NRF9160: GPS Tracking satellites, but can't get fix.

Hi, we have a custom board using the nrf9160, running modem firmware 1.1, and using the nrf9160_gps driver.

Sometimes we see messages like this:

Tracking: 8 Using: 0 Unhealthy: 0

Where the GPS is tracking satellites but is not using any, and never gets a fix. Eventually we time-out and stop the GPS. But this behavior continues until the next device is restarted.

Is this a bug with the modem firmware? Is there any fix for this.

Thanks

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  • Hello, 
    I've been discussing your schematic with one of our HW engineers, and there is one potential issue: when the LTE radio is operating, the RF signal can intermodulate in the GPS LNA input stage and create unwanted harmonics. You should be safe either using an LNA with an integrated filter or by adding a filter on the input of the LNA.

    Your design deviates from the reference design from the LNA vendor. You can also test with an external antenna. And please, test outside in open space.

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