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    Poor GPS Fix

    PX4 Autonomy Developer Kit
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    • Rodrigo BetancesR
      Rodrigo Betances
      last edited by

      @Alex-Kushleyev said in Poor GPS Fix:

      I believe your name is already on the list to receive it.

      Anyway we can get on that list too? We received our starling 2 max nearly a month ago now and have only recently been able to test it. We're happy with everything but the GPS problem makes this product borderline unacceptable. We just had a meeting where we decided to hold off on ordering 5 more starlings because of this issue!

      Alex KushleyevA ROBERT JUDDR 2 Replies Last reply Reply Quote 0
      • Alex KushleyevA
        Alex Kushleyev ModalAI Team @Rodrigo Betances
        last edited by

        @Rodrigo-Betances , yes, absolutely. I will provide your name to the team.

        ROBERT JUDDR 1 Reply Last reply Reply Quote 1
        • ROBERT JUDDR
          ROBERT JUDD @Alex Kushleyev
          last edited by

          @Alex-Kushleyev That's just the PETG plastic mount that I 3D printed in the picture. I'm using the GPS receiver that came with my Starling 2 Max from ModalAI (3DR taoglas).

          Here's what I'm seeing in voxl-portal with my modification. ModalAI's GPS kit should arrive today, and I should be able to send you results for that in a few days.

          satellites.png

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          • ROBERT JUDDR
            ROBERT JUDD @Rodrigo Betances
            last edited by

            @Rodrigo-Betances @Alex-Kushleyev @somalley OK I received the mast GPS fix from ModalAI and I've installed and tested it. I do get more satellites and the signal is enough to get a GPS lock, so I'm clear to fly at this point. The signal still seems a bit low but maybe that's just my location. I do have a clear view of the sky but there are tall trees not far away that may block satellites below roughly 45 degrees from the horizon.

            IMPORTANT: The mast kit shipped with a ca. 10cm 6-pin cable with female JST GH connectors on each end. There is no way to connect that cable to the existing connector, and the cable itself is too short to reach the VOXL2 connector. I would suggest that one end be shipped with a male connector. Otherwise customers will need to make their own cable as I did.

            Thanks for your help. Looking forward to reports from others.

            drone-with-gps-fix.jpg

            modalai-fix.png

            Alex KushleyevA Rodrigo BetancesR S 3 Replies Last reply Reply Quote 0
            • Alex KushleyevA
              Alex Kushleyev ModalAI Team @ROBERT JUDD
              last edited by

              @ROBERT-JUDD ,

              Yes, we are aware about the cable mismatch (sorry, the shipment was rushed a bit, but we will get it right!)

              Regarding the satellite SNR, yest it still looks low. I would normally expect 10dB higher.

              Are you able to test with disabled 5G modem? maybe pop out the 5G card or shut it down via a pin ( think we discussed how to do this long time ago).

              I just received the same kit and will be testing it today and compare with my initial implementation of the mast. Will report back..

              Alex

              ROBERT JUDDR 1 Reply Last reply Reply Quote 0
              • Rodrigo BetancesR
                Rodrigo Betances @ROBERT JUDD
                last edited by

                @ROBERT-JUDD Nice! Hopefully we can get one of those kits too! Green with envy over here haha

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                • ROBERT JUDDR
                  ROBERT JUDD @Alex Kushleyev
                  last edited by

                  @Alex-Kushleyev This morning I tried to determine if the 5G service affects the GPS signal. I removed the SIM card, turned off the power using the commands below, and verified that I had no 5G service. I also tried various combinations of these, and I also tried disabling voxl-modem and rebooting.

                  voxl-gpio -m 1 out
                  voxl-gpio -w 1 0 # power off
                  voxl-gpio -w 1 1 # power on

                  None of these had any effect on the GPS signal. It remains essentially the same as the graph I sent yesterday (20-35 db on ca. 10 satellites). This does get a GPS position lock, however, so probably I can fly.

                  Looking forward to your results.

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                  • S
                    somalley @ROBERT JUDD
                    last edited by

                    @ROBERT-JUDD @Alex-Kushleyev

                    We built upon the shield/cone concept since it showed promise and worked to eliminate any tiny gaps and cracks where EMI could potentially leak through. We designed and 3D printed a cone that would come together on both sides of the GPS antenna mount with enough spacing for them to slide around the posts. The inside of the cone and some of the post had copper tape applied to it. Aim of this is to shield the GPS antenna from all RF below the cone and only receive RF from above. As you can see from the screen captures, the results are very promising. I think my team and I can now move forward in testing that was previously blocked by the poor GPS performance. Hope this helps and inspires some other fixes.

                    You may want to consider a small RF shield cone on top of your mast.

                    Here are the results from our custom shield and testing.

                    b7882c75-c941-4022-9e39-81d67600eb9e-image.png
                    bf2babfa-3bea-4fb7-b795-f1c2109876b6-image.png
                    ca215b4b-4d49-4065-a970-d856fad9253b-image.png
                    2bc59b8a-3f2d-4dee-a765-5547e174f611-image.png

                    Alex KushleyevA 1 Reply Last reply Reply Quote 1
                    • Alex KushleyevA
                      Alex Kushleyev ModalAI Team @somalley
                      last edited by

                      @somalley ,

                      Very cool, thank you for sharing. We will try something like this.

                      Please note that we have observed that the wifi dongle, which is right under the gps receiver, causes some interference as well. Can you please try to repeat your test by unplugging the dongle completely?

                      A workaround to move the dongle to a different location is to use a different USB breakout board. Instead of M0141, use M0151 with a cable (JST GH to USB A Female).

                      Alex

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                      • Kyle GajadharK
                        Kyle Gajadhar
                        last edited by Kyle Gajadhar

                        Hey @Alex-Kushleyev how can I get on that mailing list for the ModalAI sanctioned mast? I designed and 3DP two mounts and used a carbon fibre rod, along with a copper laminate board and seen great improvement in GPS count (see image and screenshot).
                        Did a couple test flights with this set up and everything ran smoothly. I'll have a better peace of mind with an official mast though.

                        Looking forward to your response!

                        mast.PNG matandemi.PNG

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