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Homebrew radar?

Discussion in 'Misc Electronics' started by steamer, Aug 31, 2007.

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  1. steamer

    steamer Guest

    --Lotsa links for police radar but I need a 'real' system that can
    image objects over a range of several hundred feet and present this info on
    a display. Has anyone seen kits/plans for something like this? The cheapest
    off-the-shelf unit I've seen is more than $2k and my pockets aren't that
    deep...
     
  2. Eeyore

    Eeyore Guest

    $2k sounds like a bargain.

    Graham
     
  3. steamer

    steamer Guest

    --None really useful
    --Yes, dear.. Shooting in the dark at the moment because it's just
    an idea at present but I suppose ideal output would be to a laptop computer
    display. The problem is to image pedestrians, bicyclists and other vehicles
    within a range of, say, 400ft, that may stray across my route, so figure a
    cone of view of maybe 45 degrees either side of centerline. Resolution: if I
    can see a pedestrian as any sort of blob on the display that's good enough.
    Weight isn't an issue as it'll be mounted on a vehicle; i.e. a hundred
    pounds of stuff is acceptable. Power would come from a 12-v car battery or I
    could use a 2kw genny. Ultrasonic might be doable but again I haven't got a
    clue, which is why I'm asking questions! Yes, I could build from schematics;
    I'm a machinist by trade so I can also fab most anything in the way of
    mechanisms needed for the project. The goal is to come up with something
    that could be released into the wild so that anyone in this predicament who
    desired such a system could build their own. What have I left out?
     
  4. steamer

    steamer Guest

    Labor I can discount; what parts are needed? That's the main
    question.. Being a machinist I can fab a lot of stuff from scratch, but the
    electronics end of things has me baffled.
     
  5. steamer

    steamer Guest

    --Following up my own query. Made a trip down to HSC and talked to
    the gang. The major problem with radar seems to be a legal one, as it is,
    basically a high-powered transmitter which requires licenses I don't have to
    operate. So plan B seems to be using other portions of the spectrum. Various
    ideas put forth included:
    -Sonar which, although intended for water, can be made to work at
    ultrasonic frequencies in air.
    -FLIR seems to be a winner as there is hardware available surplus.
    Apparently Cadillac offered a FLIR, complete with a HUD (for imaging in rain
    and fog) for two model years so maybe I can get lucky at a good sized
    junkyard.
    -One wild idea was LIDAR but I wouldn't have a clue where to go with
    that one.
    Thanks to those of you who offered *useful* info...
     
  6. Eeyore

    Eeyore Guest

    Frankly I doubt you can even source the required magnetron as a 'hobby' item. Do
    you plan to make your own radar dish too ?

    Graham
     
  7. Eeyore

    Eeyore Guest

    I have my doubts that a microwave oven magnetron is suitable for providing the very
    short pulses required for radar. Talking of which, 'the modulator' that pulses the
    magnetron supply will be another very difficult design.

    Graham
     
  8. big.rad.maps

    big.rad.maps Guest

    Steamer, I think your question goes beyond the current state of the
    art - at any price.

    RADAR needs to be scanned to build up an image (linear image with a
    circling antenna or 3D image with a more complicated 2D scanning
    antenna, or with an electronically steerable antenna array). None of
    these are labor intensive devices (unless you can machine a small
    antenna with fast 2D scanning abilities). You will eventually hit the
    need for lots of electronics and computing power.


    As an aside, I think it was an engineer at Lockheed that bolted a
    bunch of TV antennas to an outside wall here in Gaithersburg MD, about
    10 years ago and processed the signals to generate radar like images
    from aircraft and other items in the area. TV stations and Radio
    stations put out hundreds of kilowatts from stationary antennas, and
    that RF signal bouces off of remote objects and comes back to the
    passive listener.

    Passive RADAR issues:
    -low frequencies/long wavelengths mean large antennas - Lockheed had
    an outside wall decorated in antennas.
    -some TV transmitters might go up to 600 MHz, so smaller antennas are
    possible. Cell phones go from 875 MHz up to about 2 GHz.
    -your antenna might be an array of small antennas but then you have to
    electronically switch, amplify, receive and process multiple streams
    of signals
    -processing each signal to detect fractional differences in arrival
    time which would then indicate direction of signal (in 3D) is compute
    intensive. I.e. you are trading receiver simplicity -- passive
    antennas -- for computational effort (this is why radar dishes swivel
    - they assume they are only looking at the single transmitter source
    in one direction, and distance is determined by the time it takes for
    the signal to reflect back to the antenna)
    -You cannot generally detect living things with RADAR. The reflected
    energy is going to be small, and you will need more dynamic range
    (small reflection and hence more processing power or larger antennas)
    to identify these living things. (Maybe flocks of birds at airports
    are one of these cases where living things are detected)

    The new terahertz radars are interesting, in that the wavelengths are
    so small that at least in theory you could fit an entire antenna array
    in a handheld device, but that's in the far future.
    http://www.space.com/businesstechnology/technology/t-ray_camera_020613.html

    Cheers
     
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