VHF NX2000 English
41
The most popular antenna for marine use are 1m (3ft 3in) long. On sail boats these are
usually mounted at the masthead, where the length of the antenna keeps it clear from
the navigation lights and wind vanes etc. This type of antenna can also be mounted on
the cabin roof or radar arch on powerboats.
Longer whip antenna are recommended for larger boats. These radiate the same total
power as smaller antenna, but concentrate 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 E).
Here the wider beam of the shorter antenna will be more universally effective, although
the signal will be weaker (Fig F):
Therefore vessels with a large heel angle (small sailboats) would do better with a short
masthead antenna. Your local agent should be able to provide specific advice on
antenna choice for the vessel it is to be fitted on.
The antenna coaxial cable and any connectors used must be rated at
50Ω. Under no circumstances should standard domestic TV cable and connectors be
used. Incorrectly rated cabling and connectors could result in power not reaching the
antenna, but also power could be reflected back into the Radio, damaging it in the
process.
Fig F
Fig E
