I didn’t talk much about 900Mhz / 1.2 Ghz since we cant use those here in the UK and most of eurpe as they are reserved for other applications and not open to the public But the best way to get better signal is to use high gain antennas on the ground, check out or FPV antenna guide for more info. Also if you plan to fly over a city make sure you get proper permission as its kind of illegal in most countries nowadays.