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  • Polar Plot anomalies

    I started using the new FR Feeder for Windows about 10 days ago so I'm still feeling my way a bit. I'm using a DVT stick and everything seems to be working OK, but what I am seeing on the Polar Plot "Range" indicator doesn't make sense. On most days I am seeing a Range value of 300-400nm on at least one compass point, and sometimes on two or three points. My location isn't particularly good here and the aerial could be better positioned (which I will deal with), so a realistic value for the Range on most compass points would be around 100nm. I really don't think I'm seeing aircraft from 300-400nm every day - I doubt if my setup would ever do that.

    The colour-coded values in the Polar Plot segments, showing the count of positions for each compass point, make sense and match my expectations from what I'm seeing on Radar View. The "Maximum distance" figure in the page heading also fits what I am seeing (and it is nowhere near 400nm!).

    I assume that I'm getting the occasional anomalous number that is feeding the Range indicator figures and nothing else, but I don't know where the fault lies - is it here, and if so how can I fix it, or is the problem at the FR end?

  • #2
    Maybe my question wasn't clear enough, so I've put some examples of these anomalous plots here:-

    https://dl.dropboxusercontent.com/u/...eral/Plots.jpg

    I'm seeing these big distances - 350-400nm - on the distance line in the Polar Plot every day. That sort of performance isn't realistic with my current setup. The Sector plots, showing the count of positions reported by distance, all show what I would expect to see from my setup with nothing in the >200nm band, and the maximum distance shown on the info page on FR24 does not exceed 100nm. Anyone any idea why I'm seeing these big distances reported?

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    • #3
      I see the same distance anomalies almost daily. Don't think its any big deal. If it ain't broke it doesn't need fixin'.

      !fr242.png
      F-KDAG1

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      • #4
        Thanks. If others see the same thing then at least that indicates the problem isn't at my end, which is what I was asking - so, as you say, I don't need to fix it.

        If spurious values in the Polar Plot are common then it does limit the value of that line, though. I've been running VirtualRadar for a couple of days now, and that has given me a good idea of my true coverage (which I'm sure can be improved!).

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        • #5
          I saw this within a few days of running my Pi and DVB. But not on the beast. So its probably related to those if noone else sees them with other hardware
          Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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          • #6
            Originally posted by Oblivian View Post
            I saw this within a few days of running my Pi and DVB. But not on the beast. So its probably related to those if noone else sees them with other hardware
            Seeing this daily with my FR24 box, I think it is because the cable has got water in as the genuine detection distance has also dropped dramatically in the last few months.
            image.jpg
            FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

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            • #7
              I had one of these recently and posted in another thread about it and was advised this has been happening often. However, I decided having looked at the Polar Plot I would compare to actual aircraft data in the FR24 Page as it was in an area I normally only achieve around 100nm.

              I am based in Antas, Spain and the Aircraft it picked up was over Djelfa in Algeria, some 339.8km (183.4nm) as the crow flies according to http://www.freemaptools.com/how-far-is-it-between.htm
              If life is a stage, most of us are unrehearsed...!

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              • #8
                I can understand there will be occasional extreme contacts because of unusual radio propagation conditions, but I think they are fairly unusual.

                When the plot you describe happened, can you remember whether the Maximum Distance figure on the Stats page showed your 183nm? There have been two occasions when my Maximum Distance figure has matched my longest Polar Plot, and I'm assuming those were "genuine" long-distance contacts. Other than those two occasions, the Maximum Distance figure has been in line with what I'm seeing on RadarView and in VirtualRadar but much less than the spike(s) on the Plot line. It's partly for that reason that I'm questioning the accuracy of the spikes on the Plot line - the "Maximum Distance" figures doesn't agree with them.

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                • #9
                  Originally posted by steve-b View Post
                  I can understand there will be occasional extreme contacts because of unusual radio propagation conditions, but I think they are fairly unusual.

