No Connection to Carrier from Pinephone 3G Model

[nonoreply]

Hi there! I have copied the title of the thread (link below) started by @merlin - as its content gives nearly an exact match.
https://forum.pine64.org/showthread.php?tid=11649

My phone's modem does not register to a carrier/provider anymore, after doing so successfully for about 9 months.

I've tested
- on several distributions consecutively flashed to eMMC (manjaro, mobian, arch)
- with two sim cards of different providers/carriers (working fine in other mobile phones)

While @merlin stated in his solution 'The connector was lying next to the plug' (referring to an antenna issue),
I could not see any lose cable or connector after removing the midframe. Which antenna, anyway? The one for Wlan?
I thought the modem's cellbroadcast related antennas are integrated into the midframe as a coating. Any suggestions?

[nonoreply]

After I had removed and reinserted the midframe and after the preventive resetting of the U.FL antenna connection, the phone was able to establish a relatively stable internet connection (LTE, less than 35% Signal Strength) for about 30 minutes (but no calls). After that, I have flashed the phone's eMMC from Mobian back to Manjaro/Phosh. Still no calls + highly erratic registration to carrier/provider/cell tower.

So far so bad ... it is really unsatisfying. I am not able to track down the real cause of the modem related issues. Does anyone have an idea how to distinguish between bad/broken modem or bad/broken signal reception (antenna)?

[wibble]

You could try an alternate antenna - it shouldn't be too hard to track down a 4G antenna with the right connector.

As far as the modem goes, you're pretty much limited to what error reporting it might provide. You would have to check the AT command manual to see what's documented. I'm also not sure what ModemManager or oFono do with any errors reported - more docs or code to read. You could disable ModemManager or oFono and watch what happens with a serial terminal instead, in case they're silently dropping error messages.

Another possibility is a change in local radio infrastructure - the companies change their equipment from time to time, and failures do occur. Unless you kept a record of the details from when it was working before this will be a hard one to rule out.