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Hi, Possible Interference

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  • Hi, Possible Interference

    Hi, I followed a link via the main page relating to problems with submitting data and statistics. I am in London and normally see around 1600 planes a day and avg 540/50 nm, currently I am seeing 300 at 3nm. I was advised to reset all of the connections and PSU etc, this was already done prior to posting so it wasn't connection related. I had already disabled IP6 so that wasn't part of my problem. In the end, member abcd567 suggested I ran some tests to check for interference.
    I ran the test and have the following snippets. The question is, am I suffering Interference and if so, whats the best filter to use? Also, whilst I am at it, are there better/worse DVB-T sticks out there as I just bought a generic one via ebay.



    I have just ordered a FlightAware Pro Stick Plus (USB SDR ADS-B Receiver) which I guess should be more suited to my needs?
    Last edited by markylondon; 2018-06-20, 15:53.

  • #2
    The generic DVB-T perform good. I have it for 3 years, and it works ok.

    In addition I use a combination of following:



    Please also have a look here:


    • #3
      thanks abcd567, I have already bought two generic DVB-T so now decided to just get something better. I do know I have two Mobile Radio masts nearby, one is maybe just 100meters from my house, the other 3 to 400. My scan looks like the conversion from csv failed half way, but do you think it shows bad interference?
      Last edited by markylondon; 2018-06-20, 09:25.


      • #4
        (1) Your scan does show interference, low at GSM800 mhz, and high at E-GSM900 mhz. As you mentioned proximity with Mobile Tower, a filter is very likely to improve reception

        (2) You have now ordered Pro Stick Plus (Dark Blue). It has a built-in SAW filter, and theoritically should not need any external filter. However in some locations, it is found insufficient and after adding an external filter, reception improved. This happened with me also.

        (3) In some locations with very strong signal at 900~950 mhz, the SAW filter of ProStick Plus, or even adding an external Flightawsre filter does not fully remove the interference. In such cases a better (and costlier) filter like Cavity Filter may be needed.

        The only way to find which filter will work for a particular installation is trial and error. You have started with "no filter", and now will try "integral SAW filter" of PS+. If this does not solve, add an external FA filter. In worst case you may have to use Cavity Filter.


        • #5
          Thanks, I will report back once I get the new SDR, will also try and do the network scan again to see if its any different.


          • #6
            Can you post the portion of scan between 820 MHz and 920 MHz? It is missing in your first post. The 820 to 900 MHz is Mobile Phone band GSM850

            Others who read this thread, will be at loss as they dont know how you got those scans.
            Here is the link to the thread describing how to get the scan. This may benefit many.

            Do I need a Filter? - Find RF Signals In Area



            • #7
              Here they are, not a lot there, maybe 850 isnt that popular in the UK? Just had a look, these are unused in the UK so thats why I have no data in that portion.
              Last edited by markylondon; 2018-06-20, 15:48.


              • #8
                GSM850 and GSM1900 are used in most of North, South and Central America (ITU-Region 2)

                E-GSM900 and GSM1800 are used in most parts of the world: Africa, Europe, Middle East, Asia (ITU-Regions 1 and 3)


                • #9

                  I have deleted my replies to you from the thread "Problems with feeder statistics and data sharing", as those were off topic.
                  It will be nice if you also delete your 2 off-topic posts (Post #30 and Post #31). Thank you.

                  How to Delete a post:
                  Click "Edit Post" >> Click Button "Delete" >> Check option "Delete Message" >> Click Button "Delete Post"


                  • #10
                    Well the Blue FlightAware dongle arrived today and so far its looking good. Before I was getting at a push 40/50 nm. So far I have seen 86nm which I have never been close to. For clarity I can confirm its the same Pi with the same antenna, all in the same position.

                    RTL Scan before the change

                    Same section from the Blue

                    The new scan shows data around 1090 but the old scan was more or less empty. The interference pattters didnt seem much different but I suspect the Mast near me (google maps says 59 meters away) could be the Tetra system for the Police which I think is around 450mhz
                    Last edited by markylondon; 2018-06-22, 21:33.


                    • #11
                      (1) The received 1090 Mhz signal strength depends upon:

                      (a) antenna
                      (b) antenna location
                      (c) amplifier (you already have one built into ProStick Plus)

                      Using a better antenna, and/or better location may improve plane count & maximum distance substantially. You can create a bench-mark by determining what maximum range is achieveable at your location:

                      What is the Maximum Range I can Get?

                      (2) Although ProStick Plus has a built-in filter, adding an external filter in most cases reduces interferencce and thereby improves reception.

                      Last edited by abcd567; 2018-06-22, 22:17.


                      • #12
                        I tried that page and if I had ideal conditions I should capture most of the UK, well all of England, and parts of Netherlands, Belguim and France.

                        But, I am far from ideal, the antenna is on the window sill (inside the house) of the spare bedroom facing SW. That being said I was getting an avg of 1500 planes per day at distances of 40 to 50 nm, now with this Blue Flightaware I am getting just over 2000 planes and distances of 80+nm on my flight radar stats so it was a definite upgrade for me.
                        Last edited by markylondon; 2018-06-25, 07:29.