4.2 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 4.1 illustrates (assuming maximum
transmission power is used):
Therefore, the typical ship to ship range of a fixed VHF radio
such as the RT62/RT64 with a masthead antenna will be
approximately 20 Km (12 miles). This will increase as height
above sea level increases, or if the other radio user’s antenna is
at a greater height - note that the range between the yacht with
the antenna mounted on a 9 M (30 Ft) mast and the shore sta-
tion increases to 46-53 Km (29-33 Miles).
Instruction Manual
25
E04074
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