PULOX PO-900 Mode D'emploi page 149

For transmitters rated at a maximum output power not listed above,
the recommended separation distance d in metres (m) can be
estimated using the equation applicable to the frequency of the
transmitter, where P is the maximum output power rating of the
transmitter in watts (W) according to the transmitter manufacturer.
NOTE 1 At 80 MHz and 800 MHz, the separation distance for the
higher frequency range applies.
NOTE 2 These guidelines may not apply in all situations.
Electromagnetic propagation is affected by absorption and reflection
from structures, objects and people.