Sonar issues

[BobT]

I have a Hummingbird 596c HD DI on my console. Transducer is mounted on the stern to the right of my outboard. Has been in this location since I installed the unit a few years ago. Until this spring it has worked great, although I may sometimes lose bottom at high speed.

I have two different problems and based on my testing, I do not believe they are related but it sure is a coincidence that they both appeared simultaneously.

 

Problem 1 : Erratic depth readings. 
I have not had this problem until this spring. It seems to be having difficulty determining the depth. The image displayed on screen is definitely showing a bottom but if I watch the digital readout I’ll see it jump to high numbers repeatedly. For example, I can see the sonar graphic showing that bottom is only 3’ down but watching the digital readout I can see numbers flash as high as 60’, 70’, 80’ or just about anything. As a result the automatic depth scaling is bouncing around causing my graphic image to bounce from top to bottom on my screen as the scale changes. This is not only a problem in shallow water but at all depths. Sometimes it settles down and works for a while and then starts up again. 

I had not changed any of my settings prior to this beginning to happen. Since experiencing the problem I have been trying everything I can think of. Adjusting sensitivity, surface clutter, electronic filters, and so forth. I can work around this to some degree by setting the depth scale manually but that is a bit of a pain.

This problem exists even before turning on my electric trolling motor, other sonar units, livewell pumps, bilge pumps, etc., but it also continues to persist even after turning these things on. 

Problem 2 : Interference.
This spring I replaced my bow mount trolling motor with a MotorGuide Xi3 with Pinpoint GPS. Immediately when I plug in the power cord to the trolling motor, I begin to see interference on my Hummingbird 596c HD DI that appear as evenly spaced thin vertical lines and it is worse when the motor is actually running. Some of the things I’ve done to help are as follows.

• In traditional view, I use my 200kHz 25° transducer instead of the 455kHz 16° cone. If I use the narrower beam the interference is too much. 
• In down imaging view, I use my 455kHz 75° transducer instead of the 800kHz 45° cone. Again, the narrower beam captures too much interference.
• Reducing my sensitivity helps but I’m concerned that I am also filtering return echoes from fish as a result. 
• It also helps to use Switchfire® clear mode instead of max mode. In max mode it is much worse and again I’m concerned about reducing the unit’s ability to display fish arches.
• It helps to lower the surface clutter as much as possible, which again is obviously filtering out some return echoes but hopefully from smaller fish.
• I tried all the various filter settings with High 1 seeming to be the best but still not great.
• I have added ferrite core filters to the power cable and transducer cable.
• My trolling motor battery operates my trolling motor only and is located along side my console.
• My starter battery operates all other devices and it is located at the rear of my boat.
• I bonded the dc common on both batteries to each other and this helped a little. 
• I have verified that my boat hull is bonded to my battery commons.
• I have not been using my bow mounted sonar unit so I know this is not involved….yet. 

While writing this, it occurs to me that there is another thing I can try. There is a four conductor cable that is wired to the bow of my boat. Two of those leads are routed back to my trolling motor battery for supplying the trolling motor and the other two leads are connected to my starter battery for supplying my bow mounted sonar unit. What this means is that for at least part of their runs, they are connected parallel to each other and I suppose it is possible they are inducing signals on each other. I can try disconnecting the part that is connected to my starter battery, since I haven’t been using my front sonar and see if this does anything.

I’m running out of ideas. Any suggestions short of replacing components? 
 

[Jim Almquist]

Sorta sounds like a bad transducer but the interference problem makes me think that there is something else going on. Have you or can you do a hard reset on the unit ?

The one other thing that I would try is to disconnect everything from the battery that it use's and see if any of the problems clear up.

If the unit sits in the sun put a damp towel on it to cool it down and see if it acts any different.

[brrrr]

i have a 597 DI combo and have experienced many of the same issue.  I rarely see interference from the TM though.  the losing depth has been an reoccurring issue. on Sunday i was in about 11 ft and it was reading over 600' at idle and trolling speed.   

