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Radar/Radar Gun questions

  1. Jul 24, 2010 #1
    Hi guys, I have a couple of questions,

    1. Is a FM transmitter for an Ipod the same thing as a FM transmitter and Reciever for a radar gun?

    2. Where can I find FM transmitters and Recievers for a radar gun. Or even better parts or a kit to build my own radar gun. (link would be helpful)

    3. What objects can radar travel through

  2. jcsd
  3. Jul 24, 2010 #2
  4. Jul 24, 2010 #3


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    Frequencies used for FM are not the best for Radar use (wavelengths are far too long). In any case, you need type approval to operate any Radar system so you shouldn't build anything yourself although you can buy relatively cheap marine (and probably airborne) radar equipment.
    You can, however, detect objects, such as aircraft, by the multipath interference (beats) caused between direct broadcast signals and reflections from the aircraft. That was what the first experiments in radio detection of objects were based on.
    Optical frequencies are not controlled by the authorities so you could make a system based on a modulated laser beam.
  5. Jul 24, 2010 #4
    I only need something that can detect a car that's 10 meters away, find out its speed its coming at me with and its distance from me. So I was wondering if there's anything out there than I can use to do this. The smaller the better.

    It would be even better if its just like a couple of small computer chips. What I need is...

    1. Something to transmit radio waves
    2. Something to receive radio waves
    3. Something to compute the radio frequencies to "MPH and Distance"
    4. Something to transmit that data wirelessly to a main computer.
  6. Jul 27, 2010 #5
    A quick Google search turned this up as the second item in the search.

    << link deleted by berkeman >>
    Last edited by a moderator: Jul 27, 2010
  7. Jul 27, 2010 #6


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    Staff: Mentor

    Please do not post links to articles about how to "hack" and create a real radar gun. As explained already in this thread, that requires approval by the FCC.
  8. Jul 27, 2010 #7


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    And as explained to you already in this thread and in your previous one on this subject:


    you may not transmit in the RF spectrum unless you do it according to the rules (which vary in different parts of the spectrum).

    It's great that you want to experiment with electronics and build things -- I definitely encourage you to do that. But you need to understand and acknowledge that you can't just experiment with building RF transmitters, with little knowledge and no license.

    What exactly are you trying to do with this 10m car motion detector? You can probably use ultrasound as the detection methodology, and then all you have to worry about is ear safety.
  9. Jul 27, 2010 #8
    I am sorry for posting the link - I guess I thought that a toy that was manufactured would meet all FCC standards. I didn't bother to read the whole page. I will refrain in the future.
  10. Jul 27, 2010 #9
    The FCC!?!

    Simple question: is it only forbidden to link directions for hobby projects that aren't legal in "the land of the free*"? If legislation differs amongst USA states, which state is PF policy determined by? Obviously not every PF user is legally prevented from building and using radar speed meters in appropriate circumstances.

    *especially speech :wink:
  11. Jul 28, 2010 #10
    If an illegal act, process or device is posted with the consent of the forum then what ever laws governing the the owners of the forum apply. They can be held criminally and or civily liable for what goes on here. I understand that freedom of speech ends where the rights of others are violated by it. We are guests here and we agree to follow the rules set forth. There are lots of other places that we can go if we don't like the rules here. I think of it as being in a neighbors house; if you don't like his rules then you are free to go home. I made a mistake - I could be banned for it - I got a warning and I learned not to post information like a direct link. I will be more dilligent.
  12. Jul 28, 2010 #11


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    Yeah, FCC I'm pretty sure. That's the national US federal body that governs the radio spectrum here. The radio spectrum is considered a shared national resource, so that's why there are laws about how it can be used, including licensing various parts of the spectrum (and ensuring that transmitters in areas of the spectrum do not interfere with other areas).

    It's not a free speech issue. It's a "don't mess up the shared resource" issue.

    And there are plenty of folks who build hobby transmitters and use them (see my callsign below). We just know the FCC rules, build and test our equipment to comply, and have the appropriate license to be transmitting in the appropriate bands. When you get newbie folks who don't know what they are doing, and aren't aware of the laws and why they exist (to prevent harmful interference), that's when there are problems.
    Last edited: Jul 28, 2010
  13. Jul 28, 2010 #12


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    Staff: Mentor

    It was just a PM, not a warning. :wink:
    Last edited: Jul 28, 2010
  14. Aug 1, 2010 #13


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    Sinced drakecia wants to detect a car at 10 meters, measure the distance and speed, then transmit that to a central computer, why insist on using RADAR?

    SONAR would probably work quite well. See Poloroid acoustic rangefinder project kits, or similar units to measure distance. Then you can use RF or infared to transmit that distance to your computer. There, you can calculate velocity.
    Last edited: Aug 1, 2010
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