Instruction Manual
41
E03912 Issue 2.0
The most popular antennas for marine use are 1 m (3 ft 3 in)
long. On sailboats these are usually mounted on the masthead,
where the length of the antenna keeps it clear from the naviga-
tion lights and windvanes, etc. This type of antenna can also be
mounted on the cockpit roof or garage of power boats.
Longer whip antennas are recommended for larger boats – these
radiate the same total power as smaller antennas, but concen-
trate it into a narrower beam, which is advantageous on a tall
mast at extreme range where concentrating the available power
into a narrow horizontal beam becomes more important.
However, if the antenna is not vertical when transmitting, the
beam will be angled either too high or too low (Fig 4.6).
Fig 4.7 - Effect of heel on range of 1 m marine antennas
Fig 4.6 - Effect of heel on range of longer whip antennas
Here the wider beam of the shorter antenna will be more uni-
versally effective, although the signal will be weaker (Fig 4.7).
Therefore, for vessels with a large heel angle (small sailboats) a
short masthead antenna would be a better choice. Your local
agent should be able to provide specific advice on antenna
choice for the vessel it is to be fitted to.
WARNING The antenna coaxial cable and any connectors
used must be rated at 50 Ω. Under no circum-
stances should standard domestic TV cable and
connectors be used. Incorrectly rated cabling and
connectors could result in power not reaching the
antenna, but power could also be reflected back
into the radio, damaging it in the process.
