144
their operational life), buoys are repainted with anti-fouling paint and new wire rope
and chain-and-tackle, incorporating in-line steel instrument cages, is prepared and
attached. Following instrument installation, and verification of instrument and communications system performance, the buoy system is ready for redeployment in
days to weeks.
Specialized moorings such as wave buoys and the MapCO2 design may use twopoint moorings incorporating elastic elements in the mooring design in addition to
the normal chain, steel rope, or synthetic fiber cable (see Fig. 3.4). Tensioning
equipment is required for these operations in order to pre-set tension of the elastic
mooring. The MapCO2 mooring, designed for fore-reef deployment on a coral reef
in a region of low tidal amplitude specifies a fully tensioned mooring. The wave
buoy for insular shelf deployment may specify a tensioned elastic mooring and a
second inelastic mooring incorporating a double catenary design to allow for buoy
heave.
8.3.2 High Frequency Radar Deployment and Maintenance
High frequency (HF) radar antennae are deployed as close to the land-sea interface
as practicable to maximize seawater conductivity for signal transmission. For older
units equipped with separate Tx and Rx antennae care must be taken to allow minimum separation between the antenna pair as per manufacturer specifications.
Excessive length of cable runs to electronic control equipment will also impair performance. A few loops of the cable about one foot in diameter are normally turned
and affixed to the antennae to reduce radio frequency interference. Clamp-on ferromagnetic filters may also be affixed to the cable at the console bulkhead fitting to
further reduce interference. Temporary antenna emplacements require only a simple
base (a parasol base placed upon a plywood sheet will suffice) and stabilizing guy
wires affixed to stakes. More permanent emplacements usually feature a concrete
base with a fabricated aluminum swivel-type antenna base mounted on J-bolts
embedded in the concrete base to simplify lowering of the antenna for servicing
(Fig 8.3).
Antennae Tx and Rx control modules and computer interface must be contained
in low-humidity climate controlled housing either within previously constructed
buildings or in commercial outdoor instrument housing units. These shelters are
furnished with adjustable shelving and air conditioning. GPS antennae for system
synchronization may be mounted atop the housing. Internet connectivity for data
transmission may be wired, through cellular network connection, directional microwave or satellite communication systems.
Normally, HF radar equipment requires little maintenance since there are no
moving parts to wear. Nevertheless, connector corrosion in the nearshore environment may require periodic cleaning or replacement of bulkhead and in-line connectors. Guy wires supporting antennae upright in provisional deployments may sag
and should be checked regularly. It is prudent to dismount and store the antennae
8 Planning, Implementation, and Operation of Coastal Ocean Observing Systems
their operational life), buoys are repainted with anti-fouling paint and new wire rope
and chain-and-tackle, incorporating in-line steel instrument cages, is prepared and
attached. Following instrument installation, and verification of instrument and communications system performance, the buoy system is ready for redeployment in
days to weeks.
Specialized moorings such as wave buoys and the MapCO2 design may use twopoint moorings incorporating elastic elements in the mooring design in addition to
the normal chain, steel rope, or synthetic fiber cable (see Fig. 3.4). Tensioning
equipment is required for these operations in order to pre-set tension of the elastic
mooring. The MapCO2 mooring, designed for fore-reef deployment on a coral reef
in a region of low tidal amplitude specifies a fully tensioned mooring. The wave
buoy for insular shelf deployment may specify a tensioned elastic mooring and a
second inelastic mooring incorporating a double catenary design to allow for buoy
heave.
8.3.2 High Frequency Radar Deployment and Maintenance
High frequency (HF) radar antennae are deployed as close to the land-sea interface
as practicable to maximize seawater conductivity for signal transmission. For older
units equipped with separate Tx and Rx antennae care must be taken to allow minimum separation between the antenna pair as per manufacturer specifications.
Excessive length of cable runs to electronic control equipment will also impair performance. A few loops of the cable about one foot in diameter are normally turned
and affixed to the antennae to reduce radio frequency interference. Clamp-on ferromagnetic filters may also be affixed to the cable at the console bulkhead fitting to
further reduce interference. Temporary antenna emplacements require only a simple
base (a parasol base placed upon a plywood sheet will suffice) and stabilizing guy
wires affixed to stakes. More permanent emplacements usually feature a concrete
base with a fabricated aluminum swivel-type antenna base mounted on J-bolts
embedded in the concrete base to simplify lowering of the antenna for servicing
(Fig 8.3).
Antennae Tx and Rx control modules and computer interface must be contained
in low-humidity climate controlled housing either within previously constructed
buildings or in commercial outdoor instrument housing units. These shelters are
furnished with adjustable shelving and air conditioning. GPS antennae for system
synchronization may be mounted atop the housing. Internet connectivity for data
transmission may be wired, through cellular network connection, directional microwave or satellite communication systems.
Normally, HF radar equipment requires little maintenance since there are no
moving parts to wear. Nevertheless, connector corrosion in the nearshore environment may require periodic cleaning or replacement of bulkhead and in-line connectors. Guy wires supporting antennae upright in provisional deployments may sag
and should be checked regularly. It is prudent to dismount and store the antennae
8 Planning, Implementation, and Operation of Coastal Ocean Observing Systems