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Thread: best antenna

  1. #101
    Captain abcd567's Avatar
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    Quote Originally Posted by 1090 MHz View Post
    Wow that's impressive, and encouraging, to see that with your home-brewed setup you're getting over 400 Km reception! I see you have a directional pattern to the South-East, suggesting you're in a tall building facing that same direction. What floor are you situated on may I ask ?
    You guessed right, my window faces South-East, ad I am located at 65 feet above ground level

  2. #102
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    Quote Originally Posted by 1090 MHz View Post
    Wow that's impressive, and encouraging, to see that with your home-brewed setup you're getting over 400 Km reception! I see you have a directional pattern to the South-East, suggesting you're in a tall building facing that same direction. What floor are you situated on may I ask ?
    Height of ADS-B Receiving Antenna does NOT appreciably affect the Range.

    In case of Ground-to-Ground Communications at UHF/Microwave, the heights of both the receiving and transmitting antennas greatly affect the range.

    In case of Air-to-Ground ADS-B Communications, the Transmitting antenna is on the Aeroplane, which is several thousand feet high. The contribution of height of receiving antenna to the overall range is therefore not appreciable.

    The range is combination of ranges of transmitting & Receiving antennas.
    Overall Range = Range of Transmitting Antenna + Range of Receiving Antenna
    = 1.41 x √h1 + 1.41 x √h2 miles
    ,
    where
    h1 = height of transmitting antenna in feet.
    h2 = height of receiving antenna in feet.

    Based on these formula, I have calculated the Range for various heights of Receiving Antenna and Airplane, and have tabulated the results. These results show that increasing height of RECEIVING Antenna from 25 to 200 feet does not appreciably affect the overall range of ADS-B.

    PLEASE SEE ATTACHED PICTURE for the tabulated results:
    ADS-B-Antenna-Height-&-Range.gif
    Last edited by abcd567; 2013-09-27 at 21:36.

  3. #103
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    ABCD, You come across as quite a clued up radio amateur, or someone who works with signals and propagation? Wish we had a direct line of comms tonight, was building a larger collinear and would have liked to tap your knowledge. Anyways, my DIY #2 will be up for testing tomorrow. Upgrading from an 8 to 14 element. Hoping for the best.

    This link also muchly shows what you are saying. http://www.heywhatsthat.com/main-090...?view=ML2O2PSQ Create new panorama, enter your coordinates, receiver height, let it plot... then on the map, select: Up in the air.
    With my little knowledge I had a month ago, that plot gave me a prediction as close as what I am getting at present. Can also set your AC min and max height, then it shows your reception based on that.
    Last edited by HermanZA; 2013-09-27 at 22:47.

  4. #104
    First officer 1090 MHz's Avatar
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    We always look at the antenna height based on 2 measurements, one being the Height Above Sea Level … (HASL) and the Height Above Average Terrain (HAAT)

    HASL is used as it’s a common reference point. HAAT is important in that the antenna is high enough to clear any obstacles in the way.

    I’m located at 620 feet Above Sea Level with a HAAT of 50 feet … overall height will be 670 feet HASL.

    Our Airport YYZ is at 545 feet HASL … giving my antenna, which is 16 Km away, an overall height of 125 feet over the airport. This should give me good ground coverage of the airport too.

    As for maximum distance, the earth is round, and no matter how high up a plane is it’ll eventually fall behind the horizon of the receiving antenna. But it looks like we can get up to 500 Km range from what I’ve seen. It’ll be interesting to see when my station goes live!
    Last edited by 1090 MHz; 2013-09-28 at 08:23.

  5. #105
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    Quote Originally Posted by 1090 MHz View Post
    We always look at the antenna height based on 2 measurements, one being the Height Above Sea Level … (HASL) and the Height Above Average Terrain (HAAT)..........
    Thanks for the technical information. Yes the limiting factor is curvature of earth, no matter how high is the plane or receiving antenna...practically observed limit is about 500 km. I am eagerly waiting to see your results when your station goes live.

  6. #106
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    Quote Originally Posted by HermanZA View Post
    ABCD, You come across as quite a clued up radio amateur, or someone who works with signals and propagation? .......
    Wow, the link you gave ( http://www.heywhatsthat.com/main-090...?view=ML2O2PSQ) is great.
    Thanks for sharing.

  7. #107
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    Quote Originally Posted by HermanZA View Post
    [snip]This link also muchly shows what you are saying. http://www.heywhatsthat.com/main-090...?view=ML2O2PSQ Create new panorama, enter your coordinates, receiver height, let it plot... then on the map, select: Up in the air.
    With my little knowledge I had a month ago, that plot gave me a prediction as close as what I am getting at present. Can also set your AC min and max height, then it shows your reception based on that.
    This is something Mike should look at to help decide when placing FR24 receivers.

    I have trees to the north of me at 50 feet - yet I still getting 200kms range there, and clear skies to the SE and only about 100km - the google KML plot from this site shows that my LOS to the SE to a 'remote height' of 25000 feet is about 1km and explains that once I get my antenna above the roof peaks it will even out the plot a little but my view to the SE will still be crap in comparison.

    The trees have less blocking effect than the in-perceptible surrounding low hills.

  8. #108
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    It would be interesting if some of you can use that link to plot your sites prediction and then also show your actual coverage. Think I'll start a new thread (a bit later today) and post mine, and hopefully others will do the same. It would be interesting to see the prediction vs real coverage. Might just help us lot in seeing where we can better our coverage by some means or another.

  9. #109
    First officer 1090 MHz's Avatar
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    Quote Originally Posted by abcd567 View Post
    Wow, the link you gave ( http://www.heywhatsthat.com/main-090...?view=ML2O2PSQ) is great.
    Thanks for sharing.
    Unfortunately it's designed for wireless ISP planning... which is point-to-point short range links. The program would not allow me to do anything over 100 miles. Has anyone figured a way around this limit?

    I did come across this program that is a plugin for Google Earth ... there is a small Pay Per Use user cost.... but it looks very promising. https://cloudrf.com/Keyhole_Radio
    Last edited by 1090 MHz; 2013-09-28 at 10:52.

  10. #110
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    Now what did I do wrong here? New antenna made up of 14 elements of LMR400 cable, feeding down with RG6. Velocity factor is the same for both cables, cable runs and antenna height are the same, yet the new antenna gives poorer coverage than the old. New one was tested for shorts and its clean. Also open ended (no resister).

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