Shielded Wire for interferance

[FES313]

I am looking for shielded wire to run power to my front unit. I have always had some interference on my front graph since I got the boat new. I did not have an issue with the interference because it was just a spike that left a thin line top to bottom on the 2D screen when the trolling motor started. I just upgraded to HDS 9 GEN 3's and I put a total scan transducer on the trolling motor for the front unit. I still have the spike on the 2D but on down/side scan I have constant interference. Xpress in their infinite wisdom, ran all the electrical up the starboard side of my boat, including the wires for the trolling motor. I just got through trying a "great big jumper" away from the trolling motor wires and this cleared up my interference.

This brings my to my options;

1- Pull the existing wires for the graph and add shielding.

2- Buy shielded wire and rerun.

3- Drill through all of the compartments on the port side and reroute a set of wires.

Number 1 I could pull existing wires an add a braided copper sleeve for shielding. then that would have to go into a wire loom or such. It would be time consuming and tedious with all of the pulling and pushing trying to get everything to go together.

Number 2 would be the easiest but I am having trouble locating the proper stranded, shielded wire in 14 or 16 gauge. It seems all I'm finding is 20 gauge and smaller.

Number 3 is doable but time consuming. Which set to move, trolling motor or graph? Previous experience in tryin to remove a factory installed transducer found the whole wiring harness was zip tied tighter in multiple places which could add difficulty in removing trolling motor wires. I think I have most of the offending zip ties broke free.

Questions, comments, opposing view points, ideas?

UPDATE!


It worked! See my latest post

[jyu87]

I am running into the same problem. The interference isn't terrible but noticeable when you press down on the TM. It makes my graph a little lighter when viewing. Are you running into the same?

My cables are run through the trolling motor, I may try re-reouting and avoiding the head of the TM completely before anything else.

[CatFan]

Twist your wires. Twisted un-shielded will be be more noise resistant than straight shielded.

If you do go with shielded wire, be sure it is twisted as well. The wire is available, but you'll likely have to buy 50ft. Maybe you could sell the extra.

You'll probably get some people telling you to ground only one end, while others will tell you to ground both. Both ends grounded is best except in some cases where lightning is a major concern, but often there are issues when you are working with a system you don't design where adding the shielded wire COULD cause some issues with electrical noise. If that happens, try disconnecting one end of the shield.

[ntslam]

this is 14 ga. this would be perfect, unfortunately this is the largest ga. I could find of twisted and shielded

https://www.westmarine.com/buy/ancor...shield--542266

[FES313]

Twist your wires. Twisted un-shielded will be be more noise resistant than straight shielded.

If you do go with shielded wire, be sure it is twisted as well. The wire is available, but you'll likely have to buy 50ft. Maybe you could sell the extra.

You'll probably get some people telling you to ground only one end, while others will tell you to ground both. Both ends grounded is best except in some cases where lightning is a major concern, but often there are issues when you are working with a system you don't design where adding the shielded wire COULD cause some issues with electrical noise. If that happens, try disconnecting one end of the shield.

How tight of a twist? I did give the wires some twist when I pulled them, just enough to keep them together. Maybe 3 turns in a foot and a half.

[FES313]

this is 14 ga. this would be perfect, unfortunately this is the largest ga. I could find of twisted and shielded

https://www.westmarine.com/buy/ancor...shield--542266

Thanks. I didn't even think West Marine would have that.

[FES313]

I am running into the same problem. The interference isn't terrible but noticeable when you press down on the TM. It makes my graph a little lighter when viewing. Are you running into the same?

My cables are run through the trolling motor, I may try re-reouting and avoiding the head of the TM completely before anything else.

I'm getting "snow" on my down and side imaging screens. I can still see the bottom but the detail washes out.

[CatFan]

How tight of a twist? I did give the wires some twist when I pulled them, just enough to keep them together. Maybe 3 turns in a foot and a half.

More than that. More like one or two turns an inch. A drill makes it easy, and stop when it starts wanting to double over.

[FES313]

More than that. More like one or two turns an inch. A drill makes it easy, and stop when it starts wanting to double over.

Gotcha Thanks.

[suvowner]

if you have an onboard charger try removing the wires from all batteries and see if it clears up.

[Lou r Pitcher]

1st might confirm the objectionable interference path is indeed the power wiring...else the trouble you are pursuing will not be successful.

[Buzzsaw]

How about this:

https://www.prowireandcable.com/ib/belden-8718/8718/

[suvowner]

How about this:

https://www.prowireandcable.com/ib/belden-8718/8718/

that looks like it would be pretty good

[FES313]

1st might confirm the objectionable interference path is indeed the power wiring...else the trouble you are pursuing will not be successful.

Have already confirmed this. Check out the last sentence in my first paragraph in the op. Twisting the wires seem to have cleared it up some. I will get a day on the water soon and check it. We can only go up from here.

[Bass AHolic]

shielded wire is 1 option , click below for some more

https://www.boatingmag.com/how-to/se...s-interference

[Ann-Marie]

SHIELDING WILL NOT HELP

The reason your test showed good results was the independent connection to the battery. When instruments share a ground or power cable that is supplying other loads, especially a trolling motor, that load causes small noisy voltage drops along the length of the supply cable. If your instrument is powered off the end of this line it gets the interference directly from the power cable.

When you run a pair of wires back to the battery for the instrument that are not sharing the supply with any other items the noise is no longer directly connected to it. The low impedance of the battery filters noise coming from the motor so you get a clean supply for your instrument(s).

Shielding over the original cable will not help, all it will do is keep the noise inside the shield but that is where you are having problems in the first place.

[DougL58]

So how much power does a regular graph take? Say you are running a Helix 10 up front. What about a small battery placed up front just to power it. Isolated so no interference.

[CatFan]

SHIELDING WILL NOT HELP

The reason your test showed good results was the independent connection to the battery. When instruments share a ground or power cable that is supplying other loads, especially a trolling motor, that load causes small noisy voltage drops along the length of the supply cable. If your instrument is powered off the end of this line it gets the interference directly from the power cable.

When you run a pair of wires back to the battery for the instrument that are not sharing the supply with any other items the noise is no longer directly connected to it. The low impedance of the battery filters noise coming from the motor so you get a clean supply for your instrument(s).

Shielding over the original cable will not help, all it will do is keep the noise inside the shield but that is where you are having problems in the first place.

I think you misread the OP. Power wires are separate but run in proximity.

[jyu87]

Anyone have any pictures of how they are rigging their wiring for the transducer down the TM? Trying to isolate the wires as best as possible and avoiding the TM head. Trying to avoid all the extra slack. Any best practices, shoot them my way :)

[Bill Reynolds]

SHIELDING WILL NOT HELP

The reason your test showed good results was the independent connection to the battery. When instruments share a ground or power cable that is supplying other loads, especially a trolling motor, that load causes small noisy voltage drops along the length of the supply cable. If your instrument is powered off the end of this line it gets the interference directly from the power cable.

When you run a pair of wires back to the battery for the instrument that are not sharing the supply with any other items the noise is no longer directly connected to it. The low impedance of the battery filters noise coming from the motor so you get a clean supply for your instrument(s).

Shielding over the original cable will not help, all it will do is keep the noise inside the shield but that is where you are having problems in the first place.

I too am skeptical, because I have always associated sonar interference with RFI generated by the PWM motor controller at or near the trolling motor. Obviously, the circuit from the battery to the trolling motor controller is analog, so it would not be generating any RFI. What am I missing?