GPS Plotter antenna location?

[reelfishin]

I am installing a Standard Horizon GPS Plotter on one of my boats, they really don't give you much instruction as to where to place the antenna. On my other boats I always mounted the antenna on the roof, but this is an open boat with only a small area on the bow. I have an aluminum windshield frame but that has a canvas cover that attaches to the top edge, so I can't bracket it off the edge, and I don't want to accidently shield one side of the antenna with the windshield frame.
Does anyone know how far away the antenna should be from other objects? Can I just mount it on the surface of the bow on a short stand? Or do I need to come up with a tall stand that puts it above all else?

 

[Boatist]

Re: GPS Plotter antenna location?

Antenna needs to be in a place where it can see from horzion to horzion if your in the far North or Far South. However I am at 38 degrees North and the WAAS birds are near 45 degrees above the horzion, so really not that critical in my location. If you are closer to the equator than 30 degrees North or south then WAAS birts will high above the horizon and easy to receive so mounting of the antenna not critical at all.

You might even try under your canvas top on a home made bracket to put it even with or slightly above the window frame on the side opsite from your helm. At this location not likely to be blocked by someone standing up and all I have seen work good under the canvas. Try just holding it in that location first and see it you get one of the WAAS birds. If you do then make a simple bracket to mount it.

 

[reelfishin]

Re: GPS Plotter antenna location?

What I am thinking of doing is a rail mount on a piece of PVC tube up high, that way it's out of the way of fishing out back, and it can be higher than the windshield. I'd rather stay away from the windshield frame all together, I have plans for a light bar overhead for night running. I don't always have the top on, so anything under the cavas would have to be mounted off either the windshield frame inside or off the gunwales and that just wouldn't work either way. On my last boat I had a hard roof, I put a 4" tube mount and just screwed the thing down. That worked great.
I used to install GPS locating devices in trucks, we could put the antenna anywhere that it was not in direct contact vertically with metal. It could be mounted on a dashboard or on the roof, either worked. I see several companies selling replacement antennas for plotters that look like those antennas, most are amplified antennas, or at least advertised that way.
I never had a problem with the on the road type of system with an indash mount, we used to hide them so to avoid tampering, so they got mounted in dash vents and under dash pads all the time. Those systems used a dual antenna system, the GPS unit would track the vehicles location, then the unit would transmit the location real time back to a tracking center which displayed the info online. I had even had vehicles show up on the system that were indoors, they usually showed up on screen minutes after they were powered up and got their first satelite fix. But if the vehicle was parked under an overpass, it would continue to show it's last position until it reimerged from the overpass or tunnel.

I was surprised at how little info they give you on setting these things up, they pretty much only tell you the specs, and you have to figure it out from there. Common sense tells you that it needs to have a clear view of the full sky, but they make no mention of that in the manual.

 

[Boatist]

Re: GPS Plotter antenna location?

Mounting it on the dash will work good for the normal GPS satellites as they are overhead and all around. Only time you really need an external antenna is to get the WAAS error corrections signals. These WAAS birds are Geostationary so must be over the equator. The farther you are from the equator the lower on the horizon they will be. Accuracy with out getting the WAAS signal about 30 feet. With the WAAS signal can be down to about 10 feet. On the bow on a pole is fine, even just at the bow rail height will work most of the time unless your in the far North or far South.