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Old 14-10-2013, 11:25   #1
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GPS WAAS Antenna Location : Masthead or Sternrail?

Hi - what's the consensus on best position for GPS antenna?
If on masthead, has clear horizon but moves around alot more ,
and would be less accurate? On stern-rail, easy access, shorter cable, less movement, but reception hole in direction of mast / heeled over hull?
This is on a 10M steel sailing yacht.
Any advice would be appreciated - TIA
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Old 14-10-2013, 11:31   #2
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

Sternrail

There is too much movement at the masthead for it to be an ideal location.
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Old 14-10-2013, 11:43   #3
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

Lower is better. On my B393 mine is inset in the coaming. Just under the blue dink davit line.

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Old 14-10-2013, 11:44   #4
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

I experimented with deck placement when installing my Garmin.
It consistently got twelve satellites when placed ahead of my instrument panel ahead of the cockpit but behind the windshield.
I set it slightly off center so it wasn't under the boom.
It's completely out of the way. No problems with reception, ever.
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Old 14-10-2013, 12:03   #5
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

I haven't found any reception difference with the GPS receiver 10' up the arch with a clear view of the horizon or down in the engine compartment. Or in the cabinet under the chart table. The receivers on the new GPS's are very sensitive.

Of course, a steel boat makes a big difference on mounting one inside it.

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Old 14-10-2013, 12:13   #6
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

Quote:
Originally Posted by senormechanico View Post
I experimented with deck placement when installing my Garmin.
It consistently got twelve satellites when placed ahead of my instrument panel ahead of the cockpit but behind the windshield.
I set it slightly off center so it wasn't under the boom.
It's completely out of the way. No problems with reception, ever.
Ditto for me - I centered it.
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Old 14-10-2013, 14:30   #7
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

Mine is deck level inside the saloon. Amidships. Less rock roll and ptiching. Works fine.
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Old 15-10-2013, 09:57   #8
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Never on the Mast head. Low is good...short run on the coax..as all have said..the newer systems are more sensitive and perform well at previously unthinkable locations.....

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Old 15-10-2013, 17:45   #9
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

Yeah, what they all said.

Just in case there was any confusion based on the title of the thread, it doesn't make any difference because it supports WAAS. The old DGPS signal was VHF from a shore station and antenna height mattered. WAAS data is embedded in the satellite signal, so it's as good as the location data.
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Old 15-10-2013, 18:13   #10
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Agree I put mine below deck behind a removable ceiling panel. No issue. I did have a heat problem when the nmea cable joints were in the engine room. The heat in dead summer no wind constant motoring glitched the connection. Pretty sure that was the issue. I relocated the connection point and it has been fine. Big plus no cable going through the deck no weather sun etc... Exposure.
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Old 15-10-2013, 20:53   #11
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

Just one thing about low mounting to keep in mind.
Don't put it where anyone can sit above it, or even put an arm or hand over it.
You will lose ALL satellites until they move.
I found out this while experimenting with placement under a cockpit siderail.
Thankfully, it was just placed there, and no holes had been bored to finalize the mount.
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Old 15-10-2013, 21:04   #12
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I played around before fixing the mount below deck. Good point to try obstructing the reception. Some places were very poor. On the stern rail it might get a few more feet of accuracy.
So far it's very close to spot on. Given it has zero exposure to the outside its a nice compromise .
Can flip on the hd radar if in tight navigation area that needs confirmation.
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Old 28-10-2014, 01:28   #13
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

Hi all, can anyone tell me if I mount a gps antenna partially under a solar panel whether that will interfere with it working at all?
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Old 28-10-2014, 02:16   #14
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

Quote:
Originally Posted by Rustic Charm View Post
Hi all, can anyone tell me if I mount a gps antenna partially under a solar panel whether that will interfere with it working at all?
Modern GPS units are very sensitive and will still work satisfactorily with this sort of obstruction. However, the GPS is such an important instrument that I prefer to get the best possible information from it. It does make a (small) difference when high levels of precision are needed such as an anchor alarm or retracing a track, especially in conditions such as heavy rain.

I just tried my Garmin HH for you and the satellite signal strength went from 10 satellites visible with an average signal of 95% (from the unmarked scale) and a reported accuracy of 2m in open sky to still all 10 satellites visible with an average signal strength of 65% and a reported accuracy of 5m. This was directly under the centre of a solar panel.
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Old 28-10-2014, 03:05   #15
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re: GPS WAAS Antenna Location : Masthead or Sternrail?

Does anyone have firm data on GPS signal degradation when the GPS antenna is mounted on the mast head.

Clearly this gives the best view of the sky and clearly there can be some significant coax loss. The coax loss can be calculated and compensated for by using different coax or a higher gain antenna. I'm not convinced by the mast head movement argument with some firm data. Automobile and aviation GPS units seem to work quite OK in a highly dynamic environment.

But I could be persuaded by some solid data backing up the current viewpoint
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