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Old 18-07-2007, 00:22   #1
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Extending Radar Cable

The cable between the radardome and my chartplotter is to short , would it be possible to extend it without loosing quality of the signal ?

Thanks and regards
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Old 18-07-2007, 01:01   #2
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Radar Cable cutting splicing

Hi Bobs
I had a situation which needed a small cable diameter to lead through a special pole so I cut the radar cable and rejoined after running.
I noticed no difference in radar output
I know you can purchase different length cables
Steve Marshall
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Old 18-07-2007, 01:23   #3
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Hi Stevem,

I know they come in different lenght , it's a raymarine , and as you well know the prices are outrageous.

Greetz
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Old 18-07-2007, 06:42   #4
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You don't say how much extra you need or which scanner you have but, I have a bunch of 10meter (light)(2 power cores) cables. They are not extension cables but you can make your own out of one of them. The Raymarine number is M92692. You can have one for the price of shipping.

Eric
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Old 18-07-2007, 11:33   #5
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I have spliced/extended/shortened numerous radar cables. They actually can be cut and connected through a terminal block without any noticable change in performance. The main issue is a setting - Sweep Timing, that must account for the "travel time" of the video signal through the cable. Many units, esp. older ones, will require a service manual to find the adjustment inside, and it has to be checked/adjusted on a sea trial. Some older Furuno units have the adjustment accessible from the front panel, under a little cover. New Furunos have the adjustment in the installation setup menu.

To check sweep timing, you must take the boat out and position in front of a long straight target, like a commercial warf, bulkhead, bridge, etc. Correct sweep timing will display a straight line, incorrect setting will display a line either dipped or peaked at the center. Incorrect sweep timing will cause targets to be displayed at incorrect distances.

The above does not apply if your scanner (dome) is digital (it will have a very small cable). You should be able to extend the cable a reasonable distance with no troubles.

I also have some extra cable, for Furuno.

NEA
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Old 18-07-2007, 21:52   #6
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Thanks for the respons.
The chartplotter concerned is a raymarine C80 plus , combined with radome 4kw.
So if I understand correctly , those cables are plain copper wire with suitable connections at the end.
Man , this is a sheer rip off by raymarine since they cost a fortune.
I probably can lay my hands on a 30 feet cable , but for mast-mounting in a 40 feet sailer that wont do the job.
The sweep time thing does worrie me though , since I have no service manual and so on.
Maybe one of you guys have a spare 50 feet cable which i would very happy to buy from you.
Shipment is to Europe mind you.

Thanks a lot allready
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Old 19-07-2007, 09:57   #7
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Sweep timing will have to be set for the cable length, regardless whether you've extended (or shortened) the existing cable or bought a complete longer cable. Radar cables for all brands are very expensive. Cables vary in configuration between brands and models, and usually have two shielded groups, plus one or two coaxial cables. If there are enough conductors in each group you can mix & match cables, but must make sure the end-to-end connections don't get mixed up.

The cable I have is Furuno, brand new, connector cut off one end, about 45' long, has 11 small wires in the inner group + 1 coaxial, and 10 larger wires in the outer group.

You can't get around that timing issue, you must get the info to do it. You can make those connections with a variety of cable/wire configurations.
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Old 19-07-2007, 10:20   #8
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This thread implies that splicing the waveguide (cable to the radome) is also acceptable. Don't you have to worry about reflected energy at the splice / connector similar to VHF / SSB radio waveguides?


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Old 19-07-2007, 13:26   #9
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There is no RF in the cable, the signal coming back is video. Waveguide is inside the scanner unit between the magnetron and antenna. Very old units used RF amplifiers located away from the scanner.
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Old 19-07-2007, 14:59   #10
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That makes perfect sense - thanks!

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Old 19-07-2007, 23:40   #11
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EngNate,

you seem to know a lot about this stuff , could you tell me why do these cables, and perhaps in particular raymarine , are so expensive ?
I'm affraid a furuno cable wont help me very much because the connections are different and dont have the raymarine-layout.
Thanks anyway.

