Garmin Data Cable Crossovers

[Roger Long]

I'm going to put an access plate in the base of my mast to get at the connectors so I just cut the Garmin network cable for radar and will have to install a coupler. This will require putting new modular plugs on and there are two different cable ends. Get it wrong, and the display won't know that the radar is there.

I had to sit down and draw this out. It looks like a lot of work but CAD actually makes it quicker and easier than scribbling on the back of an envelope.

There is an "A" and "B" end to the data cables and they are not marked. You have to look at how two of the wires are reversed according to this table:

Here is the standard, single cable setup with "A" plugged into the radar. It will also work with the cable reversed.

The cable that came with the radar wasn't long enough in my boat so I had to buy a 6 foot extension cable and a coupler. I went to the boat today and determined that I had put the "A" end into the chartplotter display unit. I also deduced that the coupler must have the wires crossed over inside it.

Note: I've shown plugs into the connectors with the 1 pin position reversed from it's actual orientation in the units so that the connector schematic will show a crossover instead of appearing to be straight through.

I could have put the extension cable in the other way or still reverse it as shown here:

Here is the coupler I have to add. I have shown an "A" end coming out of the deck because I would like to be able to plug the radome in here for testing when the mast is down and elsewhere.

Note that this means I will now have an "A" end coming out of the mast. Should someone ever attempt to test the radome mounted on the mast by plugging a display unit into it while it is off the boat, the radar won't work and this could lead to misdiagnosis such as thinking the cable is compromised.

By taking the minimal trouble to reverse the extension cable as shown here, I can have consistent cable runs and ends all the way through.

I think it's worth doing and something to think about if you are doing a new installation that involves extension cables and couplers.

 

[Tim R.]

Wow Roger. Seems like you have made something that should be relatively simple very complex.

I did the same thing in my sail locker because it was a impossible to route my cable without cutting it. I simply installed a terminal block and connected each like colored wire.

BTW, the Garmin wiring for their network components are Cat5e Ethernet spec. You can buy all kinds of connectors and cable at HR Distributors to help you out.

 

[Roger Long]

You can buy all kinds of connectors and cable at HR Distributors to help you out.

Yes, that's where I bought the crimper I need. It's all very simple when you just plug and play but, since I had to cut the cable and need to crimp on two new terminals, getting it right is worth the effort. I'd hate to get the mast up and have the radar not work.

Sometimes, the only way to route a wire is without the plug and knowing how to get the wires arranged properly before crimping then becomes important.

 

[Tim R.]

Roger, make sure your connectors and cable are compatible. Stranded wire is much easier to crimp on RJ45 connectors. Solid cable is no good. Even if you get it right initially it will eventually fail.

There are 2 types of conductors for Category (X) cable...Solid and Stranded. Solid conductor cable is what is typically used in most cables for your Category 3/5e/6/etc cables. Stranded conductor cable is what is used for patch cords as it needs to be flexible to patch from panel to switch etc...So they sell both kinds of RJ Mods to crimp on the cable. A big noob mistake is to buy solid conductor cable and put stranded mod's on it. Stranded mod connectors are more available/lying around/etc...so the are at hand. And usually someone has a box of Category cable laying around from the last workstations installed...so they crimp them on...and they will fail...if not now but soon...as they are the wrong type of RJ MOD's...Sounds silly to say it...but you need the right mod for the right cable. Stranded cable costs a lot more then solid core...so that's a big reason why folks grab it to make their own cords.

Find a way to use a punchdown block(female) and then buy a factory made patch cable. I have a punchdown tool you can use if needed.

 

[Roger Long]

Roger, make sure your connectors and cable are compatible.

That's why I paid many times as much for the Garmin connectors instead of buying them at HR. They are going on Garmin wire are the same as the connector kit that came with cable and radar. I took the connector into H&R and had them verify that the crimper I bought was compatible.

The Garmin instructions say to use an "AMP Modular Plug Hand Tool and Die Set (or compatible equivalent)". HR said those cost a couple hundred bucks and the only difference between them and the 20 buck DL-1008(RJ45/8P8C) Telephone Plug Crimping Tool they sold me was the longevity of the tool and not the quality of the crimp.

Do you think I'm on the right track? Considering the hassle if the radar doesn't work once the mast is up, it's worth getting this right.

Considering how much stress the Garmin instructions put on minimizing unshielded wire in the terminal connections (they even give you metal foil to wrap around the cut end), I'm intrigued that you were able to get by with a terminal block.

 

[Tim R.]

The key would be to use a cable tester from end to end(at your chartplotter and radome). If it says the cable is good, you should be alright.

