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Erratic Satellite Lock

Discussion in 'Phantom 2 Vision + Discussion' started by MapMaker53, Oct 31, 2014.

  1. MapMaker53

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    I have a site that I will need to fly using the GS feature, so last night I decided to play with the GS having never flown that way before. It was dark out, so I just wanted to simulate a run through with the bird sitting on the backyard table and props off. To my surprise, I only had 5 sats showing last night when I have never had less than six since I bought it last May. I then noticed the count was fluctuating every second or two between 5 and 3 sats, with a brief 6. So I couldn't play with the GS.

    The erratic nature of the number of sats detected really surprised me. The sky was perfectly clear. I had flown a large site on Monday with absolutely no problem at all with a consistent 8 sats. Never had a crash and have been hand catching. Is it possible most satellites that night were near the horizon and I was picking up weak signals? Walking it from the back of the house to the front yard and turning the bird in different directions made no difference. I'll try it again today at lunchtime.
     
  2. Nathan Carter

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    When you test satellite reception, always compare between tests executed at the same time of day!
    [​IMG]
    GPS satellites complete their orbit in 11 hours and 58 minutes. So approximately every 12 hours they are at the same position on the sky.

    There is also space weather to be taken into account, disturbance of Earth's magnetosphere caused by solar winds. Check if the k index is high:
    http://www.swpc.noaa.gov/rt_plots/kp_3d.html
     
  3. Nathan Carter

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    Actually now that I think about it I'm not sure if the same constellation of GPS satellites is visible at the same time of day. They say on wikipedia that orbiting time of the satellites are 11:58h but what about Earth rotation. Not too sure, maybe someone smarter here can explain!
    From my experience with the Phantom itself, everyday around noon I only get 5-6 sats and that after a long wait. Same location in the afternoon(5pm), immediately 8 sats and more.
     
  4. GustavL

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  5. N017RW

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    It's a good indication of general 'visibility'.
    Don't expect exact correlation.

    What I have found interesting about that site is repeatedly selecting days into the future and watch the peak visibility numbers shift 'counterclockwise' or to the left.
     
  6. Meta4

    Meta4 Moderator
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    Instead of guessing, use a handheld GPS or the GPS status app to see what sats are in your sky and see a plot of where they are. Compare what's there with what your bird reports.
     
  7. MapMaker53

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    The k value was low last night and I can understand the different sat counts at different times of the day depending on their location. What has me concerned was the changing sat numbers literally from one second to the next on the screen - back and forth as though cycling. Thought it should be fairly stable. Has anyone seen that?

    I don't own a handheld GPS unit with a satellite counter. But I'll check into a GPS status app for my Galaxy tablet. Thanks.
     
  8. Mako79

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    You can't compare sitting it on a table vs aibourne.
    If you care comparing sat counts, it must be at the same time and location.
     
  9. MapMaker53

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    Well I just tried it again and this time I got a nice solid 9 sat lock. Not sure why the constant fluctuation last night but at least I feel better that the GPS module hasn't crapped out on me.
     
  10. ToThePoint

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    Yes i have seen that.
    Check your GPS module ASAP.
    There is a reason for this behavior and i had it due to a faulty connection in the module.
    Check everything on it.
    I mean really everything !!!

    I had a really hard crash due to it so be very vigilant.
    It started doing the sat dance after the motors were turned on.
    In idle/startup up it was stable @ 10/11 sats. ones the motors were turning it dropped to 7/8 and in flight 3/6. Alternating rapid between 7/8 to 3/5 and back.
     
  11. MapMaker53

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    Thanks. I'll check it out before I fly again. Mine was fluctuating with motors off. No change when the motors were turned on. That was last night.

    Would anyone have a photo of the GPS module and what connections might be loose? btw.. I also had done the wire shielding mod back when I first got the bird.