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Old 25-05-2013, 15:45   #1
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Re-connecting Cut Radar Cable - Help Please

Hi all,

I know that this subject has been covered before, and I read as many threads about it as I could. However, I still have one question about the very small coax that is inside the radar (Furuno) cable. My cable has 18 separate wires inside, which are all being reattached using a long terminal block. That leaves one small (about 1/4-1/8") grey coax cable.

Now can I just separate the outside shielding and twist it into a wire, to be attached to the terminal strip? Then add a connector to the core wire and do the same thing? All the other wires are pretty easy.

BTW, I had to cut the cable to make the run inside my arch tube.

Thanks for any tips or insight.

Cheers, Bill
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Old 25-05-2013, 15:50   #2
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Re: Re-connecting Cut Radar Cable - Help Please

Not sure you are supposed to put the coax on a terminal board. Why a terminal board anyway?
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Old 25-05-2013, 16:18   #3
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Re: Re-connecting Cut Radar Cable - Help Please

Yes you can. The purpose of the outer braided covering is to shield the inner conductor from extranious signals that the inner cable may pick up on the airways. There is also a braided shielding cable for the whole group of wires. It looks as though you are commited so go for it. If it causes problems you may want to attach the small coax cable inner wire to a terminal strip of its own and mount it inside a small metal box that you have attached the braided cable to each end. This may give you the shielding integrity you need, same for the large one. Good luck, J.T. Duncan.
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Old 25-05-2013, 17:03   #4
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Re: Re-connecting Cut Radar Cable - Help Please

I recently installed a new Furuno 1715 on my mast and had the same issue. Called Furuno and they said to do just what you are proposing... it is done all the time with no problems (if you keep the terminal strip dry!).

I did so and have had no problems with the installation.

Cheers,

Jim
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Old 25-05-2013, 18:27   #5
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Re: Re-connecting Cut Radar Cable - Help Please

Quote:
Originally Posted by awpptdt View Post
Yes you can. The purpose of the outer braided covering is to shield the inner conductor from extranious signals that the inner cable may pick up on the airways. There is also a braided shielding cable for the whole group of wires. It looks as though you are commited so go for it. If it causes problems you may want to attach the small coax cable inner wire to a terminal strip of its own and mount it inside a small metal box that you have attached the braided cable to each end. This may give you the shielding integrity you need, same for the large one. Good luck, J.T. Duncan.
So something that is supposed to be shielded can be put out in the open with a bunch of other wires on an exposed tertminal board, or you need to build a grounded stainless steel box to put everything in, do I have that right? I know this is not the space shuttle but how about some realistic quality control. This might actually be a place for solder.
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Old 25-05-2013, 18:43   #6
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Re: Re-connecting Cut Radar Cable - Help Please

It's only a video signal. It's quite robust...not like an antenna signal. Should work to just separate the shield/screen and inner conductors onto adjacent terminals. Keep the separated portion short ... like a cm or two.

I've seen this cutting nonsense done several times. The logic was to save 20 minutes while pulling a mast at the expanse of ruining a nice cable and creating a maintenance nightmare in the bilge. Ugh. The better thing to do is cut the hole a tiny bit bigger and fish the small end thru ... usually the antenna end.
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Old 25-05-2013, 19:05   #7
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Re: Re-connecting Cut Radar Cable - Help Please

Thanks Guys! Now I don't have to ask. I'm in the process of re-rigging the masts and re-install in a couple weeks. I also had to cut my 50?meter cable at the mast base. I will use a terinal strip and put it into a clear Tupperware mounted to the wall. Easy to access just pulling the lid.
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Old 26-05-2013, 06:05   #8
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Re: Re-connecting Cut Radar Cable - Help Please

Radar Junction Box Splice Cautions:
1. Screened conductors: The screen or drain shield must be spliced adjacent to it’s core conductor, and the unscreened length of core kept to a minimum (<1.25").
2. Connect all power, data, & co-ax cables in the same sequence (on terminal strip) as used for manufacturer’s connector or terminal. Send & receive conductors will normally be adjacent to each other.
3. Small conductors: Take extraordinary care not to damage very small conductors.
4. Ferrites: Most manufacturers will recommend a specific ferrite bead, to be installed on each end of the splice.
Protection: Protect all cables from moisture, UV & weather exposure, mechanical abrasion, heat, etc. Avoid tight bends.

Excerpted from a previous discussion, with much more good advice (Rick & others):
Goto ➥ Furno Radar Install
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Old 26-05-2013, 07:52   #9
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Originally Posted by daddle View Post
I've seen this cutting nonsense done several times. The logic was to save 20 minutes while pulling a mast at the expanse of ruining a nice cable and creating a maintenance nightmare in the bilge. Ugh. The better thing to do is cut the hole a tiny bit bigger and fish the small end thru ... usually the antenna end.
I'm no expert, what when I pulled my mast for the refit earlier this year I went to Harbor Freight and bought a cheapo "non conducting" fish tape for under $10. It has two ends, and I used one to back pull the VHF coax and other for some other wire runs in the same area. It just sits there with the excess taped into a coil until I can get the mast finished and back in. Then I'll just pull the coax back to the radio without having to cut and splice it.

