Poor GPS Fix
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@Rodrigo-Betances , yes, absolutely. I will provide your name to the team.
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@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.
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@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.
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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
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@ROBERT-JUDD Nice! Hopefully we can get one of those kits too! Green with envy over here haha
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@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 onNone 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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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.
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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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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!
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Hello everyone,
We’ve been following this discussion with great interest — especially the insights about the mast kit and the copper shielding solution. We also tried similar approaches on our side and wanted to share our results to contribute to the thread.
We purchased four Starling 2 Max drones for our project at the beginning of the year, and like others here, we are experiencing difficulties with GPS stability outdoors. To mitigate interference, we designed and 3D-printed our own GPS mount to move the antenna away from the main body, and we added a copper shielding layer around it.
We then tested the u-blox M10 GPS outside, under clear sky conditions, with the drone powered on (connected via Wi-Fi to use VOXL-Portal). Over about 10 minutes, the best observation we captured showed 18 satellites with an average SNR around 30–35 dB.
However, despite these results, we still cannot achieve a stable outdoor localization, which currently prevents us from flying the drones properly outside. At this point, we’re unsure whether the problem comes mainly from the GPS performance or possibly from the barometer.
We’d really appreciate:
- Being included in your support list for this GPS issue, since it affects multiple units on our side (as mentioned by @Alex-Kushleyev).
- Any guidance or recommendations on how to debug further (extra shielding, hardware setup, barometer validation, software settings, etc.).
Thanks a lot to the ModalAI team and to the community for the shared ideas — we hope our feedback helps others as well.
Best regards,
Quentin
