GP33 DOP

P

Pthein

Furuno Super Fan
What’s a normal / acceptable DOP? I’m getting 5.59 at times and slow acquisition... wondering if I have an issue with antennae, cabling, connectors or main unit itself. Or is this acceptable and normal?

I feel like preformance of GP33 should match closely GP330B but the 330 preforms awesome, GP33 is slow... maybe that normal.

Is there self tests I can do to see if I have an issue? What’s a normal DOP?

Phil
 
Pthein,

Where and how is the GP33 Antenna mounted..? Is it mounted in line with Radar Beam, or too close to another antenna..? The possible error source with the GP33 calculations could be due to a multipath effect. Multipath occurs when the GPS satellite signal bounces off of nearby structures like buildings and mountains. In effect, the GPS receiver detects the same signal twice at different ranges.

Here are the HDOP ratings:

1 Highest possible confidence level to be used for applications demanding the highest possible precision at all times.

1-2 Excellent. At this confidence level, all positional measurements are considered accurate enough to meet all but the most sensitive applications.

2-5 Good, Represents a level that marks the minimum appropriate for making accurate decisions. Positional measurements could be used to make reliable in-route navigation suggestions to the user.

5-10 Moderate. Positional measurements could be used for calculations, but the fix quality could still be improved. A more open view of the sky is recommended.

- Deep Blue
 
I’m assuming HDOP and DOP are the same. Manuals for GP330B speak of HDOP but the GP33 says DOP.

The GP33 antennae is mounted on the very top of my boat a good 10’ above the radar so that should be ok.

Other antennae’s mounted in the same area along with the GPA017 are a GP330B, Sirius antennae, cell phone booster antennae and TV anteanne.


Is there a way to easily determine if it’s a cabling/connector issue vs antenna issue? It’s not just low DOP but slow to acquire satellites and often can’t see any satellites when the GP330B is strong. The GP330B antenna is right next to the GPA017.
 

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Pthein,

I doubt that its a cabling issue, If the GPA017 cable was shorted you would not be getting any type of a Satellite signal, And since the GPA017 Antenna seems to be located in a good location, It could be that GP33 Display or the even the GPA017 Antenna could be defective.

I recommend in having a authorized Furuno dealer do a checkout the unit and antenna.

- Deep Blue
 
Having a cell booster anywhere near a receiving antenna like the Sirius or GPS is not a good idea. It sounds like the front end sensitivity is slowly going on the antenna. Replacing it will most likely result in the same thing repeating in a few years if it is getting blasted by a cell booster.
 
The cell boosting antenna is on an 18” pole and the GPA017 is on a 4” stub. Plus they are separated by ~20-24”. Would that still cause the issue?.

And are you saying the GPA017 could be damaged? Is there a way to test the GPA017?
 
The cell boosting antenna is on an 18” pole and the GPA017 is on a 4” stub. Plus they are separated by ~20-24”. Would that still cause the issue?.

And are you saying the GPA017 could be damaged? Is there a way to test the GPA017?
 
HDOP (HighRes dilution of precision) or DOP (dilution of precision) is basically the same thing. The best test of the antenna is to check this number as a direct reflection of good signal level. Normally in a good location, most GPS units will fall 1.9 or under HDOP/DOP.

Yes, you can damage your antenna. NMEA Standards recommend at least five feet distance; the more distance the better. Cell is in the microwave freq range as is your GPS and Sirius Weather antenna. Once the front end amp gets damaged on a GPS antenna it doesn't get better. It is like hearing loss when someone has been playing loud music into your ear, it becomes permanent. I see bad installs all the time walking up and down many of the docks. It is sad but most GPS antennas will go bad about the three year point if they are installed inside the beam of a radar or near other strong RF sources. That is exactly why NMEA and others have recommendations for this.
 
Just to close the thread we found a bad TNC connection in the back of the GP33. When we wiggled the connection we would loose and find satellites.

New crimp and solder TNC connection and we now acquire satellites within 10 seconds and never loose them just like the GP330B.
 
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