I do not recall my cable being shielded. But if it was, that little bit that is now missing has had no discernible effect on the performance of the radar. I will be at the boat tomorrow and will check to see if it is in fact shielded.

BTW, when I did this, Garmin said not to cut the cable. There was no connector kit offered at the time. When I pressed the subject, the tech admitted that it is ok to cut and splice.

 

[DougM]

I see what you have done and I think I understand it. However, since the original connectors were already wired correctly, why wouldn't you just have made a straight through connection at the deck? Perhaps then you could have used a mil spec connector which would appear to be more robust and hopefully less susceptable to water intrusion.

 

[Tim R.]

Also, you can buy couplers either straight thru or crossover. All of your cable crimps should be the same. When you look at them the colors should be in the same order.

 

[Roger Long]

Also, you can buy couplers either straight thru or crossover. All of your cable crimps should be the same. When you look at them the colors should be in the same order.

Garmin cables all have two of the conductors reversed in the plugs. I'm also using the Garmin couplers since they have threads for the watertight covers on their standard plugs. I'm trying to keep it all in the standard Garmin arrangement to make it easier to figure out if making any changes, upgrades, additions, or repairs down the road.

 

[Tim R.]

Good info Roger. I would like to add something similar to make my backstay mounted radome easier to remove. Right now the pole sits in the cockpit all winter. The ramdome does come off though.

 

[sailingdog]

The Garmin cable appears to be standard ethernet crossover cable. The pinouts for a standard ethernet cable are:

1-1
2-2
3-3
4-4
5-5
6-6
7-7
8-8

With pins 1, 2, and 3, 6 being used for data transmission/reception.

On a standard ethernet crossover cable, the pins are

1-3
2-6
3-1
4-4
5-5
6-2
7-7
8-8

Again, with pins 1,2 and 3,6 being used for data transmission/reception

Electrically speaking, it doesn't matter which end of the crossover cable you plug in, since the result is the same either way. There really is no A-end or B-end, except with reference to the wire insulation colors.

The crimp quality of the cheap crimpers isn't quite as consistent as that of an AMP-type ratcheting crimper... I have them, since I work with networks for my day job.

BTW, IIRC, the Cat 5e specification requires that the length of the unshielded, untwisted wire at the connector be no more than .5". Of course, the reason for this is to prevent electrical interference, and the reason Tim may have gotten away with using a terminal block is that there really isn't a lot of electrical interference on a boat, at least compared with your average LAN patch panel or wiring closet.

 

[Roger Long]

The Garmin cable appears to be standard ethernet crossover cable.

They are. In fact I used standard cables and connectors from the computer store for a couple weeks while waiting for the Garmin parts to come in from back order.

The crimp quality of the cheap crimpers isn't quite as consistent as that of an AMP-type ratcheting crimper... I have them, since I work with networks for my day job.

Due to the cost of the Garmin plugs, the first two crimps I make will be the ones I'm depending on in the fogs of the Bay of Fundy. Do you think my 20 buck crimper is up to the job?

Do you think it would be worthwhile for me to get the plugs all set up and the wires inserted and then hire someone with an AMP crimper to come to the boat and make the crimps?

 

[Tim R.]

Roger, I used to have a ratcheting crimp tool for rj45. I have not made any cables in years. I will take a look around to see if I can locate it.

 

[Roger Long]

By taking the minimal trouble to reverse the extension cable (the one connected to the display) as shown here, I can have consistent cable runs and ends all the way through.

I think it's worth doing and something to think about if you are doing a new installation that involves extension cables and couplers.

I went up to the boat and reversed the cable today. Well worth the trouble. Having an oddball cable in the system means that, if you damage it, you can't just buy and plug in another cable which could even be a standard network cable from a computer store in a pinch. You'll have to buy plugs, a crimper, and possible cut a good factory end.

As long as you are using factory cables and standard cross over couplers, you can just plug stuff together in any arrangement and it will work. As soon as you cut a cable and install new plugs, it's well worth getting them right which means having all the cables in the same A-B or B-A orientation.

 

[Tim R.]

Roger, what are you suing for the power connection? Is it weatherproof?

 

[Roger Long]

Roger, what are you suing for the power connection? Is it weatherproof?

I haven't decided yet but it may just be a two prong trailer lighting connector. Once taped up inside the mast it should be fine.

BTW I ran into a very interesting issue with the 4 prong Cole Hersee connector for my mast lighting last spring that led to the mast being stepped twice. If anyone is using these, I'll explain it sometime. If you have one, replace it every few years.