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Subel. P
6 questions
Subelement P
Satellite
Section 96
INMARSAT Communications Systems-1
What is the orbital altitude of INMARSAT Satellites?
  • 16, 436 miles.
  • Correct Answer
    22,177 miles.
  • 10, 450 miles.
  • 26,435 miles.

What is the orbital altitude of INMARSAT Satellites?

22,177 miles.

From mattd2414:

The Inmarsat satellite constellation consists of 13 satellites in a geosynchronous (GEO) orbit approximately 22,177 miles above the earth.

Though Inmarsat website reports 22,236 miles, this is not reflected on the exam and the answer choice 22177 will be graded as being correct

Please see Global site for article on Different Types of Satellite Orbits

In the Geostationary orbits, satellites hover about 35,790 kilometers above Earth. This is 22,238.875 miles.

For more info, please see Wikipedia's article on Inmarsat

Also, see the Inmarsat own site for more info.

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Which of the following describes the INMARSAT Satellite system?
  • AOR at 35° W, POR-E at 165° W, POR-W at 155° E and IOR at 56.5° E.
  • AOR-E at 25° W, AOR-W at 85° W, POR at 175° W and IOR at 56.5° E.
  • Correct Answer
    AOR-E at 15.5° W, AOR-W at 54° W, POR at 178° E and IOR at 64.5° E.
  • AOR at 40° W, POR at 178° W, IOR-E at 109° E and IOR-W at 46° E.

Which of the following describes the INMARSAT Satellite system?

  • AOR-E at 15.5° W,
  • AOR-W at 54° W,
  • POR at 178° E and
  • IOR at 64.5° E.

For INMARSAT from Satphonecity site, article on Inmarsat Coverage:

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What are the directional characteristics of the INMARSAT-C SES antenna?
  • Highly directional parabolic antenna requiring stabilization.
  • Wide beam width in a cardioid pattern off the front of the antenna.
  • Very narrow beam width straight-up from the top of the antenna.
  • Correct Answer
    Omnidirectional.

What are the directional characteristics of the INMARSAT-C SES antenna?

Omnidirectional.

For more information, please see Inmarsat site for pdf document called INMARSAT MARITIME DESIGN & INSTALLATION GUIDELINES (DIGS), DIGS ISSUE 7, 28.05.2020, section B.21, where the omnidirectional antenna is specified.

Also, see an example and technical specifications for a Inmarsat-C MOBILE EARTH STATION, on Furuno USA site.

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When engaging in voice communications via an INMARSAT-B terminal, what techniques are used?
  • Correct Answer
    CODECs are used to digitize the voice signal.
  • Noise-blanking must be selected by the operator.
  • The voice signal must be compressed to fit into the allowed bandwidth.
  • The voice signal will be expanded at the receiving terminal.

When engaging in voice communications via an INMARSAT-B terminal, what techniques are used?

CODECs are used to digitize the voice signal.

CODEC codes analog voice or any other audio into digital, and decodes it back to analog so that it is understood by humans.

For more information, please see Sonary site, for the article on What Is a Codec And Why Is It Important For VoIP?

Also, see Crypto Museum site, for the article CODEC Coder-decoder

The Analog IC Tips site, article What is a CODEC? provides an solid overview of this set of rules for audio transformations.

See Wikipedia's article Pulse-code modulation for solid overview.

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Which of the following statements concerning INMARSAT geostationary satellites is true?
  • They are in a polar orbit, in order to provide true global coverage.
  • They are in an equatorial orbit, in order to provide true global coverage.
  • Correct Answer
    They provide coverage to vessels in nearly all of the world’s navigable waters.
  • Vessels sailing in equatorial waters are able to use only one satellite, whereas other vessels are able to choose between at least two satellites.

Which of the following statements concerning INMARSAT geostationary satellites is true?

They provide coverage to vessels in nearly all of the world’s navigable waters.

From kb9lth:
Geostationary satellites are stationary and do not orbit. The two answers that talk about orbit are not correct.

Please see Global site for article on Different Types of Satellite Orbits

In the Geostationary orbits, satellites hover about 35,790 kilometers above Earth. This is 22,238.875 miles.

For more info, please see Wikipedia's article on Inmarsat

Also, see the Inmarsat own site for more info.

Last edited by markadlerdallas. Register to edit

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Which of the following conditions can render INMARSAT -B communications impossible?
  • An obstruction, such as a mast, causing disruption of the signal between the satellite and the SES antenna when the vessel is steering a certain course.
  • A satellite whose signal is on a low elevation, below the horizon.
  • Travel beyond the effective radius of the satellite.
  • Correct Answer
    All of these.

Which of the following conditions can render INMARSAT -B communications impossible?

All of these.

  • (A).   An obstruction, such as a mast, causing disruption of the signal between the satellite and the SES antenna when the vessel is steering a certain course.

  • (B).   A satellite whose signal is on a low elevation, below the horizon.

  • (C).   Travel beyond the effective radius of the satellite.

These conditions may affect any radio transmission or receiving.

Inmarsat has a support site at Inmarsat Support

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