Raymarine radar cable (pre ethernet)

[prv]

New boat has a Raymarine RD218 radar scanner, the kind that connects to a C70 display, so before it all went digital / ethernet but not absolutely ancient.

The cable was split and joined with a choc block to allow the mast to come down. The end at the bottom of the mast does not look good - almost too short, corroded, raggedy, and bound with PVC tape slightly further up, as if it's been pinched/crushed at some point.

This is obviously specialist cable - it has thick power cores, thin control cores, and a couple that look as if they might be coax that presumably carry the signal. It also looks like it might be difficult to disconnect at the scanner end, disappearing into a sealed metal box inside the radome.

Because of the second paragraph, I'd quite like to replace it with new. Because of the third paragraph, this is not as simple as replacing a lighting or VHF cable.

How necessary is replacement? By which I mean, will the raggediness of the cable be affecting the quality of the picture? Or is it actually a digital connection and if the two units can talk at all, they'll work fine?

How easy is replacement? In particular, can replacement cable be obtained, and what sort of connections are inside that metal box in the radome? While we're at it, presumably there's a better way of connecting the cables than choc-block?

Thanks for any insight from anyone who knows these radars!

Pete

 

[Talulah]

Replacement cables available on eBay or JGTech.
To connect at the Radome.
Remove Radome lid.
Feed cable through cable gland.
Small group of cables are in a connector block that plugs in.
Power cables with bared ends fit into a connector that you open the jaws of each connector by pressing down with a small scredriver.
There are 2 sockets for each colour. (4 in all.)
The lightweight cable just uses one pair. Heavyweight uses both pairs. The RD218 only needs the lighter weight cable.
The hardest job is feeding the cable up/down the mast. Use the old cable to pull a mouse line through.
Apply oil to the new cable to help slide it through.

 

[greenalien]

The end at the bottom of the mast does not look good - almost too short, corroded, raggedy, and bound with PVC tape slightly further up, as if it's been pinched/crushed at some point.

Before spending any money on a new cable, I'd get an electronics engineer to check out the radome and display head. These older cables are inclined to suffer from UV degredation which makes them split, admitting salt water. Once that's got inside, cable corrosion and short-circuits soon follow, causing other damage to the electronics, particularly the power transistors in the display head. You may find the cost of the new cable is more than the set is worth, particularly if it has other faults as well.

 

[prv]

Before spending any money on a new cable, I'd get an electronics engineer to check out the radome and display head. These older cables are inclined to suffer from UV degredation which makes them split, admitting salt water. Once that's got inside, cable corrosion and short-circuits soon follow, causing other damage to the electronics, particularly the power transistors in the display head. You may find the cost of the new cable is more than the set is worth, particularly if it has other faults as well.

Well, in a way I'd love an excuse to go out and buy a new set . But the inside of the radome looks brand new and squeaky clean, nothing been leaking in there. And since the cable is split and joined with choc blocks in the cabin headlining, there's no continuous route for any water in the cable to run down to the plotter, which seems to be working fine.

Pete

 

[prv]

Replacement cables available on eBay or JGTech.
To connect at the Radome.
Remove Radome lid.
Feed cable through cable gland.
Small group of cables are in a connector block that plugs in.
Power cables with bared ends fit into a connector that you open the jaws of each connector by pressing down with a small scredriver.
There are 2 sockets for each colour. (4 in all.)
The lightweight cable just uses one pair. Heavyweight uses both pairs. The RD218 only needs the lighter weight cable.
The hardest job is feeding the cable up/down the mast. Use the old cable to pull a mouse line through.
Apply oil to the new cable to help slide it through.

Thanks for this. You're saying there are only the small data cables plus power? I had thought I saw some other bigger ones, but I admit I didn't look very carefully, perhaps they were just the power cores (especially if there are two sets).

Don't suppose you know what kind of signals the data cables carry? Digital would be ideal as I can then stop worrying about dodgy connections degrading the picture. If there aren't any coaxes in the bundle then I guess the choc block is adequate, though I might still replace it with a decent connector.

Cheers,

Pete

 

[Talulah]

Analogue signal. There is a shielded co-ax amongst the wires.

 

[prv]

Analogue signal. There is a shielded co-ax amongst the wires.

Ah. I took from this:

Small group of cables are in a connector block that plugs in.
Power cables with bared ends fit into a connector that you open the jaws of each connector by pressing down with a small scredriver.

that there were only the small group of cables and the power cores.

How does the coax connect to the radar? Is there a small BNC or something? Or soldered?

Since the ape that fitted it put everything through the choc-block, the signal in that coax must be being degraded substantially. I guess this will affect the picture. People who casually joint RF co-ax as if it were a simple power supply are a real menace. Building-site sparkies are notorious for doing it with TV cable.

