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Can water interfere?

Discussion in 'General Discussion' started by Narrator, Dec 19, 2014.

  1. Narrator

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    Hi,

    Can flying over water interfere with the video signal?

    I've been trialing my new Phantom at a nearby sports ground. Yesterday I found a small swampy lake beside the ground, so I flew over it as I stood next to the lake. The preview picture on my phone froze a few times as I flew over it, even though I was only about 10 to 15 feet away. During the 3 or 4 minutes over the lake, it froze 3 times for maybe 10 to 20 seconds each time. There were a few trees either side, but nothing between me and the Phantom. I still seemed to have full control, and once I flew away from the lake it was all good again.

    [​IMG]

    It only happened when I flew over the reedy parts, not over the open water.

    When I viewed the video later, it was all captured ok.

    Cheers
     
  2. Great Pumpkin

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    Weird! Maybe some water trolls have some sort of ray gun.
    Have you flown this path several times on different days, and if so, did your Phantom react the same way each time?
     
  3. Narrator

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    No.. first and only time over this pond. Maybe there's a UFO buried there.. lol
     
  4. Great Pumpkin

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    Go fly it a couple more times - see if the phenomenon repeats - go at the same time of day, same weather if possible.
     
  5. PhantomFanatic

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    Although water can affect RF propagation, such as mounting a tower in a lake. (I've seen such for an AM station.)

    But, flying at that height above water, shouldn't degrade the signal. Try flying at higher heights and see if there is a pattern. I doubt not, but that would be an interesting experiment!
     
  6. Narrator

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  7. ianwood

    ianwood Taco Wrangler
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    Water can and sometimes will cause a range of interesting anomalies with RF signals. There are a lot of factors involved in determining the impact.
     
  8. sdtrojan

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    Water can and sometimes will extinguish fire.
     
  9. djsydvicious

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    I'm sure you had your WiFi Extender pointed properly for such a close controller to drone distance but I thought I'd just type this anyway...
     
  10. djsydvicious

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    Out of curiosity, what is the lowest altitude you would/should consider flying over water?
     
  11. Narrator

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    Update:
    I flew over this water again yesterday. The same thing happened - the preview screen froze over the reedy parts.
    When I viewed the video later, over those parts of the lake, I noticed faint scan lines, like you used to get on the old tube tv when there was radio interference.

    FWIW, here's my 2cents on that.
    I would test the water, so to speak, before filming anything - make sure nothing will interfere. On calm days, you should be steady maybe 3 feet (1 meter) off the water. Experienced people often seem to go lower. But on windy days, height stability is a little compromised as the quad fights the wind and the gusts.

    In my short time owning one, flying and filming every day for a week, I've done a few hrs in strong winds. As it fights the wind and the gusts, it can oscillate 3 or 4 feet from it's hover height. And when moving, it can fluctuate even more. When you move, you're basically lifting the quad in the direction of flight, which makes a little height change inevitable.
     
  12. Meta4

    Meta4 Moderator
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    Striped sky is usually what happens when you are looking towards the sun - caused by shadows of the spinning props falling on the lens.
     
  13. Narrator

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    This was consistent across the whole screen.

    Here's the video.. not as clear as the original, but still quite visible, especially on full screen.

    [youtube]http://www.youtube.com/watch?v=oXCVnHSnKlw[/youtube]
     
  14. Nidge

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    Those lines you are experiencing are caused by the shadows of the props as you fly toward the direction of the sun. They can be reduced with the use of a Neutral Density (ND) filter.

    As for strange anomalies over water. At the frequencies used on the various Phantom bits water is a very reflective medium. When a radio wave is reflected its polarisation and phase are altered. As well as receiving the wanted direct wave you will also receive the unwanted reflected wave. If the phase of the unwanted reflected wave is shifted significantly with respect to the wanted wave, at the most extreme 180 degrees, then the added sums of the two waves will cancel out and the result is a very degraded or no signal response. That's why some receivers have two antennas (diversity reception) to mitigate this cancelling effect.

    On a recent Multirotor Podcast the pro-flyer in the studio urged listeners not to use GPS hold when flying over largish bodies of water but instead to use ATTI hold as there is a high risk, dependant on changing environmental factors, that the simple GPS units fitted in multirotors could be easily confused.

    Regards

    Nidge
     
  15. Khudson7

    Khudson7 Guest

    HA, HA, made me laugh...seriously though, I have flown over water many, many, many times at all levels without incident. I would suspect something else weird might be going on there...just IMHO. like a haunting or worse...phantoms. Try flying over water someplace else and see if it happens.
     
  16. Narrator

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    Cheers, and thanks for the other info too.

    Is there an electronic version of an ND filter? Can't fit a real one to the V+
     
  17. Happyflyer

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    I have seen these many times in my videos. If not going to use a filter, does anyone have info on a lens hood fixing this problem?
     
  18. Fplvert

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  19. Happyflyer

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    Looks interesting.
    Thanks.
     
  20. AndysAdventures

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    I've been flying low over water almost every time I take out my V+ and I've never had a problem with the video dropping out.

    Check out this video of fish jumping - [youtube]http://www.youtube.com/watch?v=iIEk6xI8W2s[/youtube]