CODAR Ocean Sensors SeaSonde User manual

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. [phone] FAX [phone]
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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Here is another good site:
This is a good place for SeaSonde antennas because it is close to water, on flat land and has a
clear, unobstructed view of the water.
Another advantage of this site is closeness to water. At this site, Antennas are no more than
thirty meters from water.
While this site is excellent from the perspective of Antenna patterns, it does show signs of being
accessible to the public. Note the well-worn footpath near the Antennas.
A cliff or bluff is a good location:
Near the top edge of a bluff or cliff is a good place if the distance to water is not too great.
Notice the lack of obstructions such as buildings near this site, and the remoteness of this
location. The cliff is not an obstruction because it is below the Antennas.
The land behind the cliff is reasonably flat. Clear Area can be easily maintained around the
antennas. Distance to water is a straight line from the antenna to water.
The closer Antennas are to water, the better.

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What is the maximum distance to the water for Antenna sites? That depends on frequency of
operation, which is listed in SeaSonde documentation. Use this table:
Here is a poor Antenna site:
At the above location, SeaSonde antennas would be mounted on a bluff more than 250 meters
from the water. That is too far, at any operating frequency.
SeaSonde. Radio waves are absorbed much more by land than by water.
This would be a good location, except for distance to water. It is on a bluff, well above a
publicly accessible area.

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Here is another poor Antenna site:
Placing antennas near the bottom of a steep hill interferes with SeaSonde operation because
the hillside acts as a reflector. This causes a major distortion of the SeaSonde Antenna patterns.
The top of the hill would be better because the hillside would then be below the flat, horizontal,
patterns of the Antennas.
Remember that a Clear Area must be maintained around Antennas, depending on an
obstruction’s height. This principle would apply to the hillside pictured.
The above location also has the drawback that it is accessible to the public. Notice two passers-
by in the photo.

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Consider this site:
Can you find the problems with this location?
There are several problems. A metal railing is nearby. Buildings are located between the
Antenna site and the water. A large rock also acts as an obstruction.
Also, there is a radio antenna nearby, on top of the building next to the lighthouse. Radio
antennas of any kind (other than SeaSonde) must not be within the Clear Area.
Large, powerful transmitting antennas may cause problems even if they are outside the Clear
Area, especially if they transmit at a frequency near the operating frequency of your SeaSonde.
Remember, Clear Area is a minimum requirement.
Power lines should be avoided:
Electric power lines are major sources of radio interference, and should not be within 100
meters of SeaSonde Antennas.
This location is especially bad because the power lines carry high voltage. Generally, the higher
power lines are from the ground, the higher the voltage they carry. This increases the
likelihood they will be interference sources.

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A fence or railing between the Antennas and water is to be avoided. And, the Antennas pictured
are too close together:
This location may be acceptable, if the Antennas could be raised above the fence by at least
three meters. The Antennas should be separated more.
This photo contains four bad site characteristics. Can you find them?
They are: radio towers, power lines, a fence and large metal objects (shipping containers).

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Section 7: Summary.
Here are some good and bad site characteristics:
Good: Clear Area maintained, flat or gently sloping land, near water, top of a cliff or
bluff, no obstructions nearby, remote, inaccessible to the public.
Bad: obstructions nearby, power lines, antennas (other than SeaSonde), bottom of a cliff,
fence or railing between antennas and water, far from water, accessible to the public.
If you are still not sure where to place your SeaSonde Antennas after reading this Guide, please
contact Codar Ocean Sensors for assistance.
In difficult cases, the final decision about where to place Antennas may have to be made by
technical staff at Codar Ocean Sensors.

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Section 8: Disclaimer.
Copyright:
This publication is copyrighted with all rights reserved by Codar Ocean Sensors, Ltd.
(COS). Pursuant to the United States copyright laws, this publication may not be copied or
otherwise reproduced, in whole or in part, without prior written consent of COS, except for the
private, internal use of COS customers. Any permitted copies must include the same proprietary
and copyright notices as were affixed to the original. Copying includes translating into another
language.
Trademarks:
The designations SeaSonde and WaveSonde are trademarks registered by Codar Oceans Sensors,
Ltd with the United States Patent and Trademark Office, Washington, D.C.
Waiver of Legal Responsibility:
Although COS has made every effort to ensure the accuracy and completeness of the information
contained in this publication, neither COS nor its contractors make any warranty or
representation, either expressed or implied, with respect to this publication, as to its quality,
performance, merchantability, or fitness for a particular purpose. This publication is provided
strictly "as is." You, the user, are assuming the entire risk as to the quality and performance of
the information contained in this publication.
In no event will COS be liable for any direct, indirect, special, incidental, or consequential
damages arising from the use of the information contained in this publication, even if advised of
the possibility of such damages.
Right of Revision:
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