Although I believe the OP said he was running inside an arch tube, which is probably too small for the connector. Maybe an argument for running the cable on the exterior?

JRM
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Old 26-05-2013, 11:09   #10
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Originally Posted by montenido View Post
Hi all,

I know that this subject has been covered before, and I read as many threads about it as I could. However, I still have one question about the very small coax that is inside the radar (Furuno) cable. My cable has 18 separate wires inside, which are all being reattached using a long terminal block. That leaves one small (about 1/4-1/8") grey coax cable.

Now can I just separate the outside shielding and twist it into a wire, to be attached to the terminal strip? Then add a connector to the core wire and do the same thing? All the other wires are pretty easy.

BTW, I had to cut the cable to make the run inside my arch tube.

Thanks for any tips or insight.

Cheers, Bill
Is the radar up the mast?

Or permanently mounted to something else?

Instead of a terminal strip, I would use a round waterproof locking connector with sufficient pins to do the job properly.
For those the shielding goes to one pin, and everything stays nice and neat.
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Old 26-05-2013, 13:16   #11
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Re: Re-connecting Cut Radar Cable - Help Please

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Originally Posted by jgbrown View Post
Is the radar up the mast?

Or permanently mounted to something else?

Instead of a terminal strip, I would use a round waterproof locking connector with sufficient pins to do the job properly.
For those the shielding goes to one pin, and everything stays nice and neat.
Why don't you just supply us with an example of the connector that you so glibly recommend? 18 or more pins and waterproof... somewhat rare, likely to require a special crimper for the proprietary pins, bloody hard to assemble, expensive and so on.

The fact is that terminal strips do work, are recommended by at least Furuno for the job, are inexpensive, don't require any special tools or skills to install.

And for Daddle -- I would like to see you snake our cable from the mast to the display in 20 minutes. Took me over an hour and a few skinned knuckles. Then of course there is the issue of the cable ties bundling with other cables. Really, why not cut the wire? If corrosion is an issue (is not in our boat) spraying with one of the proprietary protective sprays will give good life to the setup. CRC makes several such in ascending degrees of permanence.

It was a no-brainer for me, YMMV.

Cheers,

Jim
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Old 26-05-2013, 13:30   #12
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Re: Re-connecting Cut Radar Cable - Help Please

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Originally Posted by jgbrown View Post
Is the radar up the mast?

Or permanently mounted to something else?

Instead of a terminal strip, I would use a round waterproof locking connector with sufficient pins to do the job properly.
For those the shielding goes to one pin, and everything stays nice and neat.
There you go, finally the proper way. Ther are plenty of "Cannon Plugs" for sale. Sure it takes a little skill, so? But it's not hokey.
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Old 26-05-2013, 14:49   #13
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Re: Re-connecting Cut Radar Cable - Help Please

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There you go, finally the proper way. Ther are plenty of "Cannon Plugs" for sale. Sure it takes a little skill, so? But it's not hokey.
The terminal strip is not "hokey". We all use terminal strips and crimped connectors for our power cabling, and with the proper technique and protection there is absolutely nothing wrong with it. In this radar installation, the shielded signal cable is carrying a fairly low-frequency video signal, and so with ordinary care a terminal strip connection will do just fine.

The Cannon connector won't provide a properly shielded connection anyway. At best, a metal-shell connector will shield the whole bundle of wires. However, the cable contains a single shielded conductor and a bunch of unshielded ones. Enclosing them all in the same shield will, if anything, make things worse. In practice, because the length of the common shield is only an inch or less, it's probably won't make any difference. But, neither will the terminal strip interconnect.

I suggest that the OP do what is convenient. If he expects to pull his mast regularly, a barrel connector may make for quicker connect/disconnect. Otherwise, the terminal strip is a good solution.
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Old 26-05-2013, 15:24   #14
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Re: Re-connecting Cut Radar Cable - Help Please

As confident as some of you sound about taking these kinds of short cuts, you will never find a critical piece of equipment that leaves the ground or goes into war using an exposed terminal board. I think this is another rationalization for doing it the easy way and just another reason sailboat equipment is so undependable.
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Old 26-05-2013, 16:03   #15
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Re: Re-connecting Cut Radar Cable - Help Please

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As confident as some of you sound about taking these kinds of short cuts, you will never find a critical piece of equipment that leaves the ground or goes into war using an exposed terminal board.
What exactly do you think is being proposed? I expect that a terminal strip in a vulnerable location will be appropriately protected. I don't think anyone is suggesting that a terminal strip be located so it could be splashed or damaged. My previous radar had a terminal strip at the mast base, inside a water-resistant box. The wires, including the shielded signal cable, were joined at the strip.
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