ModalAI Forum

@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.

@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.

@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.

@Alex-Kushleyev Thanks for the info. Yes your team has shipped a GPS mast kit to me and it should arrive tomorrow. Thanks very much for making that happen. I'll try it and let you know the results in the next few days.

In my implementation I did not have two antennas, only one. I did try the GPS viewer in voxl-portal and it worked great, much more convenient than Ublox Ucenter. The GPS signals I received were about 20-30dB in open sky with up to 9 satellites. Much better than before but not enough to get a lock. I did not power up the RC transmitter because I'm connecting exclusively with 5G Google Fi when the drone is outside (inside I use the USB cable). I've also removed the WiFI USB device just to limit the possibilities.

Looking forward to testing the mast kit.

Bob

@Alex-Kushleyev @somalley

PS there is a piece of copper foil under the GPS receiver, not visible in picture.

@Alex-Kushleyev @somalley ,

Alex: Thanks for the reply. I tried to duplicate your workaround, see picture. The GPS signal did improve to the point where I could see 9-10 satellites, but I could not get a position lock and still could not fly.

Question: in the picture from your post (see below), what is the object that I've circled in blue? Is that something that might explain why your GPS signals are much better than mine?

@somalley @Alex-Kushleyev Thanks for referring to my March 1, 2025 post regarding the GPS problem:

Starling 2 Max no GPS data

ModalAI Support, I received a new Starling 2 Max a few days ago, and overall it's great, but I'm having a problem with GPS. Basically, the drone appears to N...

ModalAI Forum (forum.modalai.com)

Overall I'm a big fan of ModalAI, but in my opinion this product contains a fundamental design flaw (complete loss of GPS position data due to EMI) that should have been detected and corrected early in the design testing phase. Moreover, that fatal design flaw has remained uncorrected for many months now, and I have received no information about if/when a permanent fix will be available. Our company spent over $5,000 on a Starling 2 Max, and it remains largely unusable due to this problem.

Alex Kushleyev at ModalAI has in general been very responsive, and has developed a temporary fix that customers can implement on their own, which I genuinely appreciate. But the fact remains that ModalAI inexcusably sold a product with a fundamental design flaw, and has not offered a permanent fix for many months now. In my opinion, at this point a permanent fix should be one of ModalAI's highest priority if they want to avoid a significant loss of customer confidence.

I would suggest that, as a first step, ModalAI should create a new post dedicated to providing ongoing fix updates and timelines, and to systematically update that post on the same day and time each week until a permanent fix is made available.

Thank you for your consideration.

Robert Judd

@CJoseph said in Starling 2 Max no GPS data:

Hey @Alex-Kushleyev,

I'm attempting this short term fix for a project I'm working on and I'd like to keep in line with recommended practices.

Can you kindly provide the .stl file used for the 3DP mount and also inform me of the material you used to 3DP?

Thanks in advance!
Christopher Joseph.

@Alex-Kushleyev: I'm also planning to repeat your modification, and the .stl file would be very helpful to me as well. I tried a different modification yesterday but it didn't work, so copying yours is my next step.

Thanks for your help.
Bob Judd

@Alex-Kushleyev Circling back on this problem now, has your team identified the source of the EMI? Can I expect a long term fix that will allow me to fly my Starling 2 Max?

Thanks

@Alex-Kushleyev Thanks for the update. I had to pivot away from this project and plan to revisit it when ModalAI has a long term fix. Have your colleagues made any progress identifying the source of the EMI?

Thanks again for your help.

@Alex-Kushleyev Did you have a test flight yet? How did the GPS perform while flying?

Thanks

@Alex-Kushleyev Very interesting, thanks for the update.

Regarding the EMI from the Commando 8 transmitter, I wonder what would happen if you removed the Ghost Atto receiver and antenna from the drone. Maybe somehow they are involved in the EMI.

Noise from the 6-conductor cable is also interesting, I wonder if passing them through an RF shield would make a difference.

Please let me know the results of your test flight. If it's successful I may do something similar and repeat your testing.

What ideas do you and your team have for a long term solution? Do you have access to something like SignalHound equipment to search for the source of EMI?

Thanks
Bob

@Alex-Kushleyev Have you made any progress with this yet? Please let me know if/how I can help.

@Alex-Kushleyev Got it, thanks. FYI here's an interesting graph regarding the frequency of the EMI from a prior post:

Problem acquiring GPS satellites (possible voxl2 board EMI?)

Hello, We have a Starling 2 and a few Starling 2 Max's which have issues acquiring GPS. We tested on several occasions outside with clear skies. However, we...

ModalAI Forum (forum.modalai.com)

@Alex-Kushleyev Thanks for the reply, and yes, I'm happy to work with you to find a solution. As an attempt to improve SNR, I took the STEP files and created a "stretched" 3D-printed version of the GPS mount, see below, but I haven't had a chance to install it yet. Based on some previous testing I think the added distance will improve SNR somewhat, and adding some shielding should also help, but I think the best long term solution would be to find the source of EMI and target that. I don't have the equipment or knowledge to do that, however.

Please keep me posted, and let me know if there's any way I can contribute. Thanks for your help!

@Alex-Kushleyev Here are the results of testing with a brand new GPS from a different manufacturer (https://holybro.com/products/micro-m10-gps?variant=42981482954941). The GPS is in the same position as the original, but connected to u-center. As with prior tests, Lepton is disconnected and ALFA is removed.

Top u-center screen shot is with drone powered OFF, bottom is drone powered ON. To me this Holybro GPS looks about the same as the 3DR GPS, i.e. satellite signals drop significantly with drone powered ON. Not shown are results where I found that the satellite signal increased significantly when I moved the GPS module farther away and/or added shielding.

What do you suggest as next steps?

Thanks for your help.

@Alex-Kushleyev will do, thanks!

@Alex-Kushleyev said in Starling 2 Max no GPS data:

Let me check with the team what the expected signal level is when a properly working Starling 2 Max is receiving GPS.

Have you had a chance to check on this?

FYI in the meantime I've purchased 3 additional GPS modules from different manufacturers, and will evaluate them using u-center and the drone when they arrive.

I need to get this problem fixed somehow - can't fly far without a GPS!

@Alex-Kushleyev 3DR says the replacement GPS won't be shipped until next week. Are there any useful tests I can run while waiting, eg. power down selective subsystems and observe GPS signal via u-center? I did hold the current (potentially defective) GPS module in my hand and move it around the drone while observing signal strength in u-center, but it wasn't clear to me where the interference was originating from. Open to suggestions. Thanks for your help.

@Alex-Kushleyev OK, just now I repeated the test of GPS signal with/without powering up the drone and the results were the same as yesterday: roughly 10 dB drop in GPS signal when drone is powered up. At that point I shut down the voxl-camera-server (systemctl stop voxl-camera-server), meaning no power to any cameras, and there was no apparent change (still 10 dB down). I did double check that the change happened via "voxl-inspect-services" (camera server not running).

So here is the current status:

With GPS module connected to u-center2 (not connected to drone but physically in the same position on drone frame):

0. Everything below is Lepton connector removed and ALFA USB wifi removed

1. Drone powered off: good GPS signal (14-20 satellites tracked, most 40-45 dB)

2. Drone powered on: GPS signal drops about 10 dB

3. Drone powered on, 5G modem powered off: no improvement

4. Drone powered on, 5G modem powered on, all cameras powered off: no improvement

Any other subsystems I can power down and/or unplug? I'll try the new GPS module when it arrives hopefully Monday.