LORAN to GPS

[Connemara]

Folks: Probably a dumb question but I dunno much about these things.

I have a LORAN set in the cabin (swings out on a bar so you can see it from the cockpit), which I never use, because I also have a handheld GPS.

Question is this: If I mounted a GPS chartplotter in the same place, could I use the same antenna cable as the LORAN? The LORAN cable runs under the cockpit to a whip antenna mounted on the transom and Looks as if it would be a bugger to swap out.

Obviously I'd need a different antenna, but are the cables the same or even similar?

Connemara

[David M]

Probably not, but give it a try. It wont hurt anything to try. You will either get GPS reception or you wont. What type of coax is it? If you are having any doubts, run new coax. Water intrusion can destroy a coax internally..and you probably don't know the entire history of the boat.

LORAN and GPS operate at entirely different frequencies 100KHz vs 1.5 Ghz. Not that it will make a difference shielding wise. GPS requires well shielded coax. If it does not work then see what the manufacturer requires.

I kinda like old LORANS. They are very retro. The position accuracy is lousy but the repeatability in amazingly accurate. My inclination would be to keep the old LORAN working and run a new GPS cable...as difficult as it may be.

[AnchorageGuy]

Nope, cables and antenna are different but if you buy a plotter with external antenna it will come with a cable. Try your handheld in the spot you want to mount it. You might find you can use a plotter with a internal antenna and get a fine signal.

[fairbank56]

Which model Loran and GPS? Many Loran's and GPS's use the same rg-58 coaxial cable and would work fine.

Eric

[Connemara]

Well, the answer appears to be maybe. Good enough. When the time comes I'll try it. I can't recall the LORAN model; it's on the boat, along with the manual. And the chartplotter is completely notional -- I don;t have one yet and probably won' this year. But when I set out to purchase, I'll look for one that uses the same type of coax. Thanks all Connemara

[btrayfors]

Connemara,

I agree with Fairbanks56...the cable is likely to be some variety of RG-58. However, I would strongly suggest that you find a way to mount the GPS antenna with NEW cable -- RG8X or other low loss cable, because:

1. You don't know the condition of the existing loran cable; it could very well be deteriorated through age, water intrusion (water wicks along the strands internally), corrosion of inner braid), etc.; and

2. RG-58 cable has high losses at the frequencies used by GPS; RG-58X or the more exotic low-loss cables are better.

GPS is a pretty important system to have aboard and presumably you want it operating at full capacity. That means it's got to receive a strong, clear signal from the antenna.

There's gotta be a way to put in new cable...how hard can that be on a 27-footer? :-)

Bill

[svHyLyte]

If the LORAN works, I don't see the rationale for discarding it in favor of the GPS. LORAN signals are more robust than GPS and tho' the LORAN may require a bit more effort, it is a very reliable back-up to GPS. IF the GPS you have is a hand-held, it has a built in antenna and the odds are it will continue to work if mounted on the swing out bar (we had a Sitex 787C and Magellan 500DX mounted side-by-side on a similar swing-out bar on our old Cal 2-29 and the Magellan worked just fine without an external antenna). If not, you may find that your GPS will accept one of the remote antennas that plug into the unit itself that can be mounted on deck. For example, Garmin sells the GA 25MCX for $32.00 USD. (See https://buy.garmin.com/shop/shop.do?pID=1326 )

As for the LORAN, on our boat we have both and I use the LORAN as a back-up for the GPS. Interestingly, once the position off-sets were put into the LORAN we found that it's position report is always within a few hundred feet of the GPS Positions (with WAAS). For the sake of convenience, I usually have the LORAN set to a waypoint that's prominant on our chart. That gives me a range and bearing to the waypoint that I can use very readily, rather than having to plot Lat/Lons.

FWIW!

s/v HyLyte