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Old 20-07-2007, 08:41   #12
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My connections at a terminal bloc are getting a bit corroded will a readjustment be required if l trim back 5 or 6 inches to get some clean wire to reterminal? Furuno 1720
Dave
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Old 20-07-2007, 08:49   #13
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Excerpted from the earlier discussion “Furno Radar Install” at:
Furno Radar Install

Radar Scanner Cable Splices:
The problems associated with scanner cable splices are legion, even tho’ subtle. Perhaps Rick (and now EngNate) might elaborate.
Unshielded terminal strips are likely to create problems with signal loss, timing delay, signal interference, and/or EMI radiation.
There are (a dozen or so) small wires, difficult to work with, and it’s difficult to keep untwisted and/or unshielded lengths to minimum, while spreading out to mate on terminals.
I’d (when practicable) prefer to use a proper, weather-proofed, barrel-type locking, shielded plug set, comparable to the OEM set supplied with the cable - or a manufacturer’s cable extension set.

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.

I’m certain Furuno provides cable length, connection & splicing cautions & instructions in their manual.
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Old 20-07-2007, 08:59   #14
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Whew Gord...quite a mouthfull....considering the existing condition of the connections and the excellent radar imaging l am receiving...l would hope a "cleaning up" would only serve to improve things.
Dave
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Old 21-07-2007, 09:28   #15
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A few inches trimmed won't have any noticable effect on the timing. The precision of the adjustment is not that fine.

Gord pretty well covered the details of practice in actually making the splice or connection. Where EMI is concerned, it's noise from external sources that you want to keep out of the radar signals. You definitely want to keep moisture out as it will migrate up the cable and affect signal quality. If you look inside many scanner units, especially older models, cable dress isn't much of an issue. (The old Pathfinders had a long strip of push-on connectors inside, and plenty of loop-length to make assembly easy.) New units I've been into are much neater, but newer circuitry is actually more immune to interference. Ferrites are placed on the cable in the scanner to prevent stray RF from following the cable and possibly interfering with other equipment. Most of the wires carry analog power and control voltages, modern recreational radars are designed to keep sensitive circuits together at one end or the other. As Gord said, you want to keep the circuit wires grouped and shielded as they are in the cable, and minimize extra length in the wires, especially shields. You want to keep separate shields separate, even though they are connected together at one or both ends. Usually there are two groups, separately shielded to prevent signals bleeding from higher power circuits in one group to low-level signal circuits in the other.

Splicing a radar cable does require a fairly high level of proficiency in soldering and wiring, and I realize I have spoken of it as though it was a little simpler than it is in practice. It's not something to go at lightly when you are responsible for a customer's several thousand $ equipment, nor your own. A connector set, e.g., AMP CPC Series, is good for mast installations that may have to be disconnected in the future, but these require as much or more skill to install properly, as you have to work with very short and precise wire lengths and very close spacing. You can end up with a ball of spaghetti that won't fit into the connector shell, and excess bare wire at the terminations can short to other conductors when assembled, possibly damaging your equipment.

I ought to have included words of caution from the start - it's not as easy in practice as it is on the screen. You must be fully proficient in the required skills. An inline splice requires technique for overlapping and soldering shields without damaging the insulation of the conductors below. Conductor splices must be staggered, and each length conforming to the overall splice length. The conductors must be twisted together neat, tight and close, and the length still conforming to the overall splice before soldering each. Proper cutters and cutting technique is required to insure that a strand of wire cannot poke into another conductor. One of these splices takes me a couple of hours or more to do - it may be cheaper to buy the cable - when I have to do it, saving $ on the cable is not the reason.

All interconnection cables for marine electronics are high priced. The manufacturers nail us on these to help make up for competitive pricing of the units. It is a rip-off, but since they all do it, we're stuck. Radar cables are that much more expensive because they are custom made for the electronics manufacturers in volumes that are nothing in the wire & cable industry.

I did once take a series of photos of making a radar cable splice, & do promise to annotate and post them sometime soon.
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