insulated {especially where passing through the deckhead/bulkhead} and
must be kept clear of metal stanchions, handrails or other metal parts.
Your equipment user manual will tell you what length of antenna
can be used with your own antenna coupler {e.g. not less than seven
metres and not more than 15 metres}. As a rule, the closer you can get
your transmit antenna to the longer length allowed, the better will be
the performance on the lower marine bands.
Antenna maintenance and checks
Radio-frequency burns {caused by touching an antenna during
transmission} are very painful and tend to stay that way for days. Burns,
and even mild electric shocks, can cause a person to step backwards off
the monkey island. Although the burn/shock may not be fatal, falling to
the deck below will probably result in injury or death. Before working
on antennas you should:
- Switch-off all radio, satcom and radar equipment if it is safe to do so.
- Remove the main DC supply fuse if accessible, to prevent inadvertent
use of radio and other equipment.
- Move the SSB antenna earth switch to the position that will disconnect
the SSB radio from the antenna; connect the SSB to the dummy load
and discharge any static electricity from the antenna itself.
Put a sign on the SSB radio advising others that someone is working aloft.
You can then send someone up to check antennas, connections and
insulators. Insulators must be kept clean {free of salt and carbon deposits}
or your transmitter energy will carve a track across the insulator to the
metal superstructure rather than be radiated into free space {the surrounding
atmosphere}. Clean with fresh water {salt water will leave a layer of new
salt on the insulator}. Connections must be tight and not corroded, nor
burned {loose connections will cause arcing when transmitter energy is
passing through the connection}. ArCing will present a high-resistance path
to your transmitter, lowering the performance of the equipment. Wire
antennas and lead-in should be clear of metal superstructure, guardrails
and stanchions - and should not be frayed. The weak link should be intact.
A weak link may be provided on longer wire antennas, between the
insulator and the mast, to control where any break will occur if too much
pressure is put on the antenna {e.g. when masts flex during heavy
weather}. The weak link is made of thinner wire than the main antenna.
The safety loop is made of the same gauge wire as the antenna itself and
will prevent the whole antenna falling to deck if the weak link breaks.
148 THE NAUTICAL INSTITUTE
