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Old 24-11-2012, 19:18   #1
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EMI shielding??

Ok...heres the story...
Bought this great boat, see....and it didn't really have the best care taken of it , see...and it didn't have any electronics, see....
so...My beautiful wife and I decided to buy each other a Garmin 740s with HD radar bundle for early Christmas, see...(did I mentiopn yet how much I really love her?)
Anywho... back to it.
So got the chart plotter part in and powered up and it works great!!!! Did I mention how much I love my wife...of yeah, did.
So now I am trying to install the radar now...got all the stuff and goodies...and now figuring how to hoist my fat butt up the mast, as I can not subject her to that again...
So....
Im ready to start working...all the beer is in the cooler, got an extra pair of hands...and low and behold, it says that IF RUNNING ALONG SIDE OF OTHER WIRES, THAT IT SHOULD HAVE EMI SHIELDING SO IT DOESN'T GET INTERFERENCE????!!!!!!!!
WHAT THE ....???
Now, when calling West Marine (where my loving wife and I purchased it ...great deal by the way...and did I mention, yes , sorry, I did) they had no idea of this...and of course do not sell said item.
Also called an electronics store, and they had no idea what I was talking about...so I figure I was speaking Swahili or something ...so in my best English asked again, and still no dice.
So now...the $1.78 question...has anyone installed this themselves, and what did you do? Where did you get this 'EMI shielding' magic???
Or was a deal struck with the devil here, and someone installed it without this sorcery and what happened???
Did it all explode!???
Please...need to know ASAP as we sit in Half Moon Bay....trying to continue our great adventure.
Or if in the area...maybe stop by and point and snicker...we all know that helps too.
Thanks all!
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Old 24-11-2012, 20:14   #2
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Re: EMI shielding??

I'm not sure what type of wire your HD radar uses but most digital radar uses ethernet type wire. Such wire can be purchased with a shield or without. The shield is typically a layer of metal covered plastic (often mylar) or a copper braid. The plastic type usually has a small piece of stranded wire that runs along underneath and conducts away emi induced current. The cooper braid type is self conducting. In either case the "Shield" is attached to a ground connection at one end only. Attaching it at both ends of the wire produced a "ground loop" which you don't want.
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Old 24-11-2012, 21:12   #3
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Re: EMI shielding??

Thanks Capt Bill
The wire we are using is the Ethernet cable that came with the unit (Garmin 740s bundle)...no metallic tape or coating of any type...
It would be nice if they would tell you these things before you buy it all and start the install...now to have it all half done
So now...where to find this shielding in the San Francisco area!
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Old 24-11-2012, 21:35   #4
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Any electrical supply house will have it. Your looking for cat 5e shielded outdoor rated would be better. Bad on me I used the supplied cable on a mast mounted garmin hd unit. No way to separate the wiring from the other runs. Worked just fine. Excellent image.
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Old 24-11-2012, 21:38   #5
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Re: EMI shielding??

The metal shielding is under the plastic outer shell. Take an old piece of ethernet cable and strip it back, you will see what I mean. You really don't need to worry all that much about EM noise with ethernet cable.

In the SF Bay Area Fry's has it for the least amount retail that I know of. As far as internet prices go, check out MonoPrice.com.
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Old 24-11-2012, 21:59   #6
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Re: EMI shielding??

Thanks for the info folks! I called Frys today and they ( the sales people on the phone) had no idea what I was talking about.
I also read that VHF and HD radar are so far off that they will not interfere with each other...(or that we may never notice)
Also, I'd hate to peel the outer hard candy shell of the cable to get to the chewy center to see if its shielded...and I think that if it was... Garmin wouldn't say you need the shielding, right??
I also have been reading here as well as other forums on my search
( a good one on the trawlers forum) that many installs have just used whats in the box...and run it along side of everything else and no problems... Im still gonna check out the suggestions here to get the shielding, like go to Frys personally...and ask for the 5e stuff too)
I certainly can't afford the 700. I've seen for some of the 3m tape rolls...geez!)
and will just run the cable included if I come home empty handed...
now, for the help getting my fat butt up the mast to drill the holes...or someone lighter whos done it before...that might want dinner bought for them....hmmmmmmm?????
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Old 24-11-2012, 22:10   #7
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Re: EMI shielding??

Hi bp777 - I have an electronics background, but not specific experience with that particular unit. As per David M, it's my expectation that you won't have a problem if you use the supplied cables. If I remember I'll look for the manual online tomorrow.

In the meantime, you should tell your wife that you love her.
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Old 24-11-2012, 22:44   #8
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Re: EMI shielding??

I've got a Garmin 5200 chartplotter and a 18 Hd Radar with VHF and AIS and a Ubiquity Bullet M2 long distance wifi cable along with spreader and mast lighting. All mounted on the mast with all wiring sharing a single conduit.
Oh, also a HAM radio driving a cap shroud for antenna (none of that in the mast conduit).
No problem with any of it.

Someone's blowing smoke at you.
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Old 24-11-2012, 22:45   #9
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Re: EMI shielding??

You may are may not get away without a shielded cable, or you may find that you only have glitches at certain times (like running lights on, or spreader lights). Fry's does carry shielded CAT 5E and CAT 6 cable (I've bought it there), but the knowledge of their staff is not stellar.

FRYS.com*|*SHAXON

You probably don't want a 1000', but at least that should get them looking in the right place. Sometimes referred to as STP (Shielded Twisted Pair) [as opposed to standard Ethernet cable, which is UTP (Unshielded Twisted Pair)].

If you can't get it there you can try L-Com, IIRC their office is in Fremont so you might be able to pick it up. The sell just about every length as a patch cord, you could whack the ends off.

Shielded Ethernet Cable | Shielded Cat5e Cable | L-com.com

You could also try just about any industrial electrical supply house; Graybar, CED, Royal Wholesale, or even Grainger. Don't know which is most conveniently located close to you. The electrical supply houses will have outdoor/moisture rated cable that may be beneficial.
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Old 24-11-2012, 22:45   #10
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Re: EMI shielding??

Just a comment here because "the cheapest wire" was mentioned. Cheap wire is not what to look for in any marine application unless you enjoy failures when you need it the most and enjoy replacing the cheap wire with the correct wire.

Ask me why I know this.

I hope this helps.

Bill
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