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Subelement D
Other Equipment
Section 19
Antennas
What are the antenna requirements of a VHF telephony coast, maritime utility or ship station?
  • Correct Answer
    The shore or on-board antenna must be vertically polarized.
  • The antenna array must be type-accepted for 30-200 MHz operation by the FCC.
  • The horizontally-polarized antenna must be positioned so as not to cause excessive interference to other stations.
  • The antenna must be capable of being energized by an output in excess of 100 watts.

What are the antenna requirements of a VHF telephony coast, maritime utility or ship station?

(A). The shore or on-board antenna must be vertically polarized.

The Very High Frequency (VHF) range is 30 MHz to 299 MHz.

Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart
C - Operating Requirements and Procedures

§ 80.72 Antenna requirements for coast stations.

All emissions of a coast station a marine-utility station operated on shore using telephony within the frequency band 30-200 MHz must be vertically polarized.

§ 80.81 Antenna requirements for ship stations.

All telephony emissions of a ship station or a marine utility station on board ship within the frequency band 30-200 MHz must be vertically polarized.

For info on antenna polarization, especially vertical, please see Electronicnotes site article on Antenna Polarization

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What is the antenna requirement of a radiotelephone installation aboard a passenger vessel?
  • The antenna must be located a minimum of 15 meters from the radiotelegraph antenna.
  • Correct Answer
    The antenna must be vertically polarized and as non-directional and efficient as is practicable for the transmission and reception of ground waves over seawater.
  • An emergency reserve antenna system must be provided for communications on 156.800 MHz.
  • All antennas must be tested and the operational results logged at least once during each voyage.

What is the antenna requirement of a radiotelephone installation aboard a passenger vessel?

(B). The antenna must be vertically polarized and as non-directional and efficient as is practicable for the transmission and reception of ground waves over seawater.

Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart
S - Compulsory Radiotelephone Installations for Small Passenger Boat

§ 80.905 Vessel radio equipment.

47 CFR 80.905(d) A VHF-DSC radiotelephone installation or a remote unit must be located at each steering station except those auxiliary steering stations which are used only during brief periods for docking or for close-in maneuvering.

A single portable VHF-DSC radiotelephone set meets the requirements of this paragraph if adequate permanent mounting arrangements with suitable power provision and antenna feed are installed at each operator steering station.

Additionally, for vessels of more than 100 gross tons, the radiotelephone installation must be located at the level of the main wheelhouse or at least one deck above the vessel's main deck.

§ 80.913 Radiotelephone receivers.

47 CFR 80.913(a) If a medium frequency radiotelephone installation is provided, the receiver must be capable of effective reception of J3E emissions, be connected to the antenna system specified by § 80.923, and be preset to, and capable of accurate and convenient selection of, the frequencies 2182 kHz, 2638 kHz, and the receiving frequency(s) of public coast stations serving the area in which the vessel is navigated.

47 CFR 80.913(c) If a very high frequency radiotelephone installation is provided, the receiver used for maintaining the watch required by § 80.303 must be capable of effective reception of G3E emission, be connected to the antenna system specified by § 80.923 and be preset to, and capable of selection of, the frequencies 156.300 MHz, 156.800 MHz, and the receiving frequency(s) of public coast stations serving the area in which the vessel is navigated.

§ 80.923 Antenna system. An antenna must be provided in accordance with the applicable requirements of § 80.81 of this part which is as efficient as practicable for the transmission and reception of radio waves. The construction and installation of this antenna must insure proper emergency operation.


Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart C Station Requirements - Ship Stations

§ 80.81 Antenna requirements for ship stations.

All telephony emissions of a ship station or a marine utility station on board ship within the frequency band 30-200 MHz must be vertically polarized.

For info on antenna polarization, especially vertical, please see Electronicnotes site article on Antenna Polarization

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What is the most common type of antenna for GMDSS VHF?
  • Horizontally polarized circular antenna.
  • Long wire antenna.
  • Both of the above.
  • Correct Answer
    None of the above.

What is the most common type of antenna for GMDSS VHF?

(D). None of the above.

The most common type of GMDSS VHF antenna is a vertical whip.

Please see for details, Antennaexperts site article "HF VHF UHF GMDSS Antennas"

Longwire antennas are normally used for HF.

VHF communications are normally vertically polarized so horizontally-polarized antennas should not be used.

For more info, please see Wikipedia's article on Antenna types

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What is the purpose of the antenna tuner?
  • Correct Answer
    It alters the electrical characteristics of the antenna to match the frequency in use.
  • It physically alters the length of the antenna to match the frequency in use.
  • It makes the antenna look like a half-wave antenna at the frequency in use.
  • None of the above.

What is the purpose of the antenna tuner?

(A). It alters the electrical characteristics of the antenna to match the frequency in use.

If the impedance (think like resistance in Ohms) for the transmitter is different than for the antenna, then it will not optimize effective radiating power.

If the Ohms of the antenna are higher, than some power is reflected back to the transmitter, and the transmitter will adjust. The tuner makes the transmitter think that the Ohms match, so it sends full power.

This is key component in the transmission process. For more info, please see wcares.org's pdf presentation HOW DOES AN ANTENNA TUNER WORK?

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What advantage does a vertical whip have over a long wire?
  • It radiates more signal fore and aft.
  • Correct Answer
    It radiates equally well in all directions.
  • It radiates a strong signal vertically.
  • None of the above.

What advantage does a vertical whip have over a long wire?

(B). It radiates equally well in all directions.

Vertical whips are relatively non directional, and radiate well in all directions.

If antenna is sloped from vertical position, then it acquires a radiation pattern (or shape). This affects the antenna radiation efficiency. This means, it does not transmit equally in all directions.

In wire, the radiation power travels to the end of the wire, and does not provide radiation in all directions.

For great illustration of patterns, see Wikipedia article on Omnidirectional antenna

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A vertical whip antenna has a radiation pattern best described by?
  • A figure eight.
  • A cardioid.
  • Correct Answer
    A circle.
  • An ellipse.

A vertical whip antenna has a radiation pattern best described by?

(C). A circle.

Vertical whip antennas usually have an omnidirectional radiation pattern out to the sides, hence a circular radiation pattern.

Often the radiation pattern is referred to as doughnut-shaped.

Vertical whips are relatively non directional, and radiate well in all directions.

If antenna is sloped from vertical position, then it acquires a radiation pattern (or shape). This affects the antenna radiation efficiency. This means, it does not transmit equally in all directions.

In wire, the radiation power travels to the end of the wire, and does not provide radiation in all directions.

For great illustration of patterns, see Wikipedia article on Omnidirectional antenna

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