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DGPS Antenna Problems

Old 03-30-2003, 10:36 AM
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jlr
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Default DGPS Antenna Problems

I am having trouble receiving a consistent signal on my new DGPS antenna (Raystart 120) going to my 420 Raymarine chartplotter. I know that the antenna is supposed to have an unobstructed view of the sky.My old non DGPS antenna was mounted on my center console and worked fine. I added a T Top over the center console and DGPS antenna mount and switched to DGPS on the same mount on the center console.Could the T Top be causing the problem or is it more likley the new DGPS antenna? I did not think that the T Top could make that much difference since it only has a canvass top but it does have aluminum supports on top. Any help would be appreciated.
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Old 03-30-2003, 12:22 PM
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Default DGPS Antenna Problems

The Raystar 120 is what Raymarine calls a Satellite Differential GPS. Other manufactures simplely call it WAAS, the Goverment name for the system. The Geostationary Satellites are more difficult to receive. They are low on the horizon. There are only two of them. One off each coast. You will receive signals from up to 12 satellites, but only one Geostationary for correction, unless you are on a mountaintop in Colorado. You will improve reception if you mount your sensor in a place with no obstructions. Mount it on top of your T top and things should improve.

[This message was edited by kglinz on 03-30-03 at 03:09 PM.]
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Old 03-30-2003, 03:24 PM
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Default DGPS Antenna Problems

jlr, proper WAAS reception (and antenna location) is generally going to be much more critical than straight GPS.

The other thing will be your location as WAAS reception can be limiting depending on your location.

Cheers, Kerry.

I never get lost, everybody tells me where to go!
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Old 03-30-2003, 09:45 PM
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Default DGPS Antenna Problems

Strictly speculation on my part, but I thought that I had a fixed reference point right at the mouth of Tampa Bays shipping channels (which I'm just south of.. and that there were numerous known fixed sites that were referenced depending on your units geographical location. Is there any web sites where you might be able to read on that?
Another note: I don't know if it's applicable in this case or not, I've got an older DGPS and it's got three antenas..each one came with approx. 50' of cable and although it wasn't needed, it was noted not to shorten it or poor reception could be a result.

2 cents isn't much, but in a pinch....
Good luck,
Chris
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Old 03-31-2003, 05:24 AM
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Default DGPS Antenna Problems

Still not sure of the answer. Will the T Top interfere with the antenna. I have other DGPS antennae (on Northstar's) mounted under my bridge (ie enclosed by fiberglass) and I have no reception problems. Since I can not snake the cable through the new T Top, I am reluctant to move it up top if it will not make a difference.
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Old 03-31-2003, 08:20 AM
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Default DGPS Antenna Problems

jlr

I had to relocate my 120 from helm to hard top last week, had problems with "lost fix" dropping from SD-Fix to Fix to lost fix. Nav page would show good signal strength with 4 Sat "in use" and several "spare" then drop fix. Sat 22 must be the SD Sat. When I set the 120 on top no more fix problems.

Just lay the reciever on the top, connected but not hard mounted and see if you problems disappear.
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Old 03-31-2003, 08:22 AM
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Default DGPS Antenna Problems

Don't mount the sensor permanently. Just put it on with tie wraps and check the operation.
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Old 03-31-2003, 08:29 AM
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Default DGPS Antenna Problems

Thanks. I too am having fix, lsot fix problems. I guess I have no alternative but to remove it from the console and find another spot not uner the T Top. With everything going on in the world today, I wasn't sure if it may have something else wrong with the signal.
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Old 03-31-2003, 02:44 PM
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Default DGPS Antenna Problems

jlr, what's your location in the US as depending on that there's a slim chance that you might not even receive an adequate signal in the first place.

Cheers, Kerry.

I never get lost, everybody tells me where to go!
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Old 03-31-2003, 02:59 PM
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Long Island, New York--more precisely, Huntington New York
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Old 03-31-2003, 10:00 PM
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Default DGPS Antenna Problems

Signal from AOR-W (PRN#122) shouldn't be a problem as it's elevation would be approx 35 degrees, POR (PRN#134) is below the horizon.

Cheers, Kerry.

I never get lost, everybody tells me where to go!
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