Author Topic: Trolling Motor Induced Sonar Interference/Pulse Modulation speed control problem  (Read 4283 times)

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Offline offroad

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  • Unit(s): 1197/ 898
What a title and what a PAIN this problem is ....Now before l tell you my next move.... And l would like your opinion on, Let my tell you what l have done to try and cure it   Boat is a Skeeter SX170 Units are 1197/898.  On the console is the 1197 Bow 898 ethernet conected ,Two transducers one on the trolling motor other on the transon  Nothing else... Both have the latest sofware...Problem is when starting the trolling motor {Terrova 80lb } the screen on the 898  becomes unreadable and the 1197 is hard to read{ color is washed out } The wiring on the boat to the units and trolling motor have been separated each has its own path to its power source.The Terrova has the HB choke to the foot pedal And as HB suggested a earth wire runs from the skeg on the trolling motor to the neg side of the cranking battery also another negative runs from the Neg side of the 24volt trolling batterys to the neg side of the cranking battery .Data filters fitted to both sonar units power cables  Now l have found the problem ! its the transducer on the trolling motor.. As you move it away from the base of the motor the problem goes away.  So l have tried  different ways to form a barrier between the transducer and the motor base to no avail  So what about this Fiberglass the underneath of the motor base. Just a area big enough that covers the transducer so it forms a barrier..... your thoughs please


Offline mendota

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  • Unit(s): 1197
  • Software: 4.75
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Do you think the noise is related to TM vibration?  I would think wrapping some rubber, foam, etc around the TM before clamping the transducer on would solve that.

If it is electrically conducted noise, putting a thin, insulting sheet between the clamp and TM should effect the problem.  The path could be TM-clamp-transducer, or TM to transducer directly.

Are you sure both your sonars are running off the same source, and that it's not the TM batteries?

Make sure you have the newer shielded transducer on the TM.  The original 1197's were shipped w/o shielding on the transducer itself, so if you have radiated noise from the TM, only moving the tranducer away from the TM will solve the problem.  I believe all 898's have the upgraded transducer.

As an aside, I would never connect the 2 battery negatives - that is highly likely to be counterproductive.

Offline offroad

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Thankyou for your comments . Over the last few months l have tried many things to isolate the Trolling motor Transducer.... plastics, tape  even lead ! to no avail .The power source of both units is the cranking battery. As far as connecting the neg side of the battery's they do have a in line fuse and the setup was checked by a auto electrical person. The transducers are less than 12 months old.

Offline mendota

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I would check to be absolutely sure you have the shielded transducer, and that you have solid electrical connections for grounding the motor skeg to the battery.

A picture of your mount to the TM would be helpful to me.

Sounds like you are doing everything right otherwise.  I would still get rid of the common connection between the batteries.  Having your 1197 also effected is a bit of a mystery to me, because the implied interference path is TM-transducer-898 power to 1197 power, which is not reasonable or likely, especially in a glass boat.

I recommend you stop at your local Radio Shack and pick up 2 or 3 of their ferrite snap chokes, items 273-069 or 273-105.  Snap them on in various places (the transducer leads in particular) and note the result.

Offline offroad

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I recommend you stop at your local Radio Shack and pick up 2 or 3 of their ferrite snap chokes, items 273-069 or 273-105.  Snap them on in various places (the transducer leads in particular) and note the result.Now a caution! Some individuals have reported success with eliminating the interference by installing one or more of the Ferrite Data-line Filters also on the transducer cable. I would encourage anyone who reads this  NOT to take that step. I have no doubt that the filter will prevent the interference from being visible, but being a passive device it cannot distinguish between the unwanted noise (interference) and the desirable sonar signals on the transducer cable. It will attenuate all within its effective range by the same amount. This has the equivalent effect that the sonar in Automatic mode provides (e.g., reduced sensitivity). However, unlike the Automatic mode, it will cause the sonar to be unable to detect and display weaker echoes all of the time, not just when the interference is present. So - if you can live with the reduced sensitivity during periods of TM interference; don’t do any of the things discussed here; just operate in Automatic mode and let the sonar unit attempt to compensate       Have a read of this http://mysite.verizon.net/restmvit/tmintf.html


« Last Edit: May 27, 2011, 01:28:46 PM by offroad »

Offline offroad

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Now saying the above l don't wish to get anyone offside. You are all trying to help . l have a Boat Auto Electrician coming around today to try and give me some answers....Lets see if he has any !


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