happening for many people.

Hope this helps!

This explanation is spot on....and is the only real solution for TM interference. While yes it is possible to have defective transducer shielding, it is almost ALWAYS an issue with the failed filtering components as described here. Running all the wires to this and that do absolutely nothing and in many cases make the situation worse.

Replacing components on the TM or even replacing the TM has been the only real solution.

Excellent post Brian!

Roy

[smitty010203]

Had kind of a break through last night. I took the boat out to do some fishing and as I got started I noticed something. MY INTERFERENCE WAS GONE!!! 100% clean...I couldn't believe it. Changing that armature really did make a difference.

BUT here is the thing. Whenever i would point my motor to the left, the interference would come back. And then at other times it would randomly come back. If I cut the motor then cut it back on it would sometimes clear the interference again. It was bizarre. I tried moving what cords around at the TM/Unit that I could to see if I could actually see a change in the interference but I could never get anything to happen.

So as some of you guys have said, I think being out on the water actually did make a difference. I am going to check it again in my garage today and see if it is still 100% interference like i did before (which would realllly confirm the need to be in the water for testing.). I will probably go ahead and try to run all my wires as cleanly as possible away from the TM wires before heading out as well.

I did notice my helm unit was picking up way more interference yesterday than it ever has as well for some reason which I thought was extremely odd. Regardless. I think I am still going to try and get away from Garmin.

[Skunked again]

How is getting away from Garmin going to help anything? They all have interference issues.
What about the gt-52 transducer? With dedicated DI.
One thing I've noticed, most every thread on interference, involves a digital trolling motor. Regardless of brand.
Have you tried mounting the transducer on a stick, away from the Trolling Motor?