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Thread: How to get the signal from an external antenna placed in a tower down to the ground?

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  1. #1
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    Question How to get the signal from an external antenna placed in a tower down to the ground?

    I may have access to a very high tower here at our research station in Cotonou to place an antenna and receiver. I have read something on the receivers/antenna's that are placed high in communication/telephone towers and that give an excellent coverage. Can't find the article back though.

    Suppose I could place an antenna in a tower, then how to get the signal down to the receiver? I assume the Radarcape receiver is not placed next to the antenna? Doees it need additional equipment?

    thanks for your time!

  2. #2
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    Long, high quality down lead - but I think people would like pictures of the tower from a distance (possibly someone or something next to it to give scale) and a picture of the present equipment that is already on the tower.

    People who have receivers near cellphone towers do have problems - maybe someone could recommend filters, anything else required, etc. too

  3. #3
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    ok, the tower is lcoated at 6.421N, 2.327E and IF I manage to get an antenna up and a receiver down then it could provide ground coverage of the airports of Cotonou (about 10km), Lagos (110km) and Lome (120km) and I guess near-ground coverage for Accra (300 km). I saw that that the receiver based in Dakar, Senegal gives coverage on the ground for Nouakchott which is a distance of approx. 400 km over sea.

    The tower here is quite high and (unfortunately) it appears to have cellphone facilities.

    20140603_165233.jpg20140603_165356.jpg20140603_165408.jpg

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    Quote Originally Posted by Xanderix View Post
    ok, the tower is lcoated at 6.421N, 2.327E and IF I manage to get an antenna up and a receiver down then it could provide ground coverage of the airports of Cotonou (about 10km), Lagos (110km) and Lome (120km) and I guess near-ground coverage for Accra (300 km). I saw that that the receiver based in Dakar, Senegal gives coverage on the ground for Nouakchott which is a distance of approx. 400 km over sea.

    The tower here is quite high and (unfortunately) it appears to have cellphone facilities.

    20140603_165233.jpg20140603_165356.jpg20140603_165408.jpg
    Hi!
    What i can see, you will need a filter to get full ADS-B signal. I tell it after the experience to install 4 receivers at high towers like yours. We have installed it not at the tower but in a small mast next to them on the roof of the typical "house" where all equipments are inside. We only needed 5 meters cable in each by luck.
    Ah! and thanks for adding your "radar" in my map! ;-)
    Covering the Canary Islands, Madeira & North West Africa
    F-GCRR1: 565 meters high. F-GCRR2: 614 meters high. F-GCRR3: 604 meters high.
    F-GCRR5: next to the airport. Improving Canary Islands and Western Sahara MLAT.
    F-GCRR6 (Ex-FGCRR4): 358 meters high. F-GCRR7 : 300 meters high.

    Rafa - Lanzarote, Canary Islands, NW Africa - EA8APP

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    The db loss due to height might kill the height advantage though unless you have an LNA to fix the issue. Do what the cell carriers do and put the radios up top on the tower.

  6. #6
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    Are you talking about placing your antenna / dongle based equipment on the tower or going for something altogether smarter like an FR24 receiver?

    I'm sorry this appears to be off topic

    I am using a Raspberry Pi + dongle based receiver that is proving very reliable, normally not needing any attention - write up is post 8 on this thread http://forum.flightradar24.com/threa...e-to-feed-FR24

    I have added a cheap amplifier between the antenna and the downlead - this has increased range by maybe 10% - more is unlikely since I'm receiving at the distance (about 400km) where the planes at 40000 feet go over the horizon.

    The reason for mentioning this is that if you were thinking of putting a receiver into a box on the antenna - this would be practical, but being close to the equator special consideration would have to be given to prevent overheating both due to heat from the dongle + Pi as well as heat from the sun.

    A tall mast is advantageous, but is not essential if another tall location can be found with clear line of sight all around, that might do nearly as well.

    You can check what might be 'seen' by going to http://www.heywhatsthat.com/ - putting in the antenna location and hight - then when the map is displayed, click 'Up In The Air' and putting in 30000 and 40000 feet ... then zoom out

  7. #7
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    The towers height would be an absolute advantage, as height is everything in terms of getting good coverage on ADSB. However, mounting it on the mast, you would like to have a stand-off from the tower structure (as large as possible from the body of the tower), to minimise any "shadow effect" from the mast.
    Going as high as possible might not be such a good plan in the beginning, as you will most likely play around and improve the setup (or run into problems that you need to solve), so maybe a nice height like say 15m off ground will be good for starting the setup (or enough to clear over trees and buildings). Once you have sorted everything out and have it the way you like, go for gold and go as high as what you can go.