I've always had a problem with this unit losing bottom at speeds over about 25 mph, I've adjust the transducer location with some improvement but due to the unreliability of this unit I now only use it for DI, i have a helix g2 unit that i use for 2d and maps/ navigation.  

you can try manually setting the depth range instead of using auto, that seems to help.  however I think the transducer is either not getting a good connection to the head unit or is failing internally.  I've read that these transducers (XNT 9 DI  T) have had issues from the beginning.  I've been reluctant to replace my transducer as I'm not sure it will help.  

  

[BobT]

1 hour ago, Jim Almquist said:

Sorta sounds like a bad transducer but the interference problem makes me think that there is something else going on. Have you or can you do a hard reset on the unit ?

The one other thing that I would try is to disconnect everything from the battery that it use's and see if any of the problems clear up.

If the unit sits in the sun put a damp towel on it to cool it down and see if it acts any different.

Thanks for the reply. I neglected to mention that I did try resetting to factory defaults and all that did was make me have to start all over adjusting again. Didn't help otherwise. 

It uses the starting battery. I am going to try and disconnect that pair of leads that are routed up to my bow for my front mounted sonar unit because they are part of a 4-conductor wire that splits off about half way up there. From my own personal electrical design experience I am aware of how wires in parallel will induce voltages upon each other. 

The problems persist right from first launch until I return so I don't think temperature is a factor. I've used it on much hotter days without issue before. Good suggestion. 

[BobT]

1 hour ago, brrrr said:

i have a 597 DI combo and have experienced many of the same issue.  I rarely see interference from the TM though.  the losing depth has been an reoccurring issue. on Sunday i was in about 11 ft and it was reading over 600' at idle and trolling speed.   

I've always had a problem with this unit losing bottom at speeds over about 25 mph, I've adjust the transducer location with some improvement but due to the unreliability of this unit I now only use it for DI, i have a helix g2 unit that i use for 2d and maps/ navigation.  

you can try manually setting the depth range instead of using auto, that seems to help.  however I think the transducer is either not getting a good connection to the head unit or is failing internally.  I've read that these transducers (XNT 9 DI  T) have had issues from the beginning.  I've been reluctant to replace my transducer as I'm not sure it will help.  

  

Something else that occurred to me today. I need to test this to be sure but if my memory is still correct I don't think I experienced the interference unless the TM was actually deployed in the water. When we pulled it out to move to new locations, I believe the screens cleared up. 

I might also try disconnecting the GPS module so it is not functional and then see if things are better. Maybe I can isolate it that way if the GPS is actually the source of the interference.

[BobT]

I was doing a little more testing yesterday evening. I disconnected the wires leading from my starting battery to the bow of my boat and then deployed and turned on the TM to see if I got interference on my console's sonar unit. I did this at home so my TM was not in water, whether that matters or not, I'm not sure yet. Applying power to the TM did not create any interference but immediately when the motor moved I could see interference. Every time I started and stopped the motor I could see it. I'm guessing that the motor is controlled by some kind of pulse generator and that signal being on and off is probably what is causing the vertical lines on my graph. I didn't want to run it too much without it being in the lake but I saw enough to see the noise. 

Thinking on this more today I'm going to try another thing for fun. I'm going to get my Vexilar battery and power the Hummingbird with its own completely isolated power supply. Even though it is now powered by a different battery from my TM, I'm sure there could still be some crossover possibly in part through the on-board battery charger. It'll be interesting to see if this works. 

Edited May 30, 2018 by BobT

[BobT]

It's beginning to look like I may have isolated the problem. Today, I took my Vexilar battery and powered my Hummingbird off that battery so it was completely isolated from the rest of my boat batteries and I was not able to see any interference here in my shed. I reconnected my HB to my starting battery and the interference was immediately apparent again when I started and stopped my TM. I'm anxious now to try it on the water with the HB on its own power supply. I'm feeling pretty positive it will work now. 

[Surface Tension]

 I've been in the same boat. You can try the ferrite choke on your power cables, take the loops out of your ducer cable, use a dedicated battery for the sonar but grounding the trolling motor at the skeg to your sonar's negative power cable is usually the fix that works.

[BobT]

3 hours ago, Surface Tension said:

 I've been in the same boat. You can try the ferrite choke on your power cables, take the loops out of your ducer cable, use a dedicated battery for the sonar but grounding the trolling motor at the skeg to your sonar's negative power cable is usually the fix that works.

