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Losing GPS lock

Are you having a problem with your DJI Phantom?

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Losing GPS lock

Postby Wight Wings » Mon Jul 29, 2013 7:40 pm

Been flying my Phantom for nearly 6 months without any major problems but I've encountered a strange problem over the last few days..

I’ll run through the procedure.
1.Turn on TX
2.Connect battery
3. Phantom goes through initialization / warm up
4. Green flashes as it set’s home point
5. Red flashes 3, 2, 1 and then none as the GPS connects to > 6 satellites
6. Green or yellow flashes depending on gps/atti

So everything is normal and you can leave it sitting there for as long as you like and it will remain connected to >6 satellites
However once you take off and after about 1-2 mins of flight i start to lose the satellite connection.
First 1 red flash, then 2 then 3 so it's losing satellite connections.

If you then land and kill the motors but leave the Phantom connected to the battery after about 20 secs it starts to reconnect with the satellites again. If you leave it sitting there no problem but once you take off again, after about a minute it start's losing the satellites again.

When it first happened i assumed it was bad weather conditions or some other temporary situation but it's been like this for 3 days now.

I’ve checked all the leads from the compass back to the GPS module and the GPS module it’s self but can see nothing wrong. Done advanced and compass calibration but still the same.

Ideas?
Wight Wings
 
Posts: 9
Joined: Sat Jul 13, 2013 3:39 am

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Re: Losing GPS lock

Postby halfpipe » Fri Aug 02, 2013 4:37 am

Are you still losing sat link?
Less than 20 short flights so I don't have any useful input but I've wondered about satellite density where I live on the east coast of Canada and other sparsely populated areas.
Which satellites does the Naza connect with and is there a chart showing their orbits or does it connect with geosynchronous birds and what are their positions overhead. I suppose latitude is a factor.
halfpipe
 
Posts: 94
Joined: Tue May 14, 2013 6:43 pm
Location: Atlantic Coast Canada

Re: Losing GPS lock

Postby Roadkilt » Fri Aug 02, 2013 10:59 am

Your situation as described happened exactly that way to me yesterday. I posted the video I made of the day on another forum, but here it is http://www.youtube.com/watch?v=TZLNK0sk9-c&sns=em

Anyway, I'm over water and in tough to recover areas so I'm very aware of the flashing lights. It did the same thing, on lift off it flashed a red light, new battery and gentle ascent so it shouldn't be a voltage drop issue. If anything it should have got a better sat signal as it was higher up. Anyway, I prepared myself for a going into atti or worse and watched it like a hawk. Back to green again.

Sunspots? No wifi where I was flying, clear day, full charge. I've read recent articles about GPS satellites getting dropped for various atmospheric and intentional reasons, perhaps that happens and it takes a second for that signal to be replaced in the chips selection of redundant sources. Disturbing to see when I'm over a waterfall!
Roadkilt
 
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Re: Losing GPS lock

Postby Roadkilt » Fri Aug 02, 2013 11:18 am

actually, in the video i just mentioned you can see it doing what you said at 1:32 into the video. I was flying into a canyon and it started flashing red! Yikes! Then it went green again. Maybe that rock wall cut off a sat, but where I started it up from was far worse for being blocked out and it was full green. Go figure.
Roadkilt
 
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Re: Losing GPS lock

Postby BruceTS » Fri Aug 02, 2013 12:13 pm

Roadkilt, GPS is tricky, going into the canyon the signal can bounce off the walls, probably why it was all green.

As for the OP, have you taken off the top cover and checked to see if you have a loose connection?

Dropping a sat or 2 is normal for GPS, but usually you'll pick up a few as well...
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Location: Granada Hills CA

Re: Losing GPS lock

Postby Wight Wings » Thu Aug 08, 2013 6:43 am

BruceTS wrote:Roadkilt, GPS is tricky, going into the canyon the signal can bounce off the walls, probably why it was all green.

As for the OP, have you taken off the top cover and checked to see if you have a loose connection?

Dropping a sat or 2 is normal for GPS, but usually you'll pick up a few as well...


I had been working on my Phantom for about a week trying to sort the gps siltation out so yes the cover was off and on numerous times a day and everything was checked many many times..

In the end i started backtracking by removing my upgrades which included the v2 pmu, the additional fpv camera, the fpv transmitter ect. I ended up with a stock phantom but still had the problem..

I then removed the copper tape that i had stuck to the foam/copper shield that's stuck over the GPS/compass module.. The reason for using some additional copper tape was to 'in theory' increase the shielding from interference but for some reason it was making it worse as when i removed it my GPS lock problem suddenly got a lot better..

I then replaced all my upgrades and install a couple of Toroids on the GPS lead and main power lead and everything now seems ok again..
Wight Wings
 
Posts: 9
Joined: Sat Jul 13, 2013 3:39 am



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