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Triangulate a signal

Discussion in 'Electronic Basics' started by Anders Nesheim Vinje, May 13, 2005.

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  1. I guess this is not really a electronics question but some of you guys may
    know this anyway.

    I was wondering how to triangulate a radio signal.
    I understand that you would need three recivers at least. But how do you
    measure it and get the exact position? Do you check the diffrence in time at
    each reciver since it takes some time for the radio signal to travel?

    Anders N.Vinje
     
  2. John Fields

    John Fields Guest

    ---
    You really only need two receivers. The receivers have directional
    antennas connected to them, and the antennas are pointed at the target
    so that the input signal to the receiver is maximized. Then, when
    that's done, if you draw a line from each antenna in the dirction in
    which it's pointing, where the lines intersect is where the target is.
     
  3. Blake

    Blake Guest

    Actually, because nulls in the antenna pattern are much sharper than the
    lobes, you usually adjust the antenna for minimum signal. But the principal
    is the same.
     
  4. John Fields

    John Fields Guest

     
  5. Bob Eldred

    Bob Eldred Guest

    What are you trying to do? The above posters mentioned signal strength
    methods to determine direction to a source. This works, sort of, it's a 20th
    century method. If there is modulation on the RF carriers that can be
    precicely timed, accuracy can be much greater than the direction finder
    method.

    Imagine two receivers, or three or even four, each with a very accurate
    clock. Now imagine that there is a detectable event in the modulation like
    the start of a frequency or note pattern that is detected at each receiver.
    Each receiver notes the precise local arrival time of the event and from
    that calculates the difference in distance to the source between it and the
    other receivers. From these distances, circles of distance from each
    receiver can be plotted. A vector or direction from each receiver can be
    calculated from the circles and these vectors, in turn, intersect where the
    transmitter is located. This can be very accurate depending on the time
    resolution. Ten nanoseconds of time resolution will give an accuracy of 3
    meters in location.

    This is the way GPS works only there is one receiver and several satellite
    transmitters but the priciple is the same. The precise timing and event
    marking are in the coding of the transmitter modulation patterns and a
    microprocessor does all of the required calculations and generates a
    display.

    A crude system working on these princilpes could work on any radio signal.
    The receivers would need some electronics to establish the time base and to
    detect radio modulation events. A simple readout could display the local
    event time and one could manually plot the circles and vectors on a map to
    determine location from these readouts. I suppose this is way beyond what
    you want to do.
    Bob
     
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