Lowrance Elite 7 HDI Electrical Sonar Noise

[Plyliteblue]

Hi,

I have recently purchased a Lowrance Elite 7 with a the 83/200/455/800kHz Transducer and am having issues with excessive noise present on sonar screen only when Main motor is running
Funny Thing is i have separated The unit from starting battery to a stand alone Deep cycle Battery with nothing attached to it and it still does it when i start the motor up I have put a couple of ferrite cores along the transducer cable as well as power cable to no avail.
There is some type of ambient electrical noise coming off main motor.Is there any easy way to source this interference?
Boat is a SURTEES 20ft Aluminum Fishing Boat Made here in New Zealand

Thanks

 

[gm280]

Okay by now I thought somebody would have chimed in and helped out. I'm sure after I give my .02 cents worth others will chime in and say differently... At least that's how it seem to work many times on here. First being how you only get the noise when the engine is running AND you have the unit completely separated from the other electric circuits via its own battery, then you have RFI noise. RFI is Radio Frequency Interference noise that is being transmitted from the engine itself. And that is probably from the ignition spark system I'm thinking. Without being there and troubleshooting the issue myself, you could try shielding the engine. Try putting some aluminum foil type material inside the cowling of the engine and see if that helps any. If it does, then I would suggest spraying some good adhesive on the inside of the engine cowling and layer some aluminum foil material all over the inside of the cowl to help eliminate the RFI. You could even look into some resistive type spark plugs as well. Other then that, make sure your transducer is away from the engine as far as possible to help also... Let us know if any of those suggestions helps. One other thing, make sure your Lowrance unit is NOT grounded to the aluminum boat at all. You could be picking up electrical noise via the boat hull ground as well. So make sure they are separated and not all grounded together... I'd make sure the engine isn't grounded to the boat hull as well...

 

[Barnacle_Bill]

Also check your transducer cable for any cuts and nicks. Those cables are completely shielded and should block and RFI. Another thing to try is replace your power wires going to it with a twisted pair. The tighter the twist the better.

 

[dingbat]

The first thing you need to do is isolate which "line" is picking up the interference.

With the motor running and interference on the screen disconnect the transducer cable. If the problem goes away, the interference is feeding back thru the transducer cable. If so, check for a damaged cable. Most Transducer cables are shielded with a drain wire and don't present a problem unless damaged.

Next step, disconnect power leads and connect, via jumper cables if need be, directly to a seperate battery. The idea here is to remove the power feed cable from the equation.

Next, make sure your using resister spark plugs and noise suppressed plug wires. If all else fails, put a voltmeter on the voltage regulator output and check for AC indicating a problem in the charging system.

What type of noise is it? Is the noise "rev" sensitive?

 

[Plyliteblue]

Thanks for the responses.
I am pretty sure the interference is RFI noise related as said by gm280.. .I can rule out Transducer because i have tried another transducer with no sign of change, this is with routing cable well out of the way of any electrical cables.I also have noise suppressed spark plugs.I am going to try the method of aluminum foil inside the cowing.@ dingbat No the noise is not rev sensitive.

 

[gm280]

Plyliteblue, after reading your last statement, if revving the engine doesn't change the noise seen on the locator, the ignition issue may not be your problem... Try the foil and get back to us anyway...

 

[dingbat]

Plyliteblue, after reading your last statement, if revving the engine doesn't change the noise seen on the locator, the ignition issue may not be your problem... Try the foil and get back to us anyway...

The aluminum foil idea is a waste of time and effort. Aluminum does not shield against EM or RF emissions. You would use copper or nickel foils..... Even if it somehow worked, which I doubt very seriously, you still have not identified the offending component....

We regress...does the interference subside when you unplug the transducer cable?
Have you wired the sounder directly into a power source not associated with the boat? A blown or weak dioide in the charging system will cause interference. It could be a problem in the power supply circuitry in the sounder itself but you will never known unless you systematically eliminate the possibilities.

Putting a tin foil hat on your boat isn't one of them...lol

 

[bruceb58]

I agree with Dingbat. Run the sounder off a completely separate battery to see how it works.

 

[NYBo]

I agree with Dingbat. Run the sounder off a completely separate battery to see how it works.

According to the first post, he has already done this.