nRF9160DK - Tracking satellites but not getting fix

[PeterIoT]

Hello Nordic team,

We're experiencing a GNSS issue with our nRF9160-DK (PCA10090 1.1.3 2024.44) and would appreciate any guidance you can provide.

About 4 days ago, we were successfully obtaining GNSS fixes in 30-50 seconds during cold starts outdoors with clear sky visibility 1-2 times. We continued development work, and now the same hardware is unable to acquire any fix even after 600+ seconds of continuous operation.

We're developing our firmware in Rust using the nrf-modem and embassy-nrf crates. Our GNSS configuration includes:

AT%XCOEX0=1,1,1563,1587

Looking at the NMEA output from a 600-second test run 30511.log.txt(conducted outdoors, clear sky, walking around), we can see:

• Satellites are being tracked
• SNR values are abnormally low (typically 24-29 dB, occasionally reaching low 40s)
• No position fix is ever acquired (GPGGA shows fix quality 0, GPRMC shows status "V" for invalid)
• GPGSA shows mode 1 (no fix) with DOP values at 99.99

Steps taken:

• Performed AT%XFACTORYRESET=0 before running the code that produced these logs
• Tested outdoors with clear sky view for extended periods
• Verified LNA and MAGPIO configuration

We are currently in the process of acquiring a Segger to potentially update (or downgrade) the modem firmware.

• Could the abnormally low SNR values indicate a hardware issue (LNA failure)?
• Could updating the modem firmware resolve not being able to get a fix?
• What diagnostic steps would you recommend to isolate whether this is a hardware vs. firmware issue?

Logs are attached above and trace-2025-10-28T17-04-27.467Z.mtrace is here. Any insights into what might have changed or what we should investigate would be greatly appreciated.

Thank you for your assistance!

[Øyvind]

Thanks for testing! I've forwarded this internally to get more feedback on possible cause. 

Kind regards,
Øyvind

[Øyvind]

Hello again, 

Upon reviewing the modem log, it was observed that LTE is active. However, +CEREG notifications have not been subscribed, and therefore are not visible in the log. Power Saving Mode (PSM) has been requested, albeit without any specific parameters. As a result, the default configuration is applied, which includes an active time of one minute. The network accepts this configuration, and PSM with a one-minute active time is consequently utilized.

When GNSS is initiated, LTE activity intermittently disrupts GNSS operation until the modem enters PSM following one minute of inactivity. After this transition, the GNSS signal levels are notably low. Although the GNSS module is able to track some satellites, it fails to decode ephemerides for a sufficient number of them.

An examination of the Automatic Gain Control (AGC) level indicates that it is slightly low, suggesting the possibility of interference. It is recommended to verify the testing environment, specifically, the physical location of the device during testing. For instance, interference from nearby electronic devices such as laptops could be a contributing factor.

Updating the modem firmware to the latest version is advisable, as recent releases include significant improvements to GNSS functionality. However, it should be noted that firmware updates alone will not resolve the issue of low signal levels. It is understood that the device is utilizing the onboard GNSS antenna provided with the development kit (DK). Please verify if external or onboard antenna is used.

[PeterIoT]

Sorry for the late response.

During last weekend we managed to solve the problem. The issue was that the device was too close to the laptop. Upon switching to a longer cable and keeping around 1m distance from the laptop, we are able to get fixes without problems in a reasonable 30-60sec interval.

Thank you for the help.

[Øyvind]

I'm glad we were able to to help! Good luck in the ongoing testing, and let us know if you get any further or other issues.

Kind regards,
Øyvind