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Subelement C
Equipment Operations
Section 16
MF-HF Frequency & Emission Selection
On what frequency would a vessel normally call another ship station when using a radiotelephony emission?
  • Only on 2182 kHz in ITU Region 2.
  • Correct Answer
    On 2182 kHz or Ch-16, unless the station knows that the called vessel maintains a simultaneous watch on another intership working frequency.
  • On the appropriate calling channel of the ship station at 15 minutes past the hour.
  • On the vessel’s unique working radio channel assigned by the Federal Communications Commission.

On what frequency would a vessel normally call another ship station when using a radiotelephony emission?

(B). On 2182 kHz or Ch-16, unless the station knows that the called vessel maintains a simultaneous watch on another inter-ship working frequency.

Channel 16 is used for MF NAVTEX. It can be used only in English for Distress, Urgency, Safety and Calling.

Please see US Coast Guard article on HF DISTRESS AND USCG CONTACT FREQUENCIES for detailed info.


2182 kHz frequency is used for MF R/T Distress. It may be used for ship-to-ship alerting.

As the 2182 kHz was used "minimally," the United States Coast Guard no longer maintain a watch on 2182 kHz, since 2013.
See: Federal Register announcement


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

§ 80.116 Radiotelephone operating procedures for ship stations.

47 CFR 80.116(b) Calling ship stations.

47 CFR 80.116(b)(1) Except when other operating procedure is used to expedite safety communication, ship stations, before transmitting on the intership working frequencies 2003, 2142, 2638, 2738, or 2830 kHz, must first establish communications with other ship stations by call and reply on 2182 kHz. Calls may be initiated on an intership working frequency when it is known that the called vessel maintains a simultaneous watch on the working frequency and on 2182 kHz.

47 CFR 80.116(b)(2) Except when other operating procedures are used to expedite safety communications, the frequency 156.800 MHz must be used for call and reply by ship stations and marine utility stations before establishing communication on one of the intership working frequencies. Calls may be initiated on an intership working frequency when it is known that the called vessel maintains a simultaneous watch on the working frequency and on 156.800 MHz.

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What is the MF radiotelephony calling and Distress frequency?
  • 2670 kHz.
  • Ch-06 VHF.
  • Correct Answer
    2182 kHz.
  • Ch-22 VHF.

What is the MF radiotelephony calling and Distress frequency?

(C). 2182 kHz.

MF radiotelephony frequency of 2182 kHz (class J3E) and Ch16 (156.8 MHz) are used for distress, urgency and safety communications and for contacting.


Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart H Radiotelephony

§ 80.369 Distress, urgency, safety, call and reply frequencies.

47 CFR 80.369(a) In the 1605-3500 kHz band, the frequency 2182 kHz is an international radiotelephony distress, urgency and safety frequency for ship stations, public and private coast stations, and survival craft stations.

It is also used for call and reply by ship stations on a primary basis and by public coast stations on a secondary basis.

The carrier frequency 2191 kHz may be used as a supplementary calling frequency in areas of heavy usage of 2182 kHz .

All stations must use J3E emission when operating on 2182 kHz and 2191 kHz, except that:

47 CFR 80.369(a)(1) H3E emission may be used on 2182 kHz for communications with foreign coast and ship stations; or,

47 CFR 80.369(a)(2) A3E emission may be used on 2182 kHz by portable survival craft stations, or transmitters authorized for use prior to January 1, 1972.

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For general communications purposes, paired frequencies are:
  • Normally used with private coast stations.
  • Normally used between ship stations.
  • Normally used between private coast and ship stations.
  • Correct Answer
    Normally used with public coast stations.

For general communications purposes, paired frequencies are:

(D). Normally used with public coast stations.

§ 80.369 - Distress, urgency, safety, call and reply frequencies.

47 CFR 80.369(d) In the 4000-27500 kHz band, the following coast frequencies are available for assignment to public coast stations for call and reply communications. The paired ship frequencies are available for use by authorized ship stations.

