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Estimating the receiving signal strength 2.4ghz

  1. Mar 26, 2012 #1
    Hello every1 .. i am sophomore so excuse me if i ask anything stupid/obviouse.

    so there are allot of proximity devices but with short range so i was thinking of making one with 2.4Ghz ℝℂ tx & rx. these typicaly have range to about 1km.

    So all i wanna know is if there is a way to connect the arduino or sumthing to the RECEIVER at any channel or at the antenna so i can measure the strength of the signal being received from the transmitter and hence estimate the distance from the transmitter. It doesn't have to be accurate.

    →→→THANXX gr8 forum!!
     
  2. jcsd
  3. Mar 26, 2012 #2

    davenn

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    Estimating distance to transmitter unfortunately isn't that easy
    The are just so many variables that come into play..... To name a few....
    Tx power
    Rx sensitivity
    Antenna gains at each end
    Are you getting a direct signal or a reflected signal or a mixture of both
    ( this last one would be the biggest killer to distance estimates over a relatively short distance)

    Now radar works very differently by working out the time delay of receiving the reflected pulse off some object. But for a relatively straightforward TX and RX system distance measurement would be extremely difficult.

    Now if you have the tx and rx sync'ed and timing done very accurately ...with the transmitter sending out pulses you would be able to time the delay in the arrival of the pulse from the transmitter. But over such a short distance, say less than a few kilometers and with the radio pulses traveling at the speed of light, the delay times are going to be absolutely tiny!! And could easily be masked by inaccuracies in your sync'ing system and general timing quality

    Dave
     
    Last edited: Mar 26, 2012
  4. Mar 26, 2012 #3

    sophiecentaur

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    RF propagation involves so many different variables that you can't hope to do better than just a 'rough estimate' of the distance travelled by a signal. (Cosmologists are stuck with this method for measuring the distances of really distant objects and they are grateful for ball-park figures).

    GPS is good and works on the principle of measuring the differences in arrival times of signals from a number of different satellites. Ancient (about 50 years ago, I think) systems likeDecca did the same sort of thing by having a number of base stations, synchronised to each other. The receiver compared the relative phases of signals received from each station and could place itself on a grid of hyperbolic lines, on a chart.

    Though, actually, you are talking in terms of a couple of km separation so why not use smart phones, GPS and a navigation app to tell where the two terminals are and communicate that info by 3G? All the tek is there for you (you probably have it in your pocket right now) and you can tweet your friends at the same time.
     
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