07-28-2021, 10:27 AM
(This post was last modified: 07-28-2021, 11:26 AM by dsimic.
Edit Reason: Word choice; Specified the AT command
)
A few days ago, one community member complained on the #pinephone IRC channel about having some kind of weird interference on his PinePhone, during a 2G voice call. After some debugging, which included changing the audio-related modem settings through some of the above-listed AT commands (with no success), we came to a conclusion that we need a weird approach: let's make the modem antenna larger. 
With that mod in place, signal strength (as reported by the "AT+CSQ" command) went up from around -100 dBm, which is considered poor, to around -70 dBm, which is considered very good, and no interference was present during a voice call. Thus, I'd suggest that you try something similar, just to verify whether the issues are caused by the network and low signal strength. Of course, improving the modem antenna is nowhere nearly as easy as sticking a randomly shaped piece of aluminum foil to the back cover, but that's all just for the purpose of testing.
The attached picture shows what the "early prototype" looked like.
With that mod in place, signal strength (as reported by the "AT+CSQ" command) went up from around -100 dBm, which is considered poor, to around -70 dBm, which is considered very good, and no interference was present during a voice call. Thus, I'd suggest that you try something similar, just to verify whether the issues are caused by the network and low signal strength. Of course, improving the modem antenna is nowhere nearly as easy as sticking a randomly shaped piece of aluminum foil to the back cover, but that's all just for the purpose of testing.
The attached picture shows what the "early prototype" looked like.
