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Thread: Raspberry PI Dual tuners

  1. #11
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    geographical range of visibility

    Quote Originally Posted by Sam26K View Post
    ... I thought that's why all the signals drop off to black and software estimates take over when the planes are a few 100 miles out to sea....
    Since ADS-B radiation behaves like light, it is a matter of "geographical range of visibility", mainly due to earth curvature.
    https://books.google.de/books?id=xRq...bility&f=false
    with geographical range = 1.144 * (squareroot(object height) + squareroot(observers or antenna height)) with range in nautical miles and heights in feet, you get
    1.144 *( sqr(300)+sqr(30000)) = 218nm
    When mounting your antenna in a decent uphill position.

  2. #12
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    Quote Originally Posted by Sam26K View Post
    ... I thought that's why all the signals drop off to black and software estimates take over when the planes are a few 100 miles out to sea....
    Since ADS-B radiation behaves like light, it is a matter of "geographical range of visibility", mainly due to earth curvature.
    https://books.google.de/books?id=xRq...bility&f=false
    with geographical range = 1.144 * (squareroot(object height) + squareroot(observers or antenna height)) with range in nautical miles and heights in feet, you get
    1.144 *( sqr(300)+sqr(30000)) = 218nm
    When mounting your antenna in a decent uphill position.

  3. #13
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    You are right that 1Ghz is mostly line of sight but it does get diffracted through the atmosphere and the weaker signals can be picked up by higher gain antennas. But your general point of line of sight to less than 250 miles sounds right with most reasonable heights of an antenna.

    It would be nice if someone could talk someone into feeding FR24 from an ADS-B dongle from the ISS space station .

    BTW my antenna's altitude is about 60 feet above sea level right now and I receive up to around 180 nm but only directly out to sea or in directions with no geographical obstacles. The hills to the east limit it to about 60 miles. Omnidirectional co-linear with 6dB gain at 1095 Mhz from FlightAware.
    Last edited by Sam26K; 2016-01-21 at 11:24.

  4. #14
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    Back to rangler's question. How to use more than one dongle on just one Pi. Any idea?

  5. #15
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    Read post number 2

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