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Thread: Signal Triangulation Strategy #2

  1. #1 Signal Triangulation Strategy #2 
    Time Lord
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    Use two parabolic dish receivers.

    1) - Place the two receivers a distance apart from each other.

    2) - Continually adjust each receiver until the signal is the strongest.

    3) - Measure the angle that each receiver is facing relative to an imaginary line drawn between the two receivers.

    Based on those angles, and a knowledge of the GPS location of the two receivers, you should be able to use triangulation to calculate the exact location of the signal's sender. (Unless you don't have direct line of sight, like if it's being reflected off a mountain or something. )

    So basically.... any pair of humvees that overhears enemy chatter should be able to determine the exact locations of the chatter-ers.


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  3. #2 Re: Signal Triangulation Strategy #2 
    Forum Professor Wild Cobra's Avatar
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    Quote Originally Posted by kojax
    Use two parabolic dish receivers.

    1) - Place the two receivers a distance apart from each other.

    2) - Continually adjust each receiver until the signal is the strongest.

    3) - Measure the angle that each receiver is facing relative to an imaginary line drawn between the two receivers.

    Based on those angles, and a knowledge of the GPS location of the two receivers, you should be able to use triangulation to calculate the exact location of the signal's sender. (Unless you don't have direct line of sight, like if it's being reflected off a mountain or something. )

    So basically.... any pair of humvees that overhears enemy chatter should be able to determine the exact locations of the chatter-ers.
    Unless you accidentally aim with one of the side-lobes. Now are you speaking of GHZ range frequencies? A width of a parabolic needs to several times bigger than the wavelength. That limits you to UHF and SHF communications. Even then, the 3dB points of a parabolic are usually at least 2 degrees or more, unless it has a gain greater than 40 dB. How big is the parabolic going to have to be for the frequencies you are looking for? Is it even close to being portable?

    When I was a microwave communications technician, a common size antenna we used was a 6 ft. parabolic. It has a 40 dB gain for the 8 ghz band. Correct me if I'm wrong, but you are looking for VHF communications. not SHF. If you are talking of around 200 mhz, a 6 ft parabolic will only give about a 8 dB gain and not be so directional. To bring it up to a respectable 28 db gain and direction finding, the parabolic would have to be about 60 ft diameter for 200 mhz.

    Parabolics work best for SHF and higher frequencies.

    Example: Radiation pattern for antennas on 3.5 GHz:



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  4. #3  
    Time Lord
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    Hmmm. That pretty much rules this strategy out. I'm pretty sure that most insurgents use radios down in the Khz range.
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  5. #4  
    Forum Professor Wild Cobra's Avatar
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    Quote Originally Posted by kojax
    Hmmm. That pretty much rules this strategy out. I'm pretty sure that most insurgents use radios down in the Khz range.
    Your best bet for such frequencies might be three locations tied to a common computer. Each receiver would be timed via GPS and have a DSP programmed to evaluate the waveform of suspect transmissions. They each send their signal to a common computer that then triangulates using a differential approach. It takes three sites to give you a map grid, and a fourth to give you height. This is how cell towers locate emergency cell calls on the GSM network, but they don't have GPS and don't need it because of the higher frequency.

    That said, I still think it's a problem. With circuitry that can detect nanosecond difference in signal arrival, you still have ghost signals off the terrain to mess things up.

    wiki: Time Difference of Arrival
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  6. #5  
    Forum Professor Wild Cobra's Avatar
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    Normal triangulation is probably the best method to use.

    Maybe a multiple wind loop antenna can be tuned to the frequencies used, and normal triangulation used. Hard to say, it get's outside of my expertise.

    Maybe a magnetic loop antenna.

    Loop antennas are directional.
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