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Comparing ADS-B 1090MHZ Antennas, 2.0dBi antenna and 12.0dBi

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  • Comparing ADS-B 1090MHZ Antennas, 2.0dBi antenna and 12.0dBi

    Hello,

    I bought 2 PCB antennas from AliExpress

    2.0dBi
    https://www.aliexpress.com/item/4000863761443.html

    12.0dBi
    https://www.aliexpress.com/item/1005004246131792.html

    The 2.0dBi gives me a max distance of 289nm, logging around 800-900 aircraft per day

    The 12.0dBi gives me a max distance of 110nm, logging around 400-500 aircraft per day

    I am using the exact same equipment , just swapping the antenna, why should the low gain antenna out perform the high gain antenna?

    Thanks


  • #2
    Very interesting indeed... Is it possible to take apart the 12.0dBi antenna and see what's inside?

    Comment


    • #3
      Originally posted by dkyyz View Post
      Very interesting indeed... Is it possible to take apart the 12.0dBi antenna and see what's inside?
      inside is a pcb, it looks like 4 antennas stacked on the pcb and the extra piece of wire.
      You do not have permission to view this gallery.
      This gallery has 3 photos.
      Last edited by g4ea5; 2022-07-12, 08:16.

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      • #4
        The easy answer is: it's not 12 dBi, who would have thought sellers would ever lie.

        The design could probably have better performance but likely they used the wrong PCB material or bad dimensions.
        Thus the antenna is just utter garbage and the sellers lie.

        Maybe you're using it wrong, using bad coax.

        Comment


        • #5
          Originally posted by wiedehopf View Post
          The easy answer is: it's not 12 dBi, who would have thought sellers would ever lie.

          The design could probably have better performance but likely they used the wrong PCB material or bad dimensions.
          Thus the antenna is just utter garbage and the sellers lie.

          Maybe you're using it wrong, using bad coax.
          Im not using it wrong and its not a bad coax because its the same coax which feeds the 2dbi PCB antenna which works very well.
          The "so called" 12dbi antenna is probably just badly made, probably designed using computer software and sent for production without testing.
          It would have been nice if it worked.

          Comment


          • #7
            I will give one of those a try, Thanks

            Comment


            • #8
              Originally posted by g4ea5 View Post
              inside is a pcb, it looks like 4 antennas stacked on the pcb and the extra piece of wire.
              Yea, that doesn't look too promising... can you measure the patches on PCB and the extra piece of wire to see if there are any relationships to the 1090MHz wavelength?

              Comment


              • #9

                Originally posted by dkyyz;neach wide metal part measure 20mm x 72mm

                and each of the thinner metal parts measure 20mm x 72mm
                214358

                Yea, that doesn't look too promising... can you measure the patches on PCB and the extra piece of wire to see if there are any relationships to the 1090MHz wavelength?
                On the front side of the antenna each of the wide metal parts measures 20mm x 72mm and each of the thinner metal parts (elements) measures 3mm x 72mm

                On the front side there is continuity to the centre conductor of the SMA socket.

                On the back side of the antenna each of the wide metal parts measures 20mm x 76mm and each of the thinner metal parts (elements) measure 3mm x 76mm

                The piece of wire (element) measures 1mm x 76mm

                There is no continuity between each side of the antenna and its not connected to the outer part of the SMA socket.

                Perhaps it just needs soldering together correctly?
                Do you think each side of the antenna should be soldered together?
                or maybe solder the back side of the antenna to the outer conductor of the SMA socket?

                Thanks

                Last edited by g4ea5; 2022-07-14, 14:27.

                Comment


                • #10
                  I am no expert on antennas. Maybe someone can give their 2 cents.

                  I am not sure why the front and back have a slightly different 'length' (72mm vs 76mm) but the pattern may be kinda like a coco antenna design?

                  And 72 (or76)mm is a bit longer than 1/4 wavelength. If I am not mistaken if you factor in VF it should be even shorter, right? Is your antenna like (a)?



                  Comment


                  • #11
                    Could very well be that the SMA connector isn't properly soldered.

                    Can you remove the last piece of plastic and photograph it?

                    Comment


                    • #12
                      Originally posted by dkyyz View Post
                      I am no expert on antennas. Maybe someone can give their 2 cents.

                      I am not sure why the front and back have a slightly different 'length' (72mm vs 76mm) but the pattern may be kinda like a coco antenna design?

                      And 72 (or76)mm is a bit longer than 1/4 wavelength. If I am not mistaken if you factor in VF it should be even shorter, right? Is your antenna like (a)?


                      Thanks, Yes its A, update after soldering coming soon.



                      Originally posted by wiedehopf View Post
                      Could very well be that the SMA connector isn't properly soldered.

                      Can you remove the last piece of plastic and photograph it?
                      I have soldered it and its now high on the roof so I cant photograph it.

                      I managed to borrow a hackrf and run a spectrum analysis, will update results soon

                      Thanks

                      Comment


                      • #13

                        See images

                        Spectrum analysis of the 12dbi antenna before soldering the back elements to the outer part of the SMA, resonant at 1340-1360 MHZ

                        Spectrum analysis after soldering the back elements to the outer part of the SMA, resonant at 1075-1125 MHZ

                        So now I am actually getting around 25 db over the noise floor at 1090mhz

                        However in real life the antenna does not appear to perform any better than the so called 2dbi antenna

                        The 2dbi antenna apparently is 75 ohms and yes it does perform much better with a 75 ohm cable.

                        The 12dbi antenna is 50 ohms but it doesn't seem to make any difference if I use 50 ohm or 75 ohm cable.

                        Also If I use the amplifier with the 12dbi antenna it makes no difference at all.

                        If I use the amplifier with the 2dbi antenna it doubles the distance.

                        Its all very confusing.
                        You do not have permission to view this gallery.
                        This gallery has 2 photos.

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                        • #14
                          I am scratching my head too!

                          And yes, the filter+LNA I ordered from AliExpress, both SMA connectors weren't soldered to the back pcb (ground plate) too. I have to solder that myself (and learned that large copper on PCB is a very good heatsink!)

                          Ordering stuff online oversea these days is a bit of a gamble even with many so call positive reviews.

                          Comment


                          • #15
                            Originally posted by dkyyz View Post
                            I am scratching my head too!

                            And yes, the filter+LNA I ordered from AliExpress, both SMA connectors weren't soldered to the back pcb (ground plate) too. I have to solder that myself (and learned that large copper on PCB is a very good heatsink!)

                            Ordering stuff online oversea these days is a bit of a gamble even with many so call positive reviews.
                            Cheap and cheerful products but no quality control.
                            I also ordered a filter and LNA from AliExpress but it only lasted a few days
                            The best so far has been the little 2dbi pcb antenna with a sat tv amp.

                            As for the so called 12dbi antenna I continue to scratch my head. perhaps some mismatch in impedance?
                            Its unusual how the impedance of the cable on this particular antenna doesn't appear to make any difference.
                            After soldering it I have at least proved it is resonant at 1090mhz
                            Do you know how I can measure the impedance of the antenna? Perhaps it needs correctly matching? it must be way-off frequency by the time the signal has travelled through the cable to the rtl?
                            Last edited by g4ea5; 2022-07-14, 19:34.

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