Get ready to be surprised, because the 800Mhz band used for AMPS (1G / analog cellular) was explicitly carved off as a no-receive zone by Congress because AT&T was pissed[0] anyone could just listen in on any cellphone conversation. I'm told the law actually makes it really difficult to legally sell fully open software-defined radios (SDR), even though nobody uses analog cellular anymore, because you still have to design the SDR to be tamper-proof against attempts to receive 800Mhz.

[0] Wikipedia also mentions the existence of cloning tools that would let you copy any AMPS subscriber ID and program another phone with the same number, stealing the subscriber's account. I suspect AT&T was more angry about that.