It's not just the radios, it's the antennas as well, a ~1MHz antenna is very different to a ~100MHz antenna.

Gosh if only there was some sort of widely distributed network with transmitters all over the place that could get information to portable devices that people carried with them at all times and which can be woken up remotely even if they're otherwise asleep/turned off, we wouldn't need to push this obsolete century-old technology with a vague justification of "emergencies".