Garmin 106sv + GT54UHD sidescan 1100kHz INTERFERENCE w Minn Kota Terrova 80lb 24V

[whoislang]

Hi,

Preface is that I am new to this forum but not new to saltwater fishing, boats, marine electronics. I am an engineer for an automobile mfg OEM and previously spent years building luxury sportfishing boats. (thanks for having me. looking to learn alot from the bass world, as yall seem to be more in touch with the world of sonar technology, MFDs and lots of gear-driven discussions happening here.)

Minn Kota Terrova 24v
12v50ah lithium in series
Garmin 106sv
Gt56UHD, transom mount

Interference is worst at certain speeds on the Terrova. Seems like its bad on ramp-up and mid range. Sortof goes away if I put it on 10. When the troller is off it is crystal clear.

I also notice it only occurs when I am using 1070khz chirp on the transducer. 810 and 455 don't have any interference. I do have the small ferrite ring installed around the ducer wire just before the plug on the MFD, as the instructions state this should reduce any interference. I have also wrapped the transducer wire off the transom in EMF tape, and a ferrite bead is installed at the transducer as well. All other sonar functions work well.

Quick google shows interference is mostly caused by EMF coming from the troller setup, I guess it is somehow radiating from the bow area. The house and trolling are completely independent systems. I can walk anyone through my rigging or boat if they have any explicit interest or want me to chase any leads.

Does anyone know how to best reduce the interference coming from the trolling motor? Can I set up anything differently or install something to make this go away?

Video below to show what it is that I am facing.

[rid 05 198]

So your house battery is the starting battery? If so, what size, type? Checks out? I noticed it read 12.2 volts on the unit and when you started the motor it went up to 12.4 volts. Mine when running it goes over 13v. ? ....Radiating from the remote? I have foot control.?

[whoislang]

House/Starting is a single odyssey AGM.

Engine is a yamaha 90 2s so likely not the best alternator but what I understand is that if the MFD gets at least 12v it will rectify whatever voltage it receives and run the transducer.

[BobKlindworth]

Does the trolling motor have a built-in transducer? If so, is it connected at all to your sonar unit (ie connected even if not selected)? If yes to both, consider disconnecting the built-in sonar.

If your sonar’s transducer is located near the trolling motor head, this can also result in greater RF noise.

Are there any wires (either power or transducer) that are bundled as a coil or loop? If it is possible to shorten them rather than cooling them, consider doing so.

Is there a way to further maximize the distance between all connected wires coming from
your trolling motor and all connected wires (power, transducer) to your sonar units? If they must be close, try to make sure trolling motor wires are not parallel to the sonar wires.

The perceived dependence on the trolling motor speed makes me think there may be some sort of RF resonance. This may be mitigated by changing the physical dimensions of the wires (shorter wires, perpendicular vs. parallel, or eliminating coils which can act like an AM radio antenna!).

Just a few things to think about.

[whoislang]

Does the trolling motor have a built-in transducer? NO If so, is it connected at all to your sonar unit (ie connected even if not selected)? If yes to both, consider disconnecting the built-in sonar. NO, considering irrelevant

If your sonar’s transducer is located near the trolling motor head, this can also result in greater RF noise The transducer is a transom mount. Please re read the OP

Are there any wires (either power or transducer) that are bundled as a coil or loop? If it is possible to shorten them rather than cooling them, consider doing so. I will check this inside the console but there is not a good way to shorten transducer wires or other Garmin multi-pin wires that I know of. What suggestions here?

Is there a way to further maximize the distance between all connected wires coming from
your trolling motor and all connected wires (power, transducer) to your sonar units? If they must be close, try to make sure trolling motor wires are not parallel to the sonar wires. The entire trolling system (batteries, plugs, wiring, motor itself) are 7-10 feet from the console.

The perceived dependence on the trolling motor speed makes me think there may be some sort of RF resonance. This may be mitigated by changing the physical dimensions of the wires (shorter wires, perpendicular vs. parallel, or eliminating coils which can act like an AM radio antenna!). What do I do with extra wire that would instead be just bundled up on the floor of the console? Much time was spent rigging this sytem as cleanly as possible to avoid clutter. Im not sure I can shorten the garmin specific wires with multi pin plugs on the ends without damaging things.

Just a few things to think about.

Langdon

[whoislang]

So your house battery is the starting battery? If so, what size, type? Checks out? I noticed it read 12.2 volts on the unit and when you started the motor it went up to 12.4 volts. Mine when running it goes over 13v. ? ....Radiating from the remote? I have foot control.?

What do you mean radiating from the remote? I assume the remote only outputs a RF signal to the motor when you depress a button? Watch the video, it is constant as the troller itself is working, not related to the remote.

[BobKlindworth]

Right, you probably can’t practicably shorten the transducer cable, but it is likely to be the entry point for the RF noise you are experiencing. It is less likely to be arising from the sonar power cable since the sonar unit has a regulated internal power supply unit which would likely filter out of the noise it receives.

To verify the transducer cable as the culprit, try rotating the orientation of any coil of cable you might have while the trolling motor is running to see if there is a noticeable change in RF noise on your screen. If not, it may be entering your system from another “antenna”.

[whoislang]

Sounds good.

But what is the actual source of the RF?? I have been told by Garmin it could just be the speed at which the prop rotates matches perfectly with the sonar? Causing interferenece? I would like to beleive that a prop rotaxting int he water wouldnt cause electromagnetic field or create radio frequencies.... but further fetched things have been true.

Any experts here? What gives?

