Sonar Interference

[kernr]

Good Morning -

I am starting to troubleshoot a nagging sonar striping problem on our boat. Essentially I am getting some sort of interference on our displays when in the Sonar function. We have 4 Garmin GPSMAP 1242 Touch displays and a AIRMAR B744V transducer that measures speed, temperature, and depth. I will provide photos of the striping problem displayed the transducer both inboard and outboard in this thread. Basically the problem occurs randomly often when you least want to see it and then it goes away. It almost appears that another electrical device is turning on and then about 10 minutes later it turns off and every thing goes back to normal. It does not appear to be depth dependent.

The boat is a GB Europa built in 2008 and hull #50 called Serenity. Any thoughts on how to troubleshoot this problem would be appreciated. I also have a query into Garmin for the second time to see if they have any new suggestions. I have talked with a very knowledgeable person at AIRMAR and he is adamant it is an electrical interference (EMI) with a Garmin connection or wiring. He states that the AIRMAR cable coming from the transducer to another connection is robust and not a contributor to the problem we are seeing.

Thanks for any thoughts as always,
Bob

 

[Hippocampus]

Have you tried ferrites around all cables and wires anywhere nearby?

 

[kernr]

Sonar

Hippocampus -

No, not yet. I am a little bit dreading the task of trying to track where the cable actually goes. The AIRMAR person did mention ferrites and I can see they are fairly inexpensive so it is obviously an option. One of the difficulties here is it is an intermittent problem. I think I need to take a day and follow the transducer cable to determine what other cables may be nearby. Unlike some electrical problems I don't know if there is a way to use continuity checks to help in the cable tracking - possibly someone can advise is there is a method on a transducer cable.

Bob

 

[Larry M]

Is your depth finder dual frequency? I had a similar problem with our Simrad depth finder at the lower frequency when we were in deep water only. I never could figure it out. We also had a Furuno that didn’t have the problem.

 

[kernr]

Sonar

Larry M -

The AIRMAR B744V transducer is dual frequency (50HZ & 200HZ). I have often switched between frequencies when striping occurs and it makes no difference - i.e. striping remains present. Depth does not seem to be a difference maker either. I feel pretty confident that it is most likely a EMI problem and I will need to find where the transducer cable goes.

Thanks,
Bob

 

[Mac2]

A little more history is needed. Did you own the boat when the transducer was installed? Have you always had the problem, or did it just start? I'm wondering if you added electronics that caused the problem (AIS, VHF, etc).

 

[Larry M]

Bob: I’ve got 10-6mm (1/4”) ferrite chokes you’re welcome to for the cost of postage.

 

[kernr]

Sonar

Larry M -

Let me do a little more investigation and then I may take you up on your offer - Thank You!!

Bob

 

[Circumnavigator]

Everyone with a boat that has a wiring maze should have a wire tracer. Here's an example -- while Triplett is a good brand, I haven't used this one, so it's only an example, not necessarily recommended.
https://www.triplett.com/collection...ucts/3375-fox-hound-jr-compact-tone-probe-kit


The transmitter puts a distinctive tone on the wire and the receiver picks it up inductively. It will work on any two or more conductor cable, but generally you want the power to be off.


Ferrites on the depth sounder cable might help, but generally it's better to have them on the cable that is the source of the problem.


Can you trace the intermittent behavior? Does it come on when you turn something on? Try with everything off and adding things one at a time.


I suppose that it could be interference from a depth sounder on another boat -- that's a guess as I've never heard of it happening -- but that would account for intermittent behavior.


Jim

 

[kernr]

Sonar

Mac2 -

We purchased the boat in Feb 2020 right at the start of our country's COVID problems then had to get it out of FL to avoid sales tax and then in April brought her up to New England where she has been since then. So, the transducer is original 2008 equipment but the Garmin displays GPSMAP 1242 touch are probably 2015 vintage and not original - I do not know when Garmin started making them. I believe the problem has always been there just comes and goes in sort of a random fashion. but as you can imagine in doing the ICW or cruising the Bahamas we don't need to struggle seeing the bottom depth readings with this problem. i have not replaced any electronics but I have been working on pieces to get them to function correctly (e.g. getting AIS 600 to transmit own ship position and putting a NNMI into the DCS radio so it would work if needed. No real new equipment and problem has been there since 2020 - did not show up on sea trials - but did while transiting up from FL.

