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Feeder hardware in urban area

Discussion in 'Hardware' started by Tex-Twil, May 5, 2019.

  1. Tex-Twil

    Tex-Twil New Member

    Hi,
    I'm thinking about setting up a feeder. I do already have a rPI. For the ADSB receiver, it looks like the FlightAware Pro Stick Plus is the way to go but I wonder what signal I would get given that I live in central Berlin (Germany). My flat is on a 3rd floor of a 5 floor building and I do have a balcony.

    Thanks for your tips

    cheers
     
  2. Ads-b radio signals propagation work pretty much on a line-of-sight model, so what you will get depends very much on how much open sky you can view from your balcony,
    even if there is lot of traffic above your head.
    Pro Stick Plus is the right choice, the integrated filter will help you to get rid of noise and strong cellphone tower interferences.
     
  3. Tex-Twil

    Tex-Twil New Member

    ok thanks!
     
    Jhonny Monclair likes this.
  4. James

    James Administrator Staff Member

    I agree. Good advice.
     
    Jhonny Monclair likes this.
  5. paulCIA

    paulCIA New Member

    I had the curious situation of living in a ground floor apartment in Manhattan with about 3% of the sky visible. So some of the busiest airspace anywhere with pretty much the worst possible RF conditions. It kinda averaged out to a decent but certainly not particularly great or terrible setup. Range was limited to 30nmi but within those 30 mi I did pick up almost all aircraft going in or out of LGA but only one way in or out of EWR and JFK. A low-noise amplifier in the RX chain did help but not as much as you might think, problem was definitely not the strength of any signals it was all the RF and multipath interference and if I turned up the amplification too much it just killed everything by overloading the RTL. Actually I'm pretty sure most of the signals I was receiving were being reflected off the buildings across the street because MLAT worked noticeably better when I set my position to across the street and increased the elevation setting by about 20m, which is where my phone told me I was when I used GPS-only positioning, it's a lot like trying to use GPS indoors, it still works just not very well, makes sense since they're on similar frequencies.

    So lets just say you should have a much easier time than I did if you actually can see any sky. 5 miles from the empire state building where most TV and radio transmitters for the city are located. the FM radio signals were so strong and the quantization error of an RTL-SDR so poor I could listen to the aliases of any very strong FM stations at 2nd, 3rd, and 4th harmonics of their center frequency.. So yeah basically the SNR was guaranteed to be shitty no matter what and by far the most important thing is a good 1090 MHz notch filter, even better if it's builtin to the receiver with an amplifier.

    From what I've seen having them as three separate devices, unless you're running a very long feeder line it doesn't really matter if the filter and amplifier are on the receiver or antenna end of the line, and replacing the three with a $10 RadarBox FlightStick made everything work much better than anything I was able to get out of any different configuration of a separate filter and LNA or antenna or feedline. I was just using a simple vertically oriented dipole antenna, that worked a lot better than anything I was able to get out of whip ground planes, makes sense if the signals really are coming from across the street rather than straight up in the sky; the straight up null in a vertically oriented dipole doesn't much matter if you're not receiving any EMF from straight up anyway; but the latter might work better with more straight-up sky view like from your balcony, but it also depends on air traffic patterns; if nobody's flying overhead a ground plane might not help you with a perfect sky view. The aircraft themselves do after all use vertically oriented dipoles to transmit the signals, since ATC isn't generally located directly underneath the aircraft.
     
    Last edited: May 17, 2019 at 9:13 PM
  6. wiedehopf

    wiedehopf New Member

    You probably want the dark blue FA filter to go with the FA prostick plus.
    The prostick plus LNA is rather easily overloaded by LTE ground stations it seems.

    As the total cost then goes up quite a bit, you might as well buy the combination of an rtl-sdr blog v3 dongle and the RTL-SDR BLOG 1090 MHZ ADS-B LNA
    (can't post links yet it seems)

    It's much better in high noise environments.
    Be sure to get the filtered ADS-B LNA, not the unfiltered one.