What PMR446 is
PMR446 is a licence-free service on 446.0 to 446.2 MHz, available in Europe and in several other countries. Analogue radios are limited to 500 mW effective radiated power, and the European rules require an integral antenna, although national rules can differ, so check yours. At 0.5 W with an antenna close to 0 dBi, the signal is a small fraction of what an amateur handheld produces.
Realistic range
In a city the usual range is a few hundred metres or less; on flat open country it is a few kilometres, and it can be much longer from high ground with a clear line of sight. Woods and buildings shorten it. Held at 1.5 m the horizon on flat ground is about 5 km per radio, so two people on a flat field cannot go much beyond 10 km even in perfect conditions.
Height is your best upgrade: standing on a hill or a roof can multiply the range several times, while a free-space calculation at 446 MHz gives only 105 dB of loss over 10 km, easily absorbed by a hill in the path.
Estimate it before you go
Place one radio on the coverage map, choose 446 MHz and the FM or DMR mode, set 0.5 W and a handheld antenna, and read the area that stays green. The radio horizon calculator gives the upper limit for any pair of heights.
