CODAR Ocean Sensors SeaSonde Manual de usuario
User’s Guide for:
SeaSonde®Radial Site
Antenna Site Selection
CODAR OCEAN SENSORS, LTD.
1000 Fremont Ave., Suite 145, Los Altos, CA 94024-6057 USA
Tel. (408) 773-8240 FAX (408) 773-0514
www.codaros.com
e-mail: [email protected]
©2003 Codar Ocean Sensors, Ltd.
Dec 18, 2003
Please read the disclaimer on the last page of this publication.
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This Guide will give you general guidelines for finding a good location for your SeaSonde
Antennas.
This Guide does not cover the electronics of site installation. For information on electronics,
please consult the Radia_Site_Assembly Guide.
Site selection is critical to allow SeaSonde to perform as it was designed.
This Guide contains seven sections:
1. What do the Antennas look like?
2. Antenna “Clear Area.”
3. Distance between Antennas.
4. SeaSonde’s broad coverage area.
5. Desirable locations: general principles.
6. Specific examples of good/bad locations.
7. Summary.
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Section 1: What do the Antennas look like?
You will be selecting sites for two Antennas, which look like this when assembled:
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Section 2: Antenna “Clear Area.”
The area around the Receive Antenna should be kept clear. Especially from metallic objects :
The same principle applies to the Transmit Antenna:
“R” depends on how high the object is, measured from the surface of the ground.
Some examples of obstructions: trees, telephone poles, buildings, storage tanks.
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Use this table to find “R:”
The taller the object, the farther away it should be.
Note that for an object of a given size, the distance to Antennas is a minimum.
The farther away any obstructions are, the better.
Electrically conductive objects are more serious obstructions than non-conductive.
Also,an area below ground should be clear of long, continuous objects that conduct electricity
such as pipes and electric cables:
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Below ground clear area is circular, and has a radius of 100 meters on the surface of the
ground, and a depth of 10 meters below ground.
In some SeaSonde installations, cables leading to the Antennas may be buried. Such cables are
an exception to underground clear area rules.
Electrically conductive objects that have a length of less than 1 meter, and are not continuous,
can be much closer:
Non-conductive objects are of no consequence in underground clear areas.
Underground Clear Area is the same for the Receive Antenna.
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Section 3: Distance between Antennas.
A minimum distance between the Antennas should be observed, to prevent signals from the
Transmitting Antenna from overloading the Receiver:
“l” equals the wavelength at which your SeaSonde operates. Look up your operating frequency
in SeaSonde documentation, and use this table:
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Section 4: SeaSonde’s broad coverage.
Here is how the Transmit Antenna sends radio waves:
The Transmit Antenna sends signals equally in all directions on a horizontal plane.
The Receive Antenna picks up signals in a similar manner, over a broad, flat plane.
Because of SeaSonde’s wide coverage, Antennas can be installed in many places. On oil drilling
platforms or islands, SeaSonde can provide complete coverage of surrounding waters.
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Section 5: Desirable locations: general principles.
Antenna sites are usually located in coastal areas because of proximity to water:
Unfortunately, coastal areas are likely places for lighthouses, piers, or parks. Structures of
any kind may interfere with SeaSonde Antennas. Tourists, beachcombers, or sightseers may
be present, creating the possibility of theft and vandalism.
A point or peninsula at a remote,coastal area is an excellent location for SeaSonde Antennas:
A peninsula location takes best advantage of SeaSonde’s wide coverage and allows the
Antennas to be close to water.
Notice the gentle slope of the land near the water at this desirable location. Flat or gently
sloping land is compatible with SeaSonde’s horizontal pattern.
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Section 6: Specific examples of good/bad locations.
A flat rooftop is often a good Antenna site:
Normally, this building would be a major obstruction for SeaSonde. However, because the
Antennas are mounted on the roof, SeaSonde’s broad, horizontal Antenna patterns are not
blocked.
Notice the lack of obstructions on or near the roof. Water towers, Elevator Shafts, Television
antennas or satellite dishes on the roof, or power lines or tree branches nearby at roof level,
would probably make this site unusable. This location maintains the principle of Above
Ground Clear Area, even though it is elevated above the earth.
Raising Antennas on a 4-meter-high post is usually a good practice for roof mounting.
SeaSonde’s radio signals are partly absorbed by a flat roof, and raising the Antennas from the
roof reduces this effect.
Raising the Antennas above the roof also deals with the problem of Underground Clear Area.
At this location, the rooftop takes the place of the “Ground.”
A major advantage of this location is height above ground, which discourages vandalism.
Another benefit of this site is closeness to water. At this location, the Antennas are about 20
meters from the water.
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