Grounding the TM. Drilling into the skeg to apply a ground tap would void the warranty on this new unit. It would seem they would already be doing this internally. Why they don't is a good question.  I'm sure the motor housing is threaded to the shaft so it's too bad there wasn't some way to fasten a ground strap on the inside of the motor housing and then run the wire up to the top and make the connection internally. The power wires are crimped together inside the top head of the unit so it wouldn't be hard to make the connection there. Having another wire dangling on the outside of the motor is not appealing.

Edited May 31, 2018 by BobT

[BobT]

One more test tonight. Disconnected the on-board charger from my TM battery so it was totally isolated. Still got the noise on my HB. 

Hope to try it on the water this weekend with my HB on it's own power source to prove it out.

[BobT]

I finally figured it out, although it kind of sucks in a way.

I mentioned earlier that there is a 4-conductor wire that supplies the bow of my boat. These are large wires and two of the wires branch off to my deep-cycle battery that is located next to my console for powering my TM and the other two run all the way back to my starting battery in the rear of the boat.

I was using the two wires from the starting battery to provide power for my bow mounted sonar unit (Lowrance x67c). Apparently, the TM uses a pulse modulation or something similar and when it is running I believe it induces a voltage on the two wires that connect to my starting battery. When I disconnect those two wires from my starting battery, my HB sonar on my console cleared up and is working well again. Unfortunately, this means that I no longer have power at the bow of my boat for my x67c unless I connect to the wires from my deep-cycle battery which are supplying my TM. I'm sure that will still induce noise on my x67c.

In reality I don't use the x67c very much up there so I decided to just remove it altogether and eliminate the hassle of the transducer cable hanging on my TM. I use the x67c in my winter pack so it still has a purpose. 

Another thing I discovered is that the noise is also carried by my on-board charger so if the power cable for my HB comes anywhere near the charger's cables, it will pick up the noise again. 

Edited June 4, 2018 by BobT

[Surface Tension]

If I follow you correctly, you were using a pair from the 4 conductor intended for a 24v trolling motor.

 Normally you'd tap into the bow light to power your X67c in the bow and you can still do that.

As to the earlier reply, I can't speak for MotorGuide but Minn Kota does address interference with the grounding wire run internally on their newer trolling motors.

[BobT]

On 6/6/2018 at 5:53 AM, Surface Tension said:

If I follow you correctly, you were using a pair from the 4 conductor intended for a 24v trolling motor.

 Normally you'd tap into the bow light to power your X67c in the bow and you can still do that.

As to the earlier reply, I can't speak for MotorGuide but Minn Kota does address interference with the grounding wire run internally on their newer trolling motors.

My boat was not equipped with a bow interior light from new. I added one by powering it with the same pair I used to power the front fish finder but since I have disconnected that pair from the starting battery, I no longer can use my bow interior light. 

I suppose I could tap into the bow navigation light but that would require running my console lights all the time and putting excessive drain on my starting battery unnecessarily. It's working well now and since I decided to remove the X67c from the boat I could tap into the navigation light to supply my interior light since both are only used after dark. 

[delcecchi]

As an Electronic Engineer with many years of experience, I would agree that you seem to be picking up noise from the pulse width modulation used as a speed control in modern trolling motors.   It also seems like Motorguide didn't do a good job of controlling the switching speed to limit the coupling and interference.   I wonder what the FCC testing on that motor showed.   

Humminbird also saved a buck or two on filters on the incoming power.   For what they charge they could have put in a filter on the power line (typically a couple of capacitors and an inductor)

External filters are also a possibility.  Car Audio guys are into those.

https://www.amazon.com/Axxess-AX-ANR1000-Inline-Power-Filter/dp/B0049MWUMQ/ref=sr_1_12?ie=UTF8&qid=1528945304&sr=8-12&keywords=power+line+filter+automotive

https://www.amazon.com/Pro-Trucker-Radio-Common-Filter/dp/B01MU7ONLT/ref=sr_1_2?ie=UTF8&qid=1528945437&sr=8-2&keywords=power+line+filter+automotive