User's Manual Part 2

Instruction manual
107
E04572
13.3 Transmission range
Because VHF signals travel in a straight line and are not reflect-
ed back off the ionosphere as lower frequency signals are, the
range of VHF signals is limited to “line of sight”, beyond
which the other vessel passes behind the curve of the Earth.
Therefore, the range will increase greatly the higher above sea
level the antenna is, as Fig 13.1 illustrates (assuming maximum
transmission power is used).
The typical ship-to-ship range of a fixed VHF radio, such as the
RS82, with a masthead antenna will be approximately 20 km
(12 miles). This will increase as height above sea level increases,
or if the other user’s antenna is at a greater height. Note, that
the range between the yacht with the antenna mounted on a
9m (30ft) mast and the shore station increases to 46–53 km
(29–33 miles).
Fig 13.1 - VHF transmission ranges