I have been using mentioned module above with passive antenna for GNSS connection on identical platforms. I somehow was able to establish GPS connection on 2 units, but was not so lucky on other units. I checked the configurations commands, hardware ,firmware and other usual suspects but could not find any difference between the units. I tried AGNNS with LTE support, XTRA assistance, SUPL assistance and no luck. I am using VisualGPSview 3rd party tool to verify ongoing process but cannot detect single satellite signal with around 1 hour GNSS active waiting time let alone tracking it. Working 2 units were also having the same issue, but somehow after they are managed the connection, they no longer need any assisted GNSS to establish a connection. Any help/idea would be great, I just want to collect some different thoughts about how I can proceed further and what to check. Thanks in advance!
Dear @Dorado ,
Thank you for the detailed description.
Based on what you shared, the most important clue is that the failing units do not detect even a single satellite after a long GNSS run time. When the receiver shows no satellites at all, the issue is usually not related to the assistance method itself. XTRA, SUPL, or LTE-assisted GNSS can help reduce time to first fix, but they cannot compensate for the absence of a usable RF signal at the GNSS antenna input. For the EM120GL-K family, GNSS is routed through the DRx/GNSS antenna interface, which is a 50 Ω RF path. Any issue on that path can directly result in zero visible satellites.
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Since you are using a passive antenna, I would first focus on the antenna path and test environment rather than the GNSS assistance configuration. A passive antenna is more sensitive to installation loss, cable quality, connector condition, and sky visibility because it does not provide front-end gain.
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The fastest way to isolate the issue is to place one working unit and one failing unit in the same open-sky environment and swap the GNSS antenna and cable between them. If the problem moves together with the antenna or cable, then the root cause is in the RF path. If the same unit continues to fail even when using the known-good antenna path, then the next likely suspect is the module-side GNSS connector contact or hardware variation on the DRx/GNSS receive path.
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The fact that two units eventually managed to obtain a fix and later no longer needed assisted GNSS also points more toward a reception-related condition rather than a command or software issue. Assistance improves acquisition speed, but it does not replace the need for sufficient satellite signal strength at the receiver input.
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Please also check the antenna layout and coexistence condition carefully. If LTE is active during GNSS testing and the GNSS antenna is placed too close to the cellular antenna, poor isolation can significantly reduce GNSS sensitivity. This is especially important when using a passive GNSS antenna.
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At this stage, the key items to verify are whether the test is truly performed under open sky, whether the failing units behave differently after swapping in a known-good antenna and coax assembly, whether the DRx/GNSS connector and cable insertion are fully reliable, and whether the GNSS antenna placement and LTE/GNSS isolation are identical across all units.
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If possible, please also share the GNSS NMEA output or AT logs from one working unit and one failing unit under the same outdoor condition. The main point to compare is whether the failing units ever report any satellites in view at all. If they remain at zero satellites consistently, then the issue is very likely on the RF side rather than in AGNSS, XTRA, or SUPL configuration.
From your current description, the antenna path, RF condition, or platform-level reception difference is the most likely direction to investigate first.
Best Regards,
Aghelan