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post #1 of 5 Old 03-01-2008 Thread Starter
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Safe distance between compass and chartplotter


I am installing either a Simrad CX-34 or a Northstar M84 chartplotter on my 30' Lyle Hess cutter and I need some help figuring out what is a safe distance between the chartplotter and the compass. My compass is installed in the starboard aft end of the cabin.

I am planning to install the chartplotter on a RAM mount on the port side of the aft cabin, next to the companion way. I can then swing it into the companion way and view it from the cockpit. When the chartplotter is positioned in the companion way, it will be about 24 - 25 inches from the compass.

I am getting conflicting information about the chartplotters' compass safe distance from the chartplotter manuals and product information on the manufacturers Websites. Can anyone give me some feedback on what their actual experiences are on installing chartplotters near compasses?

The Simrad chartplotter should be okay because the manual says the safe distance is 25".

The Northstar plotter manual gives conflicting information. In one section of the manual, it says the display unit can be 4" from the compass. But in another section there is a caution that says all parts and cables must be 1 meter from the compass. Ugh!

I already bought the Simrad unit because I got a great deal on it, but I am now thinking of returning it and getting the Northstar unit. I really want to buy the Northstar chartplotter because it can interface with an AIS receiver and it has a higher resolution screen and its faster. But I am worried that it will interfere with the compass.

I would really appreciate any feedback on real world experiences on how close I can install the plotter without interfering with the compass.

Thanks a lot.
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post #2 of 5 Old 03-01-2008
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Once you make your purchase, you will find in the instructions of installation, that there are such requirements given. With my raymarine products the distance was mere inches, and when you see most helm arrangements, you see the same results. If the product you are buying is very sensitive, you might want to rethink your purchase.

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post #3 of 5 Old 03-01-2008
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My Furuno chartplotter is mounted at the helm, probably 8 to 10 inches above the compass. No problems at all.
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post #4 of 5 Old 03-01-2008
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Magnetic interference falls off with the square of the distance... most electronic equipment, with the possible exception of VHF and SSB radios, are usually safe at two feet or so. If the power leads are twisted, that will help shield them from interfering with the compass.

As always, if you have any doubts whatsoever... swing the compass roughly after the gear is installed to see if it has affected the compass. Chances are pretty good, with modern electronics, that at 24" it won't be an issue.


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post #5 of 5 Old 03-01-2008
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I dont think you will have a problem. Like Teshannons plotter, I installed my own C-80 Raymatine chartplotter and 4 instruments as well at the helm and ran the instrument Nav Pod units (Wind, Aoutohelm, Tridata, and Stero remote with I pod accessory cables) through a new bent pedestal gaurd. The closest the wiring came to the binnacle mounted compass was 18" and I did as Saildog advised..checked to see how the compass swung when hooked up, before final installation by doing a mock installation on the outside of the gaurd before doing all the final wiring and routing. I also shielded the wiring from chaffing through a small PVC conduit sleeve the whole length of the pedastal gaurd and all the openings in the stainless steel guard have rubber grommets around any of the edges.

Its amazing that three marine electronics installers in the area priced this job at anywhere from $1200 to $3000 quoting 9 to 15 hours to do this. Even though I had never done this before, with careful planning it only took me 4 hours. Go figure. The hardest part was drilling the 2 exit holes for the wiring through the stainless steel pedestal gaurd and for the 8 for the Nav Pod box bolts. I marked them out and took them to a machinist to drill straight without a drill press and something to hold the stainless tubes steady. That cost $50 for 10 holes.

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