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Old 14-08-2020, 11:31   #1
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Help Identify Old GPS Mount

I need help identifying an old GPS mount to find out what model GPS unit fits it. Otherwise, I'll remove all the wiring.

The GPS antenna is Garmin and the connector seems to be a Garmin proprietary 6-pin flat according to this:

I contacted Garmin and after a week of back and forth, they claim it is not theirs because "Our antennas are always going to have a puck shape and connect with NMEA 0183 or NMEA 2000 which is not a 6 pin connection." - even though GARMIN is molded into the antenna base plastic.

Does anyone here have any idea of what Garmin GPS Unit (or other brand for that matter) belongs in this mount?

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Old 14-08-2020, 16:43   #2
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Re: Help Identify Old GPS Mount


1) Well, no matter what we come up with (I also suspect it's an older Garmin or an old Magellan unit, that used to be mounted there), there are going to be few uses for that old mount...but...

2) But, don't pull the old wiring out, yet!!!

Have a look at the white cable....the one from the I suspect it is coaxial cable (like you have running to a marine VHF antenna)?

I cannot tell from your pic, but just a quick look at the cable (at the end inside the cabin, that appears to be cut-off), and you should be able to tell....
Is it a coaxial cable (under the outer-jacket it will have a braided shield, and then some insulation and just a single wire in the middle)...or is it a multi-conductor cable (with 4 to 6 wires inside)?

If it is coax, then you can be sure that what you have there on the rail is an antenna, just an antenna....and not a GPS receiver...

You see, in the past 20 years, most consumer marine electronics "GPS antenna's" are actually entire GPS receivers built-into the antenna enclosure, and outputting position data, SOG, etc. etc. via NMEA0183 or NMEA2000, or SeaTalk, etc....they are not just antennas, they are entire GPS receivers (sometimes called GPS "pucks"), they have a multi-conductor cable....if it was just an antenna, it will just have a coax cable...

3) But...exactly what was mounted there? (again, I suspect an older Garmin or Magellan GPS)

a) FYI, older GPS units / older standalone GPS receivers would have external antennas, that were just antennas...(connected to the receiver inside via coaxial cable)

b) And, many standalone portable/handheld GPS receivers have accommodations for permanent mounting and external antenna connections (as well as external DC power and NMEA data in/out)....and this would also just have a coaxial cable connecting the rail-mounted antenna...
{and, yes, despite what Garmin told you on the phone, this does include Garmin units!!!}

c) Although rare (and almost exclusively from Furuno), if your rail-mounted antenna is fed with coax, it could be a LW antenna...for receiving NAVTEX weather....or for receving old D-GPS "differential-correction" signals...{fyi, this is very unlikely}

4) Now, you're saying, "why do I care?"....well, maybe you don't....but you did ask the question here....

And, if this cable is coax (and it is in good shape), it can be used for other antennas...

--- such as a MF/HF-DSC Receive antenna for use with an M-802 (a MF/HF-DSC-SSB Radio), etc.?

--- or perhaps you need an additional marine VHF antenna (for either an AIS transponder, or second VHF)?

--- or maybe you desire to install an AIS transponder (and you have a steel or alum hull and deck) and cannot get good GPS reception below decks, so you desire to mount the AIS's GPS antenna out on the rail?

{please note that AIS transponders are the exception to the modern consumer marine electronics having the entire GPS receiver inside the AIS transponders have their GPS receivers built-into the AIS transponder itself, and require a GPS antenna be connected (although those with fiberglass decks, can usually have good GPS reception below decks, so no rail-mounted GPS antenna is needed)....but an externally-mounted VHF antenna is of course, needed!}

5) Now, worst don't need/want to have vhf or gps antenna there on the rail, and therefore you want to rip-out all the old wiring....please either pull it out with a pull-string in its place (allowing you to more easily add some wiring later), or use the old wiring as the pull-string and pull in some new wiring/cable for what you actually might want there, or near there....(NMEA wiring....etc. etc...)

I do hope this helps?

Fair winds.

John, KA4WJA
s/v Annie Laurie, WDB6927
MMSI# 366933110
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Old 14-08-2020, 19:25   #3
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Re: Help Identify Old GPS Mount

Thanks for the thorough reply, John!

I'm heading to the boat tomorrow morning and will take some more pics, but I believe the white cable that runs to the antenna has a BNC connector on the end, and is not cut.

The pin-out diagram link I posted has a link showing that three of the pins represent "alarm," "data in," and "data out." No mention of NMEA 1083 or NMEA 2000 so it must be ancient stuff (although the wiring looks to be in very good shape for being in a 36 year old boat).

I've Google-searched every Garmin GPS unit I can think of looking for connectors, etc., and can't find what it is. I searched for old LORAN systems as well and didn't see any Garmin offerings that matched. I imagine whatever it was probably didn't become very popular.

I'll leave it there for the time being. I just figured if it was for a system I could drop in and get some use out of, it was worth saving as it's already wired and ready to go.

Real head scratcher for sure. I'll Google old Magellan units and look for similarities. Can't believe Garmin doesn't even claim the antenna though because it's definitely a Garmin product.
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Old 16-08-2020, 06:46   #4
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Re: Help Identify Old GPS Mount

Here are some pics of the wire end and wire labeling, if that helps anyone...

Wire says: COMMSCOPE NETWORK CABLE 5569 RG 59/U E82833 20 AWG 75C (UL) TYPE CL2
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Old 16-08-2020, 08:35   #5
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Re: Help Identify Old GPS Mount

It's obsolete and useless, either radio or GPS, it could be replaced by a single DSC handheld radio for less than $200. Don't waste time trying to find a 20 year old piece of gear to fit some left over accessories. Whatever you get to replace it will come with a mount and antennae.
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