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loss of range

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  • loss of range


    I’m pretty new to supplying data to FR24. Been using an SBS-1er box with external aerial for over ten years with great success and get a range of 200 miles in certain directions. Decided to try my hand with a raspberry pi a couple of months back with the intention of supplying data to FR24 which I use on the go. Wanted to go to the pi so I could leave it on 24/7 and not have a pc running 24/7. Set the pi up no issues at all added FR24, again no issues connected the FlightAware stick to my external aerial and bingo it worked. Again picked aircraft up 200 miles away no issues. Over a two month period supplied my data and on average picked planes within a 200 mile range every day.
    Now to my problem, decided to have a clean up in my man cave on Sunday and had to disconnect the aerial from my pi and stick. After I reconnected it, I was only picking aircraft up with a max range of 50 miles and I don’t pick up aircraft directly over me at height. I’ve checked everything, all the connections switched the pi off and on. I reconnected the sbs-1er box to the external aerial and I can still see planes 200 miles away. I re-formatted my sd card re-installed noobs and re-installed FR24 still only seeing planes within 50 miles and not overhead. I my ranges and aircraft view with the dump1090 web page
    Can anyone suggest how I get my range back please.



  • #2
    Does your antenna (aerial) have a TMA (tower mounted amplifier) RF amplifier at the antenna? Did you perhaps install the DC power injector at the radio end backwards? If you did that, you would be supplying DC power to the FlightAware stick instead of the TMA. Please note that the ProStick (orange case) and the ProStick Plus (blue case) both have RF amplifiers inside, making adding a TMA a marginal proposition for anything more than compensating for coaxial cable losses.

    Another possibility is something fell apart inside the FlightAware stick. I have a ProsStick Plus running PiAware.
    When it first arrived, there was an intermittent connection on the PCB. Bending the PCB at the SMA connector would cause dramatic changes in receive sensitivity. It took me about an hour under the microscope to find a bad solder connection. It's been fine since then. You might try a different dongle if you suspect a problem with your existing one.

    Also, for troubleshooting receive problems, I suggest that you login to the RPi with SSH. I use Putty on Windoze. At the shell prompt, run:
    $ view1090-mutability
    You should see a few lines of decoded ADS-B text. Look at the RSSI (receive signal strength indicator) column. Wiggle antenna cables and connectors. Look for drastic changes in signal level.
    If screen clutter is a problem, view1090-mutability has some options to filter the output and reduce the number of lines to one, making it easier see level changes.
    $ man view1090-mutability

    Yet another possibility. The inclusion of an RF amplifier in the FlightAware ProStick can cause overload problems if you're using a high gain antenna (> 8dBi) and/or are in an area infested with 1030 MHz interference from military and ACAS systems.
    The dynamic range of the R820T2 tuner is limited. Increasing the front end gain and raising the noise floor will make the dynamic range even smaller. FlightAware recommends reducing the gain setting:
    I've only had to do this once, on a mountain top that was crowded with all manner of RF sources. None of the receivers I tried could hear anything, even with various 1090 bandpass filters installed.

    Someone will probably ask how to lower the gain in FR24. I thought I knew, but it didn't work. 49.6 dB is the maximum gain.
    $ cat /var/log/dump1090-mutability.log
    Sun Oct 11 23:01:49 2020 BST EB_SOURCE EB_VERSION starting up.
    Using sample converter: UC8, integer/table path
    Found 1 device(s):
    0: Realtek, RTL2832U, SN: 00001000 (currently selected)
    Found Rafael Micro R820T tuner
    Max available gain is: 49.60 dB
    Setting gain to: 49.60 dB
    Gain reported by device: 49.60 dB
    Allocating 15 zero-copy buffers
    This was run with a genuine FlightAware ProStick (blue). However, my attempts to tweak the /etc/fr24feed.ini with various process arguments failed. Anyone have a answer or a hint?
    Last edited by Jeff Liebermann; 2020-10-11, 22:23.


    • #3
      Hi Jeff

      A big thank you for responding to my plea for assistance.

      Going over the points you have put forward. My external antenna does not have an ampler connected to it.

      Secondly my RSSI numbers are normally in the range 28-35 occasionally i get something in the teens but these pick ups are normally low altitude out of my local airport which is 6 miles from me Manchester (UK).

      The gain on the antenna is quoted at 9dBi so just outside the number you advised.

      As to gain i have mine set at 49.6 in dump1090 my FR24feed.ini file does not have a gain guide stated.

      I am worried that one of the pieces of my kit is faulty so today i have ordered a new FlightAware stick and a new raspberry pi power supply, i was already running a Raspberry pi power supply. I will see if these make any difference when they arrive. The current stick does get very hot the SMA connector is to hot to touch without a cloth over my finger when its running. I believe this may be normal.

      Thanks again for the advice/input.



      • #4
        Having graphs helps judge performance, but i'd recommend to install a stand-alone decoder before doing that:

        Running either of the decoder install script and then running the install script for the graphs is all you should need to do.
        Note setting gain and the local map will change a bit.


        • #5
          I did install your ADS-B receiver and then the graphs the graphs have been a major help.

          This morning a new power supply and FlightAware dongle arrived. First fitted the new pi power supply, no change, then fitted the new FlightAware dongle and I'm now back to where i was two weeks ago. my range has gone from 60 mile max to 200 mile with a big increase in number of planes picked up.

          While i'm glad I've fixed the problem the dongle must be very temperamental as my first is less than three months old.

          Thanks again to Jeff and wiedehopf for their input.



          • #6
            They usually hold up better, are you in a very hot environment?

            If you don't need the entire setup to be contained in a box, a cheap fan running on 5V from the RPi will reduce temperatures significantly and be whisper quiet:

            You can also pop open the clips and remove the molded plastic halves around the FA Pro+ stick.
            Not running a plastic case on the RPi will also help as it retains the heat and funnels it into the stick via the USB connection.

            Running the rtl-sdr v3 + rtl-sdr 1090 LNA is a good (usually better performing) alternative to the FA Pro+ if you have more issues, it tends to run cooler as well as it radiates via the metal case.


            • #7
              Thanks again for the additional info and recommendations. Which i will be looking at I'm just so glad I've moved back to where i started i want to leave things alone for a while. As to the heat issue this stick is running much cooler than the previous one i can touch this one no problem. I've put a short extension cable between the pi and the stick and that also seems to have help both items my pi is running 5C lower than before.



              • #8
                Originally posted by wiedehopf View Post
                Running the rtl-sdr v3 + rtl-sdr 1090 LNA is a good (usually better performing) alternative to the FA Pro+ if you have more issues, it tends to run cooler as well as it radiates via the metal case.
                The RTL-SDR Triple-filtered LNA is very good.

                I dont use it with rtl-sdr v3 dongle or FA prostick+. Instead I use it with Generic DVB-T Bias-T with 5v dc adaptor. This attangement reduces dc load on Pi USB port / dongle. The amplification of LNA is sufficiently large, so abscence of an LNA in generic dongle does not result in any reduction in performance.

                Last edited by abcd567; 2020-10-13, 21:40.