Bob

 

[kernr]

Sonar

Circumnavigator (Jim) -

It usually happens when we are all alone on a transit so not another boat. Thanks for the ideas on a wire tracer - I will pick one up and could come in handy. Since the boat is on the hard for the winter and the batteries are all disconnected I will have to wait until spring time to try to find the interference culprit. Also, I don't think it is a good idea to turn on transducer while not in water (I've read that somewhere).

Right now I think I will focus on tracing the cable and where it pins out to a Display box. It could be a pin out problem. Garmin has come back with a similar thought that it could be the wrong wire adapter block being used. I believe that box might be behind the lower helm displays. Need a 50F day to check it out - Admiral says not tomorrow!! I said yes Mam!! Happy Thanksgiving!!

Bob

 

[diver dave]

I have done quite a bit of EMC engineering. First step is to identify the culprit. Turn off everything else and note if its self-inflicted or external. Then start to slowly bring other systems on.

“Everything else” includes engines, all dc and ac devices.

 

[tpbrady]

Just for grins, disconnect the connector on each end (may not be one on the transducer end) and reseat them. Many intermittent problems like that are traced to loose or bad connectors.

Tom

 

[sailormike]

I am now having the same issues never had them before myself. We will have to trouble shoot together.

 

[Ka_sea_ta]

I suspect that the issue is not interference but a bad connection in the transducer cable or a failing transducer. To verify find another compatible xducer connect it to sounder and hang it overboard. Personally I'd clean the connections first. what happens when the sensitivity or gain is turned up?

 

[kernr]

Good Evening -

I hope everyone got there fill of turkey yesterday - I know I did.

So, an update because I have been tallking to Garmin Support online and I got to boat today (54F in RI) before it started raining. Basically the support folks asked how the transducer cables are connected to the Garmin display. I went to boat and removed the primary display from its seat and looked behind it. There were the transducer cables going into a wire block adapter to take the 8 pin transducer cables into the 12 pin connection on the display. There is a bright yellow label on the box saying, "DO NOT USE THIS ADAPTER WITH 8 PIN DIFFERENTIAL TRANSDUCERS." Since the AIRMAR B744V is an 8 pin transducer I am waiting to hear back from Garmin support as to what they recommend prior to opening up the box to check for loose connections.

Looking at all the other wires and their closeness I am not surprised at the interference problem. The photos show the wire nests onboard behind display and coming up from engine room. The final shot is the bundle in the engine room going up to the electrical panels above. I physical traced the transducer cable into that bundle. More to come I am sure.

Bob

 

[kernr]

Sonar

tpbrady -

Unfortunately the transducer does not have free ends that are loose at the transducer end. That's why a wire tracer is difficult to use from the transducer end. But I definitely know and see where the cable goes prior to entering Garmin display. So once Garmin support gets back to me I will take the cover off the adapter box and check out the connections. I think if the adapter box is okay and connections are tight I will have to figure out the power sources close to the transducer cable and probably use some ferrite pieces on suspected power cables.

Bob

 

[tpbrady]

Kernr,

I think it may have already been mentioned, but go pick up a cheap “telephone toner” on Amazon. You only need access to one end of a cable to put a tone on it, that can be heard with a handheld inductive amplifier with a probe on the end that is part of the kit. They are invaluable for finding a needle in a haystack if you can put a tone on it. Back when phones were not mobile, you could find a single wire out of 100 on a punch block pretty fast as well as trace the route of the cable that got it there from the jack.

