One important factor in the distance a two-way radio will communicate is
its power output. This power output is measured in “watts.” You’ve
likely heard an FM radio station say they are broadcasting at 50,000 or
100,000 watts. Well, a handheld business-type two-way radio usually
broadcasts at 1-5 watts. A vehicle mobile radio may broadcast anywhere
from 5 to 100 watts. The more watts a radio has, the farther it can
Why is this? When water moves through a pipe it loses pressure along
the way. When electricity flows along a wire it loses current. When an
object is rolling, it will eventually stop rolling due to friction.
Radio waves operate by the same laws of physics as everything else so
there will be signal loss along the way. But if you apply more water
pressure, more electrical current, or get the rolling object moving
faster, you'll get more distance out of all of them. The same is true
for a radio signal. Increasing the power in watts at the source helps
overcome any "resistance" along the way.
Keep in mind that for battery-powered handheld radios more watts is
not always a good thing. The higher the wattage, the quicker your
batteries run down.