                  When the plot you describe happened, can you remember whether the Maximum Distance figure on the Stats page showed your 183nm? There have been two occasions when my Maximum Distance figure has matched my longest Polar Plot, and I'm assuming those were "genuine" long-distance contacts. Other than those two occasions, the Maximum Distance figure has been in line with what I'm seeing on RadarView and in VirtualRadar but much less than the spike(s) on the Plot line. It's partly for that reason that I'm questioning the accuracy of the spikes on the Plot line - the "Maximum Distance" figures doesn't agree with them.
                  Hi Steve, in the direction it was picked up, the average is between 50-100nm due to the Carboneras Mountain Range, my longest distance is nearly always the same in a different direction at 212nm. As it recorded a 'location', I would assume FR24 logged it even though it was nearly double the distance for the direction it was received from.

                  I will be going off-line for a short period today as I have just run a 20m Power Cable and 20m Cat5e Cable from my apartment to the roof that will enable me to get all the FR24 Kit outside into a weather proof IP55 box and mount the antenna 3-6 metres higher. A friend who is a surveyor had done some calculations about height and distance and believes this will get me over the mountains and improve the data collected from the two directions (South/South East) that are blocked...watch this space!
                  If life is a stage, most of us are unrehearsed...!

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                  • #10
                    Hope it all goes well! I'm waiting to do some work in our roof space, after which it should be possible for me to get an extra 2-3m of height. This area is only about 6m above sea level, though, and is almost surrounded by hills, so I'm never going to see very long distances.

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                    • #11
                      Hi all ! I'm new in this forum, but I use FR24 to 2010.
                      I have a question for all : how to find the big largest aircraft, the Antonov an -225 Mriya?

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                      • #12
                        Originally posted by steve-b View Post
                        Hope it all goes well! I'm waiting to do some work in our roof space, after which it should be possible for me to get an extra 2-3m of height. This area is only about 6m above sea level, though, and is almost surrounded by hills, so I'm never going to see very long distances.
                        Well we got half way through the move before the rain set in and we had to give up on the installation of the new mast, however even with the Antenna in a temporary location todays reporting a maximum distance of 237 so an increase of around 20nm in that direction, however we have an average increase of over 80nm in 2 other directions... the temp location is only 2 metres higher than it was before, so when the mast goes up with the Antenna on it, we are expecting much better distances all round.

                        Even though the direction that has not seen an increase in distance is disappointing ALL directions are up 50% on the volume of positions reported so clearly the additional height is allowing the antenna to pick up more signals previously blocked by the Mountain Range.
                        If life is a stage, most of us are unrehearsed...!

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                        • #13
                          Due to bad weather we delayed installing the new mast and as a temp solution, a hole was cut in the bottom of an old Roasting Pan, FR24 Mast fitted to this and it was mounted on the roof on top of a concrete air vent and we got better results immediately from the antennas new temporary home.

                          However, today I got what I initially thought was one of the random plots experienced by myself and others at time, but when I checked, no, it was no anomaly, FR24 reported Max Distance at 368nm (681.5km)... checking the data, it had 7 Hits at 366nm, 13 at 360nm and 144 at 358nm.


                          *edited to add second image.
                          Last edited by DemonLee; 2015-10-09, 16:28.
                          If life is a stage, most of us are unrehearsed...!

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                          • #14
                            Good news, and I'm sure it will be even better when the mast is up. I have had two "spikes" which I think were real because they are reflected in the Maximum Distance figure, but the rest aren't.

                            Pardon my ignorance, but how did you check the data to confirm the long-distance hits?

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                            • #15
                              Pardon my ignorance, but how did you check the data to confirm the long-distance hits?
                              Hover over the spike in the Highcharts histogram.

                              It helps to visualize coverage if you imagine a torus shape:

                              !!horntorus_hexagonal.jpg


                              There's a lot of real estate 50 to 100 NM out from your location, which begins to shrink as you approach the far edge of the torus.
                              F-KDAG1

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