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Satellite count fluxation?

Discussion in 'General Discussion' started by rwebcon, Sep 11, 2014.

  1. rwebcon

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    I’m flying the phantom V2+ at about 6500 feet in large open area soccer field and getting funny satellite counts. I will start out with a good satellite count of 7 or more and fly for about 8 minutes then start to see red LED’s. The count will go from 6 to 4, then 6, then 7 or more than 4 back and forth with different count but once this starts it seems to get worse. The distance from home is never more them 40 to 50 feet at a height of no more than 50 feet. Has anyone else experience this? Any answers to why the fluxation in satellite counts? Could the GPS mod be marginal?
     
  2. ProfessorStein

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    K-index? :D

    But seriously... are you seeing this every time you fly, or just certain days?
     
  3. 480sparky

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    Contrary to some beliefs, GPS satellites are NOT in geosynchronous orbits. They move across the sky, in orbits 55° to the equator, with periods of or slightly less than 12 hours.

    Therefore, while you are flying it could well be that some of the satellites being received start to dip below the horizon.
     
  4. HarryT

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    That's very true, but if you're flying in an open space, 4 satellites isn't normal. I normally get somewhere from 9 to 11 here in the UK.
     
  5. ProfessorStein

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    You do, however, hope that there are a minimum of 7 to 8 satellites in "view" at any one time, though, regardless of which satellites they may be.
    The whole GPS system kind of relies on that fact. As one satellite exits the hemisphere, another one (or more) is supposed to enter in it's place. It should never dip below the minimum... especially on a clear day, in an open unobstructed field.
     
  6. Meta4

    Meta4 Moderator
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    Check with a handheld GPS or a GPS app on a mobile phone to see how many satellites really are in your sky.
    Compare that with what your Phantom sees.
    If there is a big difference, there is interference (I mean internally) or a fault in your machine and you need to fix it.
     
  7. rrmccabe

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    One thing not mentioned that I am going to toss out. Are you starting and stopping video at all during this time?
     
  8. rwebcon

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    I'm not starting or stopping video during flight. Does this happen often at this site and the answer is no but I have only been their three times.
    As suggested I will take my Garmin with me next time and check for number of satellite, great idea.
     
  9. rwebcon

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    Update:
    Just ran a test outside with Phantom and Garmin Montana. The Garmin shows from 8 to 11 satellites with varying strength(all above 50%) but the Phantom signals red red green at 5 and does not change over a few minutes. Does anyone know the requirements on satellite signal strength for the Phantom to use the signal? For example does it have to be say 80% or above all the time before it will use it? If one fades out will the Phantom quickly pick up other and still signal over 6 satellites(transition time)? It may be time to open it up and replace the GPS mod.
    Thanks everyone for you help and advise.
     
  10. ProfessorStein

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    I use an app on my phone to check the number of satellites pre-flight, and it consistently reports 2 or 3 satellites more than my Phantom 2 Vision and the Vision app do at take-off. I just always figured it was because the Phantom's GPS puck is tucked inside the shell. This can, arguably, be verified by the folks who have increased their GPS performance by adding the reflector mod inside the shell. And I would imagine the Garmin is even more sensitive than my phone is... which would mean it's number (and the difference) might even be higher.

    So tell us about the environment you are setting up in. What kinds of obstructions are around you?
     
  11. Meta4

    Meta4 Moderator
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    The internal electronics of the Phantom interfere with the GPS signal.
    DJI made an attempt to shield it but they were not totally successful.
    The fix is easy and many have done it with very good results.
    Recommended for all to improve GPS reception.
    viewtopic.php?f=27&t=19099
     
  12. rwebcon

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    My first post give the flying environment. I did try the tin foil cover to no avail. But it did pickup signals if I held the cover up a few inches above the phantom.
    I think the mod maybe bad.
    How is the DJI support on return to fix problems?
     
  13. RIDETOEAT

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    If your GPS module is bad DJI will fix but known to be pretty slow. If your GPS signal is poor when plenty of sats are available then you need to re-look at your aluminum foil tape mod, again, did you move the module wire to route under the OEM shield and shield the wire itself all the way to the plug, then line the interior of the shells middle area with the aluminum ducting tape. I had amazing results from this and I would estimate from reading many entire threads about it that more than 90% of the people do. It is a 30-40 minute deal and much more effective than anything DJI will do for you as I doubt they are adding shielding to Phantoms that come in for service with low sat. reception. You certainly should not have to do it your self but it works so well it is worth the small effort 10 fold. My sat count doubled from 5-6-7 to 11-12 commonly now and never more then 1 sat drops off when I go into record video mode. Most of the time it holds.
     
  14. rwebcon

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    I used regular house hold foil and did cover the rerouted connector under the original shield. I may try the tape it is much thicker.
    Thank everyone for your input.