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Thread: Which is more important: Hardware, sightlines or elevation?

  1. #1
    Flight attendant
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    Which is more important: Hardware, sightlines or elevation?

    Hi.

    My stock-standard FR24 ADS-B rig is at ~1,830m ASL on a mountain range (-44.414, 170.01) and I'm detecting and losing aircraft at ranges between 500-600 km.

    I'll soon be moving the setup to the highest peak, ~1,900m ASL: Not only is it 70m higher than the current site, it has unobstructed 360 degree horizon views down to 0-1 degrees alt., unlike the current site, which loses up to 6 degrees alt. in a couple of directions.

    There is essentially zero noise at this site -- I'm the only thing up here, and there's 2/3rds of nothing in most directions for scores of kms -- so is any hardware change likely to further increase the range?

    Cheers, BPO.
    Last edited by BPO; 2014-03-22 at 03:22.

  2. #2
    Captain
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    It will be interesting to see if FR24 remove the 400km limit from your stations submissions that they have in place for others - this was put in to limit false data that was causing flights to jump around all over the planet.

  3. #3
    Team FR24 Mike's Avatar
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    Most important is line of sight. But of course hardware is important as well and elevation will increase line of sight.

  4. #4
    Captain
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    Height is king for ads-b receiving.

    But there will be a limit to how far your can see. Normally around 250-300nm is the standard quote for range, and also the effect of curvature of the Earth has its effect. But standard doesn't apply to your case as your are going to be 1900ft ASL. I am not sure who has the highest FR24 antenna but yours probably will be on top of the list. There is a software to calculate range around the best antenna thread which is buried somewhere and I couldn't locate it just yet. I will have a dig. We will know the range once your set up goes online at the peak.

    Here is a quote by abcd567 about range: http://forum.flightradar24.com/threa...ll=1#post43772

    Oh Mike also posted too... Different people different opinion haha.
    Last edited by North Borneo Radar; 2014-03-22 at 07:29. Reason: grammar, typo

  5. #5
    Flight attendant
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    Right, so the consensus does seem to be pointing toward line-of-sight.

    BTW, if you're wondering whether I plucked those range figures out of thin air, I determined them by 'print screen'ing the data as it changed on several flights until they disappeared, then using the coordinates and Google Earth's ruler tool to measure the distance between the receiver and the last positions of the aircraft.

    The longest range via this method was 551 km, but I don't really know how accurate that can be.

  6. #6
    Team FR24 Mike's Avatar
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    Height is not so important. Increasing antenna elevation from 1000 to 2000 feet will increase your range only by about 2-4%. So it's all about sight.
    But of course sight often comes together with elevation.

  7. #7
    Captain
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    Quote Originally Posted by North Borneo Radar View Post
    Height is king for ads-b receiving.

    But there will be a limit to how far your can see. Normally around 250-300nm is the standard quote for range, and also the effect of curvature of the Earth has its effect. But standard doesn't apply to your case as your are going to be 1900ft ASL. I am not sure who has the highest FR24 antenna but yours probably will be on top of the list. There is a software to calculate range around the best antenna thread which is buried somewhere and I couldn't locate it just yet. I will have a dig. We will know the range once your set up goes online at the peak.

    Here is a quote by abcd567 about range: http://forum.flightradar24.com/threa...ll=1#post43772

    Oh Mike also posted too... Different people different opinion haha.
    1900 meters - not feet ...

  8. #8
    Captain
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    Quote Originally Posted by peterhr View Post
    1900 meters - not feet ...
    My bad thanks for correcting typed in a hurry when having a short break at work.

  9. #9
    First officer
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    Just make sure you have good quality coax cable, so your not imposing unwanted losses is about all i have to add.
    T-EGLF8

  10. #10
    Purser
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    Quote Originally Posted by BPO View Post
    Which is more important: Hardware, sightlines or elevation?
    The answer is "yes". Everything matters.

    • While people have seen good results using inexpensive DVB-T dongles and the inexpensive, untuned antennas included with them, using purpose-built gear will pull in more signal.
    • Since ~1GHz frequencies are all line-of-sight, putting your antenna where it can "see" more planes is vital. No antenna, feed line or radio can see through a mountain.
    • Elevation can help improve sight lines by putting the antenna above obstructions.

    Putting your antenna at the top of a mountain will not help much in receiving planes at cruising altitudes. But it can give you line-of-sight view of nearby airports, low level traffic patterns around those airports and TIS-B transmitters. Where I live (US), many commercial aircraft use UAT in place of ADS-B. UAT uses a different frequency and modulation, and there are very few hobbyist receivers for UAT. But because the FAA relays UAT broadcasts (using TIS-B) using a frequency and format that I can receive, many planes can be identified this way. I wouldn't be able to get those TIS-B transmissions if I wasn't at a higher elevation that gives me line-of-sight to the airport across town where the TIS-B facility is.

    In your case, the ability to track flights all the way to/from their originating airports will give you a better picture of each flight.

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