    As Peter said, looking as a Pi might be a good solution, but bear in mind the heat in your country - I had terrible problems with mine in the summer. When I was in Cameroun a few years ago, the summer heat in February was terrible, and I doubt the Pi would survive that, unless you give it proper airflow or keep it in a transmitter room, or similar.
    Also keep in mind the lightning factor - not sure how bad it is in your part, but it seems the Pi is rather sensitive to lightning strikes in its near vicinity.

    The more distance you have between the antenna and the receiver (RTL stick or a built device), the more cable loss you get, so the better cable you need to use, or add an inline amplifier. But, which ever way you go, us lot on the forum will be able to help and assist and share our experiences. A lot of us are using normal satellite cable (RG-6) and make up for the loss with an inline amplifier. Some folks who have access to better cable, dont need to amplify what they loose over the distance. Its a matter of cost vs. available cable vs. what you willing to spend.

    BTW: I see T-DBBB3 online at present ... is that you ?

  8. #8
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    Herman, Thanks for your suggestions. I indeed see the limitations there are with height and, indeed, the climate. Even my laptop gets sometimes overheated despite sufficient airconditioning... We had a lightning strike some time ago that killed some 30 computers... Temperature is year round 30 degrees and humidity is high. Pi is not an option based on your experience. I need something that needs little maintenance.

    The good part is that we have 24/7 power and internet. Internet speed is a sizzling 6 Mb/s! One of the fastest connections in entire W-Africa. An antenna up the tower would definitely give ground coverage in three (relatively) busy airports here (Cotonou, Lome and Lagos), but will technically become too challenging for me.

    T-DBBB3 is my receiver here in the office. It's just the small antenna only inside, so practically no coverage. Normally I have T-DBBB1 running (I guess we have a power cut at home right now) with a roof top antenna. Coverage is up to 400 km over sea, but there is a large hotel next to me which prevent signal to be picked up that is west of Cotonou towards Lome.

    Thanks again.
    Last edited by Xanderix; 2014-06-04 at 14:33.

  9. #9
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    Quote Originally Posted by Xanderix View Post
    Herman, Thanks for your suggestions. I indeed see the limitations there are with height and, indeed, the climate. Even my laptop gets sometimes overheated despite sufficient airconditioning... We had a lightning strike some time ago that killed some 30 computers... Temperature is year round 30 degrees and humidity is high. Pi is not an option based on your experience. I need something that needs little maintenance.

    The good part is that we have 24/7 power and internet. Internet speed is a sizzling 6 Mb/s! One of the fastest connections in entire W-Africa. An antenna up the tower would definitely give ground coverage in three (relatively) busy airports here (Cotonou, Lome and Lagos), but will technically become too challenging for me.

    T-DBBB3 is my receiver here in the office. It's just the small antenna only inside, so practically no coverage. Normally I have T-DBBB1 running (I guess we have a power cut at home right now) with a roof top antenna. Coverage is up to 400 km over sea, but there is a large hotel next to me which prevent signal to be picked up that is west of Cotonou towards Lome.

    Thanks again.
    I'd suggest trying the Pi, it does have the advantage of being low cost, simple, starts with the power being applied and is remotely manageable.

    Take care with grounding the antenna adequately so induced high voltage spikes don't reach the equipment that should protect from nearby storms - but you'll never protect it from a direct strike

    Take care to ensure it doesn't overheat, I do appreciate the difficulty here, If the equipment can be put somewhere cool it would be excellent - but if it has to go outside in a box, think about what can be done to keep the sun off the box and what can be done to cool the inside. I think that would be a great project for someone to work out how to do in a hot country. (maybe using a 'peltier cooler' - this is a low cost electrically powered tile that pumps heat from one side to the other, connect the one side to a 'cooling heat sink' inside the box, the other to a 'hot' heat sink outside the box to take the heat away, A peltier cooler is what is used in those cool boxes you can plug into the car cigarette lighter)

    It's a pity you couldn't put a receiver on the hotel with a Wifi connection back to the office.

    It would be good to see if you can receive any ADS-B signals next to those cellphone antennas.
    Last edited by peterhr; 2014-06-04 at 17:35.

  10. #10
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    Height makes little difference for ADS-B since it is ground-to-air (other than clearing obstructions).
    You can see the detailed discussion and the table illustrating the relationship between antenna height and range here:
    http://forum.flightradar24.com/threa...antenna/page11
    As you can see, when aircraft altitude = 1000 ft, antenna height = 200 ft, the range is only 100 km.
    That means probably you won't be able to cover those >100km airports.

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