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How are drones getting the very long ranges RF? — Parallax Forums

How are drones getting the very long ranges RF?

T ChapT Chap Posts: 4,223
in General Discussion
I was curious about some drones and how they are sending live video for 3000 ft. Does anyone know what method of RF they are using to control something at that range and get data back? I wish there was a way to control a prop via RF like that.

Comments

  • Peter JakackiPeter Jakacki Posts: 10,193
    Cell phones work really really well from high up with a clear line of sight to many towers. That's a good reason to make them illegal to use on a plane because cell towers are designed to maximize the number of usable channels which goes out the door with thousands of phones high up chattering away to hundreds of towers on the same frequencies.. But in smaller planes and far out to sea I can get a good signal. So too with drones and a 4G modem or cell phone which will work wonders.
  • TubularTubular Posts: 4,702
    I think they generally use 5.8 or 2.4 GHz for bringing the video back, separate to the RF control of the UAV
  • W9GFOW9GFO Posts: 4,010
    I don't know, but I do know that they can transmit video from much further than 3,000 ft.

    The Mavic Mini is rated at just under two and a half miles. The Mavic Pro, over six miles.

  • Clock LoopClock Loop Posts: 2,069
    edited 2020-09-27 05:21
    20 mile (line of sight likely) 900mhz serial communication module.

    https://www.digikey.in/product-detail/en/laird-connectivity-inc/AC4490LR-1000M/AC4490LR-1000M-ND/1844881


    SUCK THAT BATTERY.
    650mA Transmit/Receive!

    Hope you can swim!
  • T ChapT Chap Posts: 4,223
    Thanks for the tips. I like that module, will keep it in mind future. 2x85$ is ok for some projects but too high for some. It looks like a more powerful version of the Nordic RF chips or Xbee. I’d like to find a 1000 foot cheaper version. Cell would be nice for some projects but what device allows cell>UART>prop data in both directions?

  • Duane DegnDuane Degn Posts: 10,588
    The high frequency stuff is often used for video because it has really high bandwidth. Lower frequencies have high range given the save power inputs.

    Have you looked at any of the many inexpensive LoRa devices?

    Andreas Spiess has a bunch of videos on this topic. Here's one of his videos.

  • Duane DegnDuane Degn Posts: 10,588
    iforce2d has several range tests of various type of radios. Here's a range test on a set of LoRa radios.



    Of course the range will be very different if there are obstacles between the radios.

    I used a set of 900MHz XBee modules and I walked down the street with a laptop connected to one of the modules. The other module stayed inside and just echoed whatever it received. The radios worked fine a block apart but as soon as I put a car or house between the two radios the connection greatly degraded.

    I think one reason drones get such good range is they're above obstacles which would block the signal.

    BTW, XBees generally work well but they're much more expensive than many other alternatives which also work well.
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