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Long range flying- which signal do you lose first?

Discussion in 'Phantom 2 Vision + Discussion' started by Foosy, Oct 27, 2014.

  1. Foosy

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    Trying to make sense of losing the signals on long range flying.

    The app is connected to the range extender over the 2.4GHz channel. That means that all the telemetry info and messages are provided through this channel. The control signal is sent through the 5.8GHz channel, so if the phantom loses this signal the reporting has to be done from the phantom through the telemetry data on the 2.4 channel because the 5.8 channel does not communicate at all with the app.

    We have 2 scenarios.
    Scenario 1: control signal lost first. With this scenario, the message can be relayed back to the pilot through telemetry. But, if the control is lost, doesn't the phantom return home? Which means it will get closer to you so how can you have a situation where you will later get a message of connection broken? In other words: we cannot fly the phantom further than the control signal lost point, so how would we would get a connection broken???

    Scenario 2: FPV lost first (phantom connection broken). If we lose telemetry and FPV first then even if we flew the phantom further away, how would it be able to let us know when it reached the point of losing control signal? Wouldn't it just return home without a message being sent? And if it was already returning when the FPV was resumed, wouldn't it just say returning home?

    Is the telemetry being broadcast separately from the video, so that it may still work at a smaller bandwidth After losing FPV?
    If yes, is the telemetry signal capable of a longer range than the control signal? Is there a third message if we lose telemetry signal?

    Also curious as to why dji decided to use two separate channels. This requires more hardware, and more antennas and has more points of failure. The control signal is low bandwidth in the direction from controller to bird. The FPV a and telemetry signals are higher bandwidth but in the other direction. Why not have all signals travel on one wifi network? It is not like the transmitter/receiver can't handle this. You can for example stream a movie to your laptop and at the same time play a multiplayer game, requiring bidirectional communication.

    Finally, instead of setting a fixed FPV streaming bandwidth, why not have the resolution dynamically adapt to the quality of the signal? Or if dji does not want to have a fancy algorithm, they could have the streaming resolution be a function of the distance. These parameters are always known. Did dji get lazy and chose to use two systems because it was easier to slap a standalone video solution?

    I would prefer one wifi mimo transceiver; one set of antennas and dynamic signal adaptation.
     
  2. Dirty Bird

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    I think DJI chose this system because it was the most cost-effective solution. Separate frequencies for control and FPV is the norm. There are specialized single-frequency solutions...DJI's Lightbridge is an example. It combines everything into a 2.4 Ghz system, but the system alone costs $1400! Personally I'd like to see them go with a cellular or satellite broadband solution. Range limited only by battery power! :cool:
     
  3. aseidman

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    Adding a cellular connection would be a huge step forward. Seems so obvious that I suspect it's less of if rather a question of when they do it.
     
  4. Foosy

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    Bumping my own thread as I didn't get a response on my original question.
    How can people claim that they are getting both signal lost messages if they continue to fly the bird?

    We have 2 scenarios.
    Scenario 1: control signal lost first. With this scenario, the message can be relayed back to the pilot through telemetry. But, if the control is lost, doesn't the phantom return home? Which means it will get closer to you so how can you have a situation where you will later get a message of connection broken? In other words: we cannot fly the phantom further than the control signal lost point, so how would we would get a connection broken???

    Scenario 2: FPV lost first (phantom connection broken). If we lose telemetry and FPV first then even if we flew the phantom further away, how would it be able to let us know when it reached the point of losing control signal? Wouldn't it just return home without a message being sent? And if it was already returning when the FPV was resumed, wouldn't it just say returning home?

    Is the telemetry being broadcast separately from the video, so that it may still work at a smaller bandwidth After losing FPV?
    If yes, is the telemetry signal capable of a longer range than the control signal? Is there a third message if we lose telemetry signal?
     
  5. jwegener

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    Not quite sure what you're asking. FPV/telemetry are one in the same (2.4ghz). And your control signal is another thing (at 5.8ghz)

    If either cuts out, your drone knows that -- it detects that and triggers RTH (and it ignores all control signals being sent to it). I think your question is how would your phone know what's going on?

    Well if you lose control signal, your phone sends back via FPV the fact that it's lost control signal and that its returning home. In the other case, where you lose FPV, it doesn't show RTH on screen immediately (despite it being triggered and the drone starting to return home). The screen instead shows "phantom connection broken" and turns grey and looks disabled. Once the drone gets back into range the FPV comes back and the screen comes to life again and shows that your drone is returning home to you.

    Does that answer your question?
     
  6. Idbird

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    :D I'm not a super long distance flyer, but usually the 2.4 ghz wifi drops first. Most times it will get glitchy before you get the phantom connection broken message. The bird will not automatically return to home when you lose wifi. In that scenario, I switch to home lock and reel the bird back and regain connection. You won't get telemetry or video feed until the wifi reconnects.

    In your first scenario, where the 5.8 ghz control signal is lost first, you won't be able to fly any further or control the return to home which will happen 3 seconds after the signal is lost. That's when you see the coming home message.

    I hope this helps!
     
  7. flyNfrank

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    I think I have the answer you're looking for.

    The examples you describes can both take place if using one of the aftermarket apps. From experience, I have had say the Lost Connection message come on as I was climbing altitude and remain viewable while I continued my ascent. If I tilted my hands some to where the wifi icon came back on, it would then stop displaying the message. This taking place adds to my theory that there is preset points set in the software by way of value numbers. Until I can get someone to read the amount of power coming out of the antenna, this theory has to be considered speculation.

    Back to your scenario's, the above is the only I know of that our quads will continue flying after the messages are displayed. And there is no speculation to this either.
     
  8. Foosy

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    My question was how come people have described in other posts getting BOTH messages in the same flight?
    My assertion was that you will get only one of the two messages, depending on which signal cuts first.
     
  9. aristosv

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    99% of the time you will loose the 2.4GHz signal first. In which case you will get a message saying "connection to phantom lost". That simply means that you dont have video feed on your phone. But you can still control the phantom.

    When doing long range i usually loose the video feed, but i keep pushing the phantom away. At some point and only for a few seconds i get he video feed back, and see that i have actually covered more distance while i had no video feed.

    In the unlikely scenario that you loose the 5.8GHz connection, you will see a message saying "control signal lost". If it stays like that for a few seconds, then the "coming home" message will appear and the phantom will head back to you.

    My experience with the phantom has shown that the problem will always be the video feed. Thats the part to strengthen if you want long range.