nrf9160 GNSS not working... frustrating...

[Richard W Mincher]

I am using the Sparkfun thing plus nrf9160 feather with SDK 2.0.0 and modem firmware 1.3.2.

Ultimately I would like to get LTE working along with GNSS, however, I can't even seem to get your GNSS sample code to work reliably.  The "Tracking" output of the demo typically hovers around 1, and "using" is zero.  I have gotten it to work on rare occasions, but it is the exception rather than the rule.  Terrible performance even with clear sky views.

I've seen others expressing frustration with performance too, but haven't seen much of a response other than "it should work" and "It should work with LTE."

How do I solve this problem?  I was hoping that the latest modem FW and SDK would help, but no such luck.

Is there an issue with the feather board?  Noise, layout, etc?  

Any particular relatively inexpensive antennas you suggest I try?

Thank you.

[Craig12]

Richard,

Can you please provide details of the GPS antenna you are using?

For reference, I have found the schematic for the nRF9160 Thing Plus at
https://cdn.sparkfun.com/assets/5/7/c/a/c/nRF9160_Thing_Plus.pdf

[Craig12]

Thanks Richard.

Just to clarify, I'm a third party developer - not affiliated with NordicSemi. But we have designed our own nRF9160 board and have done some real world GNSS antenna testing (as late as Friday) so I hope I can offer some practical advice.

When I'm at the desk writing code, I use one of these in the window:
www.digikey.com.au/.../6096367

Which looks very similar to your spark fun product. It contains a LNA and hence requires 3-5V down the antenna cable to power it. 

If you look at the nRF9160 Thing Plus data sheet, it appears you have a power switch that provides 3.3V power to the antenna. This is connected to the COEX0 pin, that according to the nRF9160 product specification can be used to control an external LNA. (The board I use has the LNA powered all the time)

Nordic Semi recommend a LNA with SAW filter for the GNSS. But in saying this, our practical experience is its not always needed. We have been using the SKY65943-11 with some on-board chip antennas with good results.

FYI, we have trialled the Molex GPS/LTE combo Flexible directly into the nRF9160 (although not recommended by Nordic)
https://www.digikey.com.au/en/products/detail/molex/2133530150/13985296

Its similar to what you have, but has a specific antenna (single band) for 1.575GHz. Without a saw filter, you may be picking up noise on other bands (2.4 to 5GHz)

It works outside and was getting us a fix in approximately 60 seconds when we were testing on Friday. These antenna are designed to stick on I believe a plastic surface and this can effect the antenna's tuning which we can see on a VNA. 

Nordic's example firmware works (samples/nrf9160/gnss), but we have also been using this for testing:
https://github.com/craigpeacock/nRF9160_Examples/tree/main/GPS

before porting to our commercial product.