Cheers,

Pete

 

[Talulah]

The coax is already connected in into the block connector. You don't have to worry about it seperately at the Raydome.

 

[prv]

The coax is already connected in into the block connector. You don't have to worry about it seperately at the Raydome.

OK, thanks.

Since there's apparently analogue signalling involved (coax could be digital, but seems unlikely) I want as good a connection as I can get between radome and plotter. So I think I'm going to have to look at replacing the cable. Wish I'd decided that earlier - I only have this weekend before the mast goes back up, so I might have to be climbing...

Pete

 

[Talulah]

While it's on the ground I suggest you measure which length of cable you want 10m or 15m.

 

[prv]

While it's on the ground I suggest you measure which length of cable you want 10m or 15m.

Already measured where everything is on the mast, for future reference

The bottom of the radome is 5.5m above the mast foot, the question is whether 4.5m is enough for connections at each end plus a possibly tortuous route from mast step to plotter (which might well be moved from its current position at the chart table to up on deck under the windscreen). I guess it probably is, but do I want to take the chance?

Pete

 

[greenalien]

there's no continuous route for any water in the cable to run down to the plotter, which seems to be working fine.

The potential problem isn't water getting into the plotter - it's that there may have been a short in the cable, which causes damage to the plotter when you try to transmit - the rest of the plotter functions may still be OK - only way to find out is to connect everything up, much better to check this while your mast is still down.

Well, in a way I'd love an excuse to go out and buy a new set

I'm doing my best...

 

[prv]

The potential problem isn't water getting into the plotter - it's that there may have been a short in the cable, which causes damage to the plotter when you try to transmit - the rest of the plotter functions may still be OK - only way to find out is to connect everything up, much better to check this while your mast is still down.

Understood.

I did try the radar while the mast was still up, when we were looking over the boat before buying her. It fired up and drew blobs all over the screen, so I don't think anything has been fried.

The blobs bore no relation to the shape of the land though. While I'm no expert I do have a rough idea about things like beams travelling over beaches and bouncing off higher ground inland, and even allowing for that (and knowing the area) there was no real correlation. That's why I suspect the signal may be being degraded en route down from the mast.

I think I've convinced myself (with help from this thread, especially Talulah) to replace the cable. I've just heard that the yard want to put the mast back up earlier than I'd expected, so it's definitely a climbing job unless I can get my hands on a cable locally (but I'd rather climb than pay what some places are asking!).

Pete

 

[greenalien]

It sounds as though it will be worth risking the expense of a new cable - better if you can route it through your deck with no joins, even if it means a big cable gland. Although this means more hassle when removing your mast, it'll give you a more reliable installation. It's also a good idea to protect the cable between mast and cable gland with a few turns of self-amalgamating tape to keep the U/V off. Good luck!

 

[prv]

It sounds as though it will be worth risking the expense of a new cable - better if you can route it through your deck with no joins, even if it means a big cable gland.

Ah, well, I now have (on my dining table) a very big cable gland. One of Salty John's finest Cableports, which should happily pass a radar plug. I was indeed thinking of keeping the cable unbroken, though unthreading the cable to the plotter will be pretty fiddly above the headlining, especially if I do move it above deck rather than at the chart table. Of course, now I no longer need to varnish my mast, and nobody round here brings them down for the winter, it will probably be staying up until the rigging is 10 years old in 2019. So worth the hassle.

Pete

 

[pvb]

If you do end up putting a new cable in, make sure you include a generous loop of spare cable inside the headlining, so that there's be plenty of spare in case it's necessary to add a join at some point in the future. Frankly, I'd be tempted to wait and see how the thing works before going to all that trouble anyway.

 

[prv]

Frankly, I'd be tempted to wait and see how the thing works before going to all that trouble anyway.

Well, as mentioned upthread, so far it appears to not work very well

Admittedly, my main reason for sorting it out now was that it would be easier while the mast was lying down. But I just heard today that the painters have finished earlier than I expected and are hankering to put the mast up, so unless someone local pops up this week offering a roll of cable at a reasonable price, I probably won't be fitting it on the ground anyway.

Pete

 

[pvb]

Well, as mentioned upthread, so far it appears to not work very well

In fairness, you don't know what the settings were, the heading could have been completely off, etc, so it might be worth getting to know the radar before assuming it doesn't work properly due to the cable.

 

[prv]

In fairness, you don't know what the settings were, the heading could have been completely off, etc, so it might be worth getting to know the radar before assuming it doesn't work properly due to the cable.

Not disagreeing, I just don't like raggedy cables, and I especially don't like RF cables joined with choc-blocks.

Pete

 

[pvb]

I reckon lots of radars are cobbled together with choc-blocks! And mostly, they work. No joins in my radar cable though, as I have a nice sensible stern pole mount.