Things that have a bad effect on range:
Obstacles such as buildings, trees, hills, heavy rain, tunnels, low battery etc.
Things that have a good effect on range:
A clear path between radios, height above obstacles, fully charged battery etc.
Other factors affecting range:
Range can be doubled by using a base repeater station, placed in the centre of the required service area. Range can be seriously affected by using the wrong antenna on the radio, see our information section on antennas to enable you to select the best antenna for your radio.