(08-16-2020, 02:11 PM)wibble Wrote: Last time I looked in this detail was with 2G which was much simpler, so I may be mistaken with what follows...I hope someone with more understanding will correct me!

If bands 2 and 4 have sufficient signal it should use them so long as they haven't been disabled. It won't 'see' band 66 at all. You may have seen the list of supported and currently enabled bands in the 'mmcli -m 0' output - I usually get it, but occasionally it doesn't show for reasons I don't understand. In my case both lists are the same, so all supported bands are enabled - I assume this is the default as I haven't done anything to change it. Mave a look at the mmcli man page and the ModemManager documentation to see what it can do - the --set-allowed-modes=[list of modes] option seems like the one if you need it. It doesn't seem to provide the level of information I remember from 2G, but that may be down to ModemManager rather than what the modem can provide. UBPorts (and plasma-mobile?) use oFono which is functionally similar but accessed slightly differently, and might help diagnosing. It's also possible to shut down ModemManager and access the modem's serial port with a serial terminal like picocom. This will allow you to run the AT commands directly, ruling out any issues with ModemManager or oFono hiding things or not working correctly, but this will require some reading of the Quectel AT command documentation.

It may be that there's some specific issue with US T-Mobile for the modem, ModemManager or oFono - this is where a detailed list of what has worked with which mobile networks would be useful. it could also be a problem with the modem firmware (possible but I think unlikely) or even an assembly issue that means the antenna isn't connecting properly.

(08-16-2020, 05:29 AM)FOSSagent0 Wrote: @wibble Your advice was helpful, I was able to see that it was band issue. On my Android phone I used LTE Discovery app and saw that most of the time my phone was connecting to band 2. But it did show that it was connecting for a little bit to band 66 which is not supported by the Quecetel EG-25g modem.

Is there a way to keep the Pinephone from trying to connect to band 66? Not sure how accurate LTE discovery is but it shows other bands in my area which are 2 and 4.