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I Drone Gun

  1. Aug 12, 2017 #1
    A company named Drone Shield has developed a 'Drone Gun', which is capable of jamming a drone from up to 1.2 miles (approx. 2 km) away.

    https://www.washingtonpost.com/vide...1749443c5e5_video.html?utm_term=.2db123e1e5b2

    I am aware of how the jamming works, where the gun emits frequencies of 2.38Ghz-2.483Ghz and 5.725Ghz-5.825Ghz, which are the most common frequencies a drone operates on. Consequently, this causes the drone to think it is out of range, hence activating its safety system and slowly descending to the ground.

    However, I am not entirely sure how the radio wave is focused and directed towards the drone

    The following image shows a front on view of the gun, http://imgur.com/a/tB7oM
    I've labeled what appears to be the source of the directed radio waves.
    Does anybody know what type of directional antenna is in these three labeled pieces of the apparatus? I'm unsure whether they'd be high gain yagi directional antennae or helical antennae.

    Also, If anybody is able to offer an explanation of how radio waves are focused and directed into a 'beam' as well as how the distance is increased, this would be much appreciated :)
     
    Last edited: Aug 12, 2017
  2. jcsd
  3. Aug 12, 2017 #2

    davenn

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    Clipboard012.jpg


    there will be high gain Yagi antennas in one or more of those oblong casings

    pretty straightforward technology ... a Yagi for each band of interest ... one in each casing

    by the use of yagi or other directional antennas like dish antennas as used for satellite TV
     
  4. Aug 12, 2017 #3
    All the principles you know from optics apply. Radio waves differ in having inconveniently large wavelengths and conveniently slow frequencies that are accessible by electronics.

    The dipole oscillators which produce light are atomic sized. The dipole radiators which produce radio waves are most efficient if they are 1/2 wavelength long (usually two 1/4 wavelength long rods end to end). The frequencies you mention have wavelengths of ~12 cm and 5 cm, so you can expect short rods of 6 cm and 3 cm respectively. With just one emitting rod you get a dipole pattern which is strongest in the directions perpendicular to the rod.

    The Yagi antenna mentioned above uses several of these dipole emitters in a row. Actually only one is actively driven and the others are driven by the field from the first, but you can think of them as a row of emitters. The principle that results in the emission being directional is interference. This is analogous to a diffraction grating in optics. The distance between the emitters is chosen so that the emitted field is exactly in phase in the direction along the line of emitters. As you go away from that line the emissions are more and more out of phase and cancel. This results in a strong diffraction lobe in the forward direction.

    Another way to direct a radio beam is a dish antenna. This works exactly the same as a parabolic mirror in optics. However the collimation of the beam is proportional to the wavelength (see diffraction limit) so a dish reflector for radio waves has to be inconveniently large. For example if you wanted to concentrate the beam into 100 mrad to pick a random number, your 12.5 cm wavelength would require a 40 cm aperture.
     
  5. Aug 12, 2017 #4

    anorlunda

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    I believe that radio jamming is highly illegal in the USA, regardless of the purpose.

    Theaters would love to use cell phone jammers but it is not allowed.
     
  6. Aug 12, 2017 #5

    berkeman

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    Yes, radio jamming by unlicensed private citizens would generally be illegal for several reasons. Law Enforcement has several new technologies that they are using to try to deal with rouge drones, and that might be a valid subject for a different thread.

    The OP's question has been answered (highly directional antennas are used), so this thread will be closed now. Thank you all for the quality replies.
     
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