[ajdhsjakafjt]

Mobile networks are two-way systems. If you have perfect reception of the mobile network - let's say full bars! - then that doesn't mean the mobile network also has reception of your mobile device.

Most of the time, your phone is in RX-only mode to save battery. It listenes for incoming data every millisecond or two, but no more. But as soon as you actively use the network, things change. The basestation must receive your signals as well. This may suddenly and dramatically change the perception of "signal quality". Before it's RX quality only, then it's RX+TX quality.

With incoming or outgoing calls, your phone may switch to another technology. While it may be idling in 4G, large parts of the world rely on 2G for voice calls. As soon as the call starts, the phone switched to 2G and naturally shows 2G reception.

[giancarlostoro]

Interesting, yeah I don't know a whole lot about the underlying tech. I figure Google Maps uses my mobile data which explains why it sorta appears to have lost it's own darn mind.