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Losing GPS lock in flight

Discussion in 'Phantom 1 Help' started by toddtt, Sep 30, 2013.

  1. toddtt

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    Hello,
    I bought my Phantom from Dronefly about 2 weeks ago. I love it but it has just developed a problem. After a normal start-up, no red lights and after home spot has been marked with the rapid green lights – the phantom flies normally in GPS mode with no problems. However when I climb the unit up to about 80 feet or so, it loses satellites and I get the red lights. Sometimes just one, sometimes two or three. When this happens the phantom will not hold position and flies like it is in ATT mode. There are absolutely no obstructions to the sky. There are no power lines nearby. There are no large buildings at all. When I bring the phantom lower (around 30 feet) the red lights go out and GPS mode works fine. This condition happens every time I fly. I have upgraded the firmware to the 4.0 per the instructions and also performed numerous compass calibrations and basic and advanced IMU calibrations. No change. Any ideas?
     
  2. Gizmo3000

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    Location:
    Sherman Oaks, CA
    Just to be sure, when you climb up to 80 ft, does it continue to blink a red light while hovering at that altitude?
    or only while climbing?

    If you've been flying for awhile, and the battery is closer to being empty, it's normal to get some red blinks while the Phantom is under load (while climbing).
    It's also normal for it to drift a bit more while higher up, where there's more of a breeze, so it's slightly possible that's what you're experiencing.
    But if you're in GPS and it wanders more than 7ft or more in any direction, under little wind, and the green+red blinks continue, sounds like you might indeed be experiencing some issues.
     
  3. toddtt

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    Thank you for the reply. I should have mentioned...this happens with a fresh battery, right after initial takeoff. I am familiar with the low batt red light and understand exactly what you mean about the "temporary" low battery light that will come on when you are close to an empty batt and "throttle up" to climb. As far as the drifting...when it looses the gps it definitely will blow away with the wind and keep going until I correct it. Just like in ATT mode. I read elsewhere on the forum about cracked GPS antennas. I have had one minor crash where I go to close to a pool screen enclosure an it fell 2 feet into the grass. But I am almost certain this weird stuff was happening prior to that. I am going to open it up today and look at the GPS.
     
  4. jumanoc

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    You are on the right way. It points to GPS / Compass error (they work both together on phantom).
    Check these:

    1) Tight connection in wires going from compass to phantom (both extremes)
    2) Tight connection in wires from GPS unit toNaza FC (some bumps can unfit it)
    3) Uncover carefully the GPS unit and verify cracks on GPS itself (ceramic area) and /or bad or loosen soldering points.

    [​IMG]

    [​IMG]
     
  5. toddtt

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    Thank you both very much. Ok - I opened it up today and checked everything. All plugs/wires looked good but I disconnected/reconnected them anyway. I inspected the GPS antenna and it looked perfect. I took it out and I had the same trouble with the loss of signal. On a hunch I landed and walked about 50 yards from where I have always taken off from at the edge of my driveway. I haven't taken it anywhere else since I bought it. I started over (rebooted) and guess what? It worked perfect - no red lights no matter how high I climbed. I had this hunch because I after some experimenting I realized that the GPS red lights would come on in almost the same spot in the sky every time. I thought that was just to much of a pattern to ignore. So the next thing I tried was flying to that spot from my new launching spot to see if the red lights would come back. They did not. So it appears to me that there is some sort of interference (perhaps compass) at the edge of my driveway which at altitude cause the GPS to drop out. Move down the street just 150 feet or so and I flew 4 batteries with perfect flight behavior. I plan on doing some more diagnostic flying but I think I am on the right track.
     
  6. miskatonic

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    Time of day may affect GPS coverage. I noticed that I get better and faster GPS coverage when I fly at certain times of the day.
     
  7. UTR

    UTR

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    My phantom looses gps lock for a second or two if I climb really aggressively but they it immediately reconnects this is pretty normal. As for it drifting do an advanced IMU calibration your system might say it doesn't need it but do it anyway. Depending upon how windy it is remember 80 feet up the wind will be totally different as it's not being blocked by trees and building you might get blown about a bit. I have video recorded from my Phantom whilst it's just sat with the GPS holding it in position and it has to lean into the wind at quite an angle you'd be surprised how blowy it can get.
     
  8. jumanoc

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    Those are not GPS looses, those red lights are caused due your battery is having a big discharging request when you push the throttle too high. Don't worry while lights return to GREEN ;)