Pretty lame that I cant use the setup as intended (garmin sidescan on highest freq setting + MK terrova) As I bought it for more of a search and destroy type fishing tactic.... Surely people on here or elsewhere are using this identical setup with success.

[BobKlindworth]

Any time you have an oscillation in the electromagnetic field, it produces electromagnetic radiation. In this case, the radiation is serving as noise to the electrical signal that your transducer cable is carrying to your sonar unit. The frequency of the noise doesn’t have to match the sonar frequency to cause a degradation in the electrical signal.

The ultimate source is indeed your trolling motor. That’s established by your video. The rotation of the motor armature within the field produces a back EMF (electromotive force, ie voltage) that oscillates within the power source. That source of RF radiation is typically reduced by isolation from the power source, but it won’t be eliminated completely.

If the motor is not brushless, there is also the possibility of a bit of arcing/sparking at the contact points in the motor. Even if the motor is brushless (ie Terrova Quest), there is EM noise produced by the rotation of the armature magnets within the field of the windings. A really cleanly-built motor will lower the EM noise, but it can’t be eliminated entirely.

Since you can’t live in a noise-free environment, we have to reduce the degree to which we pick up the noise. In other words, we need to reduce the effectiveness of the transducer cable as an antenna. The ferrite bead you used reduces noise by having the noise signal cancel itself out. The noise can also be filtered out by the sonar unit using Noise Reject/Interference settings (which I assumed you had already tried). Using the Noise Reject will reduce your signal strength and fidelity a bit, but it is preferable to a stronger noisy signal.

(By the way, I am a physicist, but wouldn’t call myself an expert. An expert would be an electrical engineer, and I think there is at least one of those that frequents this forum.)

[whoislang]

Thanks. Helpful insight.

Also I went as far as wrapping the ducer wire in "faraday tape" which I guess was supposed to act like an extra sheilding. This tape was added only on the area of the transducer that was exposed behind the transom below the waterline, as I figured the signal was traveling primarily through the water. The interference doesn't show up on the screen if I run the motor while the boat is in my driveway on the trailer. Tells me the signal isnt transmitted through the air.

Also I would assume that the sheilding on the wire as it comes from the manufacturer should be designed to be adequate enough to dispel any incoming noise or EMF? AM I wrong here?

[BobKlindworth]

Oooh! That observation makes me think of another suggestion. If you ground the housing of the lower unit of your trolling motor, you may be able to use the housing as shielding, shunting the RF noise to ground.

Weird that the size of the noise is affected by the trolling motor being in the water. My guess is that the amplitude of the noise is different when the motor is under higher loads (eg. while operating in water) rather than having a different material the RF noise is propagating through. I could be wrong though.

[Matt_Fisherman]

https://www.thehulltruth.com/marine-...erference.html

[whoislang]

Oooh! That observation makes me think of another suggestion. If you ground the housing of the lower unit of your trolling motor, you may be able to use the housing as shielding, shunting the RF noise to ground.

Weird that the size of the noise is affected by the trolling motor being in the water. My guess is that the amplitude of the noise is different when the motor is under higher loads (eg. while operating in water) rather than having a different material the RF noise is propagating through. I could be wrong though.

I am going to try to ground the motor housing when I get a chance. I’ll test with alligator clips like some other people suggested to try to chase my best option before screwing into the skeg.

I did a search earlier today and seems like there are 80 posts with similar problems but no 1 specific solution. You made a comment about my extra transducer wire being coiled. There are other posts that suggest not to coil it, instead to “figure 8” the extra. I’ll try that first. But like I said, gotta get on the water to see the effect.

[rid 05 198]

Try a different transducer?

[JK9027]

Since nobody has said it....check the fuse in the head plus try it without battery charger wires connected. If that fuse is good it should show continuity from neg side of plug to tm prop shaft...just saying

[EdCas]

The only thing that eliminated interference for me was disconnecting the onboard charger from the starting battery.
Trolling motor noise was finding its way into my electronics via the 3 bank charger.
I have my charger leads on wing nuts so I just disconnect the leads in the morning.

[Dennis S.]

The only thing that eliminated interference for me was disconnecting the onboard charger from the starting battery.
Trolling motor noise was finding its way into my electronics via the 3 bank charger.
I have my charger leads on wing nuts so I just disconnect the leads in the morning.

Great advice. I have my charger on leads with a plug and unplug after I charge the batteries. But my whole battery set up are lithiums.

[whoislang]

There is no onboard charger.

the trolling motor is a terrova saltwater. There is no fuse in the head

[whoislang]

Well, unfortunately the breakthrough regarding the coiled transducer wire acting as an EMF antenna did not seem to be quite the breakthrough we expected.

I originally had the extra TD wire coiled like so:
coil.jpg
And attempted to "figure 8" it instead:
figure 8.jpg
Launched the boat yesterday hoping to have a clear Sidevu image while running the MK and unfortunately, no dice. Same as before. Still created a washed out image when I start the motor with the remote.

I went to a completely loose configuration of TD wire, just letting it fall wherever in my console, and still no change or visible effect on the screen. So Im at a loss for if the wire configuration has anything to do regarding picking up interference. But it was worth a shot.

Next step will be to rig some alligator clips and wire between the skeg of the TM and try to ground the motor housing to the TM battery negative terminal. If that doesnt work, ground it to the house/cranking negative that runs the garmin. If either of those works, I will more permanently rig the grounding wire through the shaft of the MK so its a clean installation.

Any further recommendations are still appreciated. I know Im not the only one affected by this as there are 80 other similar posts.

Langdon

[whoislang]

Also, I noticed I accidentally titled this thread [GT54 UHD transducer]

I want to be clear this is regarding the GT56 UHD transducer