Antenna Installation Recommendations - Simrad RT62 Instruction Manual

RT62 & RT64

3.3 Antenna Installation Recommendations

Fig 3.5 - Effect of heel on range of
1m marine antenna
Fig 3.6 - Effect of heel on range of
longer whip antenna
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storage or security, so leave an adequate length of cable to ease
disconnection. The flying lead from the rear of the radio can
then be plugged into the power supply lead. Note that the
configuration of the plug prevents incorrect connection.
The antenna is connected to the radio using a standard PL259
type connector as fitted to most marine antennae. If fitting to
an existing antenna, check that the contacts are not corroded
before connecting, as this will affect the quality of the signal.
Ensure that the retaining collar of the antenna plug is securely
tightened to prevent accidental disconnection.
The extension speaker socket takes a standard 3.5mm jack plug.
The speaker used must have a minimum impedance of 8Ω.
The most important factor in the performance of the radio will
be the quality and positioning of the antenna. Most recorded
problems with VHF radios are related to poor antenna siting,
faulty cabling, poor quality cable joints and low voltage supply.
Even a VHF as highly advanced as the RT62/RT64 cannot com-
pensate for these factors. Therefore, if replacing an existing
VHF installation, it is important that these factors are checked
when installing the radio.
As the range of VHF signals are governed by line of sight (see
section 4.2), the antenna should be placed as high as possible,
while remaining clear of any metallic objects that could influ-
ence the resonance of the antenna.
The most popular antennae for marine use are 1m (3ft 3in)
long. On sail boats these are usually mounted on the mast-
head, where the length of the antenna keeps it clear from the
navigation lights and windvanes etc. This type of antenna can
also be mounted on the cockpit roof or garage of power boats.
Longer whip antennae are recommended for larger boats.
These radiate the same total power as smaller antennae, 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 3.6). Here
the wider beam of the shorter antenna will be more universally
effective, although the signal will be weaker (Fig 3.5).
Therefore vessels with a large heel angle (small sailboats)
would be better choosing a short masthead antenna. Your local
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