Tom

 

[PNK]

sonar interference

Kernr,

Are you able to see your electric panel while you are looking at the sonar display? Typically AC motors create more interference than DC, so you can focus on those to begin, and see what is on or off when the interference happens, to narrow it down further, and avoid having to trace every wire on the boat.
I am not familiar with the Europa, but you probably have a number of motors that come on and off automatically, like pumps, heads, a/c, fridge, etc. Fan motors can also create such interference; there may be one or more in behind your display panel to keep the electronics cool.
Good luck, must be really annoying!
Peter

 

[kernr]

Sonar

PNK - Peter -

You are correct - it is annoying. Sometimes (not very often) it happens when you are entering a port where you have never been before. At that point I just slow down and hope the chart is correct. Should not have to deal with it.

Normally due to better visibility around the Europa we drive from the fly bridge. The electric panels (AC panel photo below) are at the Lower Helm - of course. But when it does happen it usually stays on for a good 10 to 15 minutes - enough time to drop down to lower helm to investigate. The one item you did mention was the fan. See photo of fan right behind the Garmin display in between it and the Wire adapter block that the sonar wires come into. Certainly a potential suspect. AC motors that could be cycling while underway are the Galley fridge and the Ice Maker.

When we cruise we are minimalist regarding power usage - usually no AC required in NE, heads (vacuum) usually shut off and a tight water system so no water pump cycling.

I will check connections in adapter box first and then take a look at fan / Ac loads when power is restored to boat. It shouldn't be that hard. More to come I am sure.

Thanks for your input,
Bob

 

[Bob M]

I've a sonar stiping problem on a new Lowrance FS MFD that I've been trying to fix for several months.



I've tried moving the transducer and cable, moving the MFD off the helm a few feet, and through warranty replacing the MFD and transducer. No luck so far.


In my case the stripping is always present at all frequencies and with both downscan and regular sonar display. The word always means always. It makes no difference if anything else is turned on or off, the striping is always there.


In addition to the transducer cable, there is a NEMA 2000 network cable attached to the MFD and a power cable. Switching the network off has no impact on the striping. Disconnecting the NEMA 2000 cable has no impact on the striping.


The MFD is mounted on the helm console and I've tested temporarily running the transducer cable to the MFD without running it through the mass of wires under the helm, no impact on striping.


If EMI is contaminating the transducer cable signal, I'm guessing it would have to be from a wire very close in proximity to the MFD. That's a very large collection of wires.



Does it make sense to attach a ferrite choke to the transducer cable itself, very close to where it connects to the MFD? The alternative seems to be to connect a ferrite choke to every power wire under the helm. That's a lot of wires.

 

[wkearney99]

Given how periodic it looks, and that it's repeatable, I'd be inclined to think it's the transducer itself. Which is difficult to troubleshoot as you can't easily swap it out.

As for power and other interference, I'd think about setting up temporary wiring that allowed you to power ONLY the barest of equipment necessary to demonstrate the problem.

If you can't easily separate out the transducer cable from the bundles, then running with EVERYTHING else turned off via breakers would be my next step. Doesn't really matter what else you're running alongside the cables if there's nothing active on them.

Because if rigging straight from batteries to the display, with nothing else running, doesn't eliminate the problem then you're left with the chips inside the transducer sending the signal, or the digitizer chips in the chartplotter that processes them.

I'd wonder if there's some other inexpensive way to plug that transducer signal into something else to see if the problem follows the transducer? Find out if there's something 'cheap' that can also handle that transducer input and give that a try? Second-hand via eBay comes to mind...

 

[Bob M]

A faulty transducer or MFD was my thought and the thought of Lowrance technical support; they replaced both the transducer and MFD, but that didn't fix the problem. BTW, with the exception of the striping, this MFD works as advertised. It's a Lowrance Elite FS.



With the exception of bringing a temporary battery onboard hooked only to the MFD, I don't think there is anything left to disconnect or turnoff on the boat that I haven't already turned off or disconnected.


Originally the transducer cable ran parallel with a cluster of power cables. The transducer cord is now isolated except at the helm. If there is interference from power cables or devices, it would logically be at the helm.


I did some reading and YouTube viewing last night about ferrite beads and rings. I've ordered both from Amazon. I'm going to try ferrite on the transducer cable close to the MFD. Unfortunately, I won't be able to test this possible solution or any other until the boat gets relaunched next spring.