Please see the detailed table under the above paragraph, entitled "Call and Reply Frequency Pairs in the 4000-27500 kHz."

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What emission must be used when operating on the MF distress and calling voice frequency?
  • Correct Answer
    J3ESingle sideband telephony.
  • A1A – On-off keying without modulation by an audio frequency.
  • F3E – Frequency modulation telephony.
  • A3E – Amplitude modulation telephony, double sideband.

What emission must be used when operating on the MF distress and calling voice frequency?

(A). J3E – Single sideband telephony.

J3E/SSB is the standard operating mode for voice on HF frequencies in GMDSS. Note that 2182 KHz is a frequency for which USB and extremely rarely AM, is used.

F3E (Frequency modulation)/FM is the standard operating mode for voice on VHF frequencies.

A1A/CW/On-Off is used for telegraphy.

A3E/AM is a DSB modulation mode used mainly for air band broadcast communications. Note that 121.500 MHz is a distress frequency for which AM is used.

For more info, please see Wikipedia's article Types of radio emissions

For excellent overview, please see GMDSSTesters site for article on General principles and features of Maritime Mobile Service


Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart H Radiotelephony

§ 80.369 Distress, urgency, safety, call and reply frequencies.

47 CFR 80.369(a) In the 1605-3500 kHz band, the frequency 2182 kHz is an international radiotelephony distress, urgency and safety frequency for ship stations, public and private coast stations, and survival craft stations.

It is also used for call and reply by ship stations on a primary basis and by public coast stations on a secondary basis.

The carrier frequency 2191 kHz may be used as a supplementary calling frequency in areas of heavy usage of 2182 kHz .

All stations must use J3E emission when operating on 2182 kHz and 2191 kHz, except that:

47 CFR 80.369(a)(1) H3E emission may be used on 2182 kHz for communications with foreign coast and ship stations; or,

47 CFR 80.369(a)(2) A3E emission may be used on *2182 kHz by portable survival craft stations, or transmitters authorized for use prior to January 1, 1972.

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Which of the following defines high frequency “ITU Channel 1212”?
  • Ch-12 in the 16 MHz band.
  • Ch-1216 in the MF band.
  • Correct Answer
    The 12th channel in the 12 MHz band.
  • This would indicate the 1st channel in the 12 MHz band.

Which of the following defines high frequency “ITU Channel 1212”?

(C). The 12th channel in the 12 MHz band.

ITU stands for International Telecommunications Union, which is a United Nations agency.

Within the ITU, there is a division called ITU-R, a (R) radio communication group that directs radio frequency spectrum assignments and frequency allocations for the orbiting satellites.

See Wikipedia's article on International Telecommunication Union and ITU Radiocommunication

ITU channels follow the format of mmcc where mm is the band in MHz and cc is the channel number.

The ITU Channel 1212 for ships is the frequency of 12,263 kHz, or 12.263 MHz, and for coast originating transmissions is 13,110 kHz, or 13.110 MHz.

For detailed info, please see US Coast Guard article on 12 MHz Duplex Channels

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For general communications purposes, simplex frequencies are:
  • Normally used between ship stations and private coast stations.
  • Normally used with public coast stations.
  • Normally used between ship stations.
  • Correct Answer
    Both a) and c) are correct.

For general communications purposes, simplex frequencies are:

(D). Both a) and c) are correct.

  • a. Normally used between ship stations and private coast stations.
  • c. Normally used between ship stations.

Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart H - Frequencies

§ 80.373 Private communications frequencies.

47 CFR 80.373(c) Frequencies in the 2000-27500 kHz bands for business and operational communications.

47 CFR 80.373(c)(1) The following simplex frequencies in the 2000-27500 kHz band are available for assignment to private coast stations for business and operational radiotelephone communications.

These simplex frequencies also are available for use by authorized ship stations for business and operational radiotelephone communications.

NOTE:> The CFR Part 80 Subpart H - Frequencies contains 29 references to Simplex channel assignments. Please click