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Satellites ?

Discussion in 'Pro/Adv Discussion' started by fastfed, Aug 21, 2016.

  1. fastfed

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    Since getting my drone back from DJI after stress crack repair, I noticed my sat. # has changed, from 17-20 down to 10-15.
    What is concerning to me, if I put my hand ontop of the drone, about 2-3 inches away, not touching it, but my hand covering the top back, satellites go to zero.

    Is there more then one GPS chip on this thing? is it possible they forgot to plug one in? This is enough for me to contact them and ask.
    What else could it be? maybe they installed it wrong? bumped it?
     
  2. whoreable

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    could just be a fluke, I noticed mine dropped to 0 with my hand on top once. Just be glad she has gps lock
     
    rkingsb353 likes this.
  3. Blue Bird

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    There is only one GPS module and it is adhered directly to the top shell center.
    Perhaps try moving to new a location. Use a GPS satellite tracker app to do a comparison.
     
  4. N017RW

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    As mentioned the GPS engine/antenna is centered in the top shell. It is to be expected that when covering this section with your hand that reception will be lost.
     
  5. Meta4

    Meta4 Moderator
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    That's completely normal (just like blocking the GPS antenna will block sat reception too).
    The satellites aren't fixed in space but are all in different orbits.
    The number in your sky is changing all the time.
    [​IMG]
     
  6. fastfed

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    This is interesting, but how often is that moving? if its monthly I would understand, but I doubt its monthly.. I fly at the same location at the same time, over and over ( I know boring )

    it just seems strange that my sat. # has changed
     
  7. Meta4

    Meta4 Moderator
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    The numbers visible anywhere are changing constantly.
    From one hour to the next you would see the numbers changing.
     
    HueJorgan and Techcop50 like this.
  8. fastfed

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    here is a screen shot, of shield tablet #1 and shield tablet #2, #2 is being used for the phantom and #1 is using an app to locate satellites

    DRONE#2 tablet
    [​IMG]


    SAT APP#1 tablet
    [​IMG]
     
    #8 fastfed, Aug 21, 2016
    Last edited: Aug 21, 2016
  9. Meta4

    Meta4 Moderator
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    Unless it was intentional, your Phantom is set to over expose and your images will look washed out.
    Use the right thumb wheel to dial it back from EV+1.3 to EV0 for proper exposure.
     
  10. WetDog

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    What does appear to be recent is the loss of GPS signal when you cover the top of the Phantom with your hand. This started out a couple of revs ago, maybe 1.5 or 1.6. It is unusual behavior because other consumer GPS modules seem to be more robust than that. My boat's 3 GPS receivers are under a fiberglass canopy and work fine. So does my iPhone. The P3, not so much.

    It is possible that, because it's an aircraft and DJI has more stringent requirements as to what constitutes a valid signal that it seems to be more twitchy. But I would hope Lowrance (who makes my boat electronics) would also be rather concerned with accuracy.

    But I think it was a firmware thing since it is consistent between all my P3s and didn't used to happen.
     
    mikesmiley likes this.
  11. fastfed

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    thanks, just seems weird, I will admit when I take off , I get more satellites, as you can see I am getting 11, after about 2 minutes sitting on the ground (this was not after a take off, I already landed, just popped this battery in to compare)
    It will sometimes get to 15, but it could and has dropped.

    I need to do more testing, so I won't worry myself yet, I also asked DJI their thoughts
     
  12. Vertigo

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    Fiberglass is transparent to RF signals . Human flesh (water/blood) is not. And neither is carbon fiber btw. Still, I agree its remarkable how quickly it loses all sats if your hand is above it.
     
  13. Dronason

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    On android, you can use app UAV FORECAST (UAV Forecast). The free version give 24h forecast for anything related to flying.
    It will use your location to indicate the maximum number of satellites you can see.
     
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  14. J&L

    J&L

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    I know back in May I was receiving 15-17 satellites and now I am seeing 12-14 in august. Maybe its that time of year just a guess really lol.
     
  15. Dronason

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    You can also use Location Lookup to retrieve for a given location / time what satellites can be at best seen.
    Don't forget it is as best value and there will be obstruction by buildings, tree, etc...
     
  16. N017RW

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    GPS signal strength on the surface is about -155dBW.
    That's 1e-13mW or 0.00000000000000001 Watts!!!
    It doesn't take much to block this signal.

    Here's a 3rd-party explanation:
    GPS Satellite Power Output

    Achieving more sats in flight is due to the horizon expansion as you climb.
    However this is limited by the antenna aperture and 'masking' where sats. near the horizon are ignored. Typically the mask is set about 5 deg. above the horizon.
     
    #16 N017RW, Aug 22, 2016
    Last edited: Aug 22, 2016
    Falcon900 likes this.
  17. Mocho

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  18. Ken Hanks

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    Solar activity has a huge influence on gps reception. Higher solar activity (Solar Flares) decreases the gps signal.

    Sent from my SM-N920V using Tapatalk
     
  19. Ken Hanks

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    Your comparing two different gps chips. Its like comparing apples to oranges. It would be more realistic to compare your signal with another identical drone.

    Sent from my SM-N920V using Tapatalk
     
  20. Dronason

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    That's true, this solar acitivity indicator Kp is also given by app UAV FORECAST (UAV Forecast).
     
    Ken Hanks likes this.