Thank you for your response to my post, Bill.

 

[wkearney99]

I was responding more to kenr's original posts. There's some overlap as multiple members here are having similar issues. Much of the troubleshooting remains the same.. up to a point.

As to my reply, I was skeptical of assertions about what was or wasn't fully turned off. I have an EB47 and also run from the flybridge, so I know of the hassles of trying to debug something like this. Thus my suggestion of a direct connection of the batteries and a full disconnect at the breakers of EVERYTHING else (both AC and DC). Take out the power and ground loop connection of the DC voltage from the chart plotter by going direction to a battery. If everything else is truly 'off' then you're left with little more than the transducer itself.

Adding ferrites won't hurt anything other than make it a headache later when someone else comes along wonder WTF is going on with all these rusted iron chunks stuck around cables all over the place. For the most part if you've got things properly installed there's not going to be much need for added ferrites.

 

[kernr]

wkearney99 -

Thanks for the feedback and suggestions. I believe after I have satisfied myself that the connections from the transducer to the GPSMAP 1242 Touch Garmin display is totally understood and verified that I can move forward with isolation to try and find the electrical culprit causing the problem.

Right now I have traced to wires to a Wire Adapter Block made by Garmin that takes the 8 pin transducer wire and allows it to be "adapted" so that a cable can hook up to the back of the GPSMAP. There are two different sets of connections one for an AIRMAR B744V and another for the AIRMAR B744VL. Next time I go to boat I can measure the transducer plug to make sure I know which transducer is on our boat (No tag on the cable). Once that is done I will know for sure the correct connections.

After that I think I will await spring and wait to see if it occurs - if I change nothing I am sure it will. Remember it does not always happen and when it does then it is a 10 to 15 minute striping display. During that time period I can try to isolate problem child at lower helm.

More to come. Thanks for everyone's feedback,
Bob

 

[Bob M]

I've been focused on EMI, ElectroMagnetic Interference. Maybe the interference source is RFI, Radio Frequency Interference, maybe my cell phone. My cell phone is always with me on the boat, always powered on and could conceivably be the source of the always present sonar striping on the MFD.

 

[kernr]

Bob M -

I doubt if it is your cell phone but that can easily be eliminated by just turning it off.

I have now confirmed that the Wire Adapter Block connections between the AIRMAR transducer and the GPSMAP display are correct for the AIRMAR B744V (I verified the transducer by measuring the transducer plug - too short to be the B744VL) transducer. I will state that the help desk at AIRMAR is great. They always answer and are very knowledgeable about their products. BTW I asked them about their transducer cable and they clearly believe that their shielding would prevent any EMI problems. It sort of points me to the Wire Adapter Block getting affected by a power source close to it right behind the two GPSMAP displays at the lower helm. We will see.

Bob

 

[kernr]

Sonar striping

Hi All -

Okay, so the striping has now gotten worse with time and the frequency of appearance is more often. Sailor Mike - have you gotten anywhere with your striping problem? Let me know please.

I took wkearney99's advice today and went to the boat with an experiment in mind.
Basically I took the boat off shore power alongside the dock in 8-9 feet of water and shut down all AC loads - no AC loads running and the inverter was off. I then made sure there was only one DC load running and it was the Garmin GPSMAP 1242 Touch which also powers the AIRMAR B744V Transducer. The following display screen shots over 45 minutes show no change in striping.

I am beginning to believe I have a bad transducer / cable. The one thing I have not done yet is taken the connector off the back of the Garmin display and cleaned it up. I will do that this week and let everyone know what I find.

Bob

 

[wkearney99]

Sorry this has been such an on-going hassle for you. As you've narrowed down what it isn't you might be at a point where calling someone that's got a spare transducer or other gear might be able to do a few more troubleshooting steps. Some of the biggest money gets burned through having a tech debug everything that it ISN'T.

 

[hoplite808]

I see you've been focusing on the fault being in the hardware, but what about the software. Have you tried adjusting the settings in the sonar settings on the device? I had something similar and when I changed the settings to filter the surface interference stronger it mostly cleared up for me.