What causes the SART to begin a transmission?

After being activated the SART responds to RADAR interrogation.

From Element 1, Question 22D4 SART:
"This is a 9 GHz transponder capable of being received by vessel’s X-band navigational RADAR system."

SART operates in the 9.2 to 9.5 GHz frequency band, which is the Super High Frequency (SHF). The SHF band extends from the 3 GHz to 30 GHz, with wavelength from 1 to 10 centimeters.

This frequency range is known as the microwave range, often referred to as the X wave range.

Because the wavelength is just few centimeters (3 cm), this narrow radio beam works well with horn and parabolic (microwave dishes) antennas, which facilitates line-of-sight transmissions, somewhat like the VHF band waves.

If you position the SHF antenna as high as possible, the propagation range will increase with height.

For a great illustrated info, see The Royal National Lifeboat Institution's article on SARTS, (Search and Rescue Radar Transponders)

For more info, see Wikipedia's articles on Search and rescue transponder and Super high frequency.

Good overview is on Blue Seas site article, SART - Search and Rescue Transponder.

An important reference is provided by the International Telecommunications Union (ITU) in the RECOMMENDATION ITU-R M.628-3, entitled TECHNICAL CHARACTERISTICS FOR SEARCH AND RESCUE RADAR TRANSPONDERS, (see Point 1)

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How should the signal from a Search And Rescue RADAR Transponder appear on a RADAR display?

A series of 12 equally spaced dots.

A SART, when interrogated by a 9GHz X-band radar, will sweep rapidly (0.4 μS) through the band once and then back slowly (7.5 μS).

This will happen 12 times, with each producing a "dot" as the frequency will match that of the radar, thus producing a line of 12 dots.

For a great illustrated info, see The Royal National Lifeboat Institution's article on SARTS, (Search and Rescue Radar Transponders)

For more info and radar display, please see Wikipedia's article on Search and rescue transponder

To see full screen radar display, please see Wikipedia's SART Radar Display

For active radar view, see Japan Radio Co. Ltd's article on SART(SEARCH AND RESCUE RADAR TRANSPONDER) JQX-30A

Highly recommended is the pdf user manual for SART, to get realistic details, for McMurdo's S4 Rescue SART Search and Rescue Transponder.

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In which frequency band does a search and rescue transponder operate?

9 GHz

The Search and Rescue Transponder (SART) functions only on the 3 centimeter wavelength, which is the 9 GHz X-band.

For more information, please see Wikipedia's article on Search and rescue transponder

Also, see Marine Insight article What is Search and Rescue Transponder (SART)?

SART operates in the 9.2 to 9.5 GHz frequency band, which is the Super High Frequency (SHF). The SHF band extends from the 3 GHz to 30 GHz, with wavelength from 1 to 10 centimeters.

This frequency range is known as the microwave range, often referred to as the X wave range.

Because the wavelength is just few centimeters, this narrow radio beam works well with horn and parabolic (microwave dishes) antennas, which facilitates line-of-sight transmissions, somewhat like the VHF band waves.

If you position the SHF antenna as high as possible, the propagation range will increase with height.

For a great illustrated info, see The Royal National Lifeboat Institution's article on SARTS, (Search and Rescue Radar Transponders)

For more info, see Wikipedia's articles on Search and rescue transponder and Super high frequency.

Good overview is on Blue Seas site article, SART - Search and Rescue Transponder.

An important reference is provided by the International Telecommunications Union (ITU) in the RECOMMENDATION ITU-R M.628-3, entitled TECHNICAL CHARACTERISTICS FOR SEARCH AND RESCUE RADAR TRANSPONDERS,

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Which piece of required GMDSS equipment is the primary source of transmitting locating signals?

An EPIRB transmitting on 406 MHz.

From Element 1, Question 21D6:
Advantages of a 406 MHz satellite EPIRB include:

• It is compatible with the COSPAS-SARSAT Satellites and Global Maritime Distress Safety System (GMDSS) regulations.

• Provides a fast, accurate method for the Coast Guard to locating and rescuing persons in distress.

• Includes a digitally encoded message containing the ship’s identity and nationality.

The 406 MHz satellite EPIRB provides global coverage, using low orbit polar-position satellites, under 406 MHz beacon. The coverage may not be immediate when EPIRB beacon is transmitted.

The signal carries the GPS coordinates which provide fast location data. The GEOSAR group of satellites facilitates the communication of location data. They include geostationary orbiting satellites, Indian national satellite, and the Metosat satellite. See SARSAT Search and Rescue Satellite-Aided Tracking site for the Search and Rescue Satellites.

This system accepted internationally as a radiocommunication service to respond in distress situations once the location is determined whether for ships or planes.

Please see the Code of Federal Regulations, Title 47, Chapter I, Subchapter D, Part 80, Subpart W - Global Maritime Distress and Safety Systems (GMDSS), and especially § 80.1077 Frequencies.

For more info, please see the US Coast Guard article on EMERGENCY POSITION INDICATING RADIO BEACON (EPIRB)

Also, please see the Sea of Solutions site for the article on What is an EPIRB?

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Which of the following statements concerning satellite EPIRBs is true?

Once activated, these EPIRBs transmit a signal for use in identifying the vessel and for determining the position of the beacon.

An EPIRB (Emergency Position Indicating Radio Beacon) transmits on 406 MHz. It facilitates voice transmissions to ensure that the unit was not activated accidentally.

For overview of EPIRB system, please see Boat US Foundation article How EPIRBs Work

For more info, see Marine Insight's site for an article on What is An Emergency Position Indicating Radio Beacon (EPIRB)?

And, also see Search and Rescue Satellite Aided Tracking

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What statement is true regarding 406 MHz EPIRB transmissions?

Transmits a unique hexadecimal identification number.

Called the Unique ID#, or HexID, the hexadecimal ID number, (15 hex characters) a unique code, is present in transmission of distress beacons, when the EPIRB is activated. Also, the location data from GPS may be transmitted.

For more information, please see 406 Registration site, for the article What is a Hex ID, and where can I find mine?

Also, please see an excellent PowerPoint presentation from US Coast Guard, called EPIRB’s How They Work & DF-430 On the C-130H

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