GNSS very bad reception / unreliable fix

[Markus Schlittenbauer]

We are using the Asset Tracker Template with on a nRF9151-SMA-Devkit, using the enclosed external GNSS antenna outdoors (out of the window) and the GNSS reception is very bad.
Even when the device is using the A-GPS and M-Cell location, the GNSS fix sometimes takes minutes to get, even when there is very little obstruction

Are we missing an option to activate the power for the LNA ? (I assume this is already activated in the Asset Tracker Template ?)

What is the recommended setting for a 10 second tracking interval (constantly updating the GNSS fix and sending the latest GNSS fix every 10 seconds) ?

Thanks a lot!

[Nishant Gaurav]

Hi Markus,

What you are observing is expected behavior on nRF91 devices due to LTE and GNSS RF coexistence.

this can be avoided somehow,

• A-GNSS assistance data — The single biggest improvement. With fresh ephemeris injected, re-acquisition after an LTE interruption drops from ~20 seconds to 1–3 seconds.
• Minimize LTE TX duration — Shorter transmissions mean shorter GNSS blackouts. Use small payloads and efficient encoding.
• Don't call nrf_modem_gnss_stop() / start() around LTE events — Let the modem manage the arbitration internally rather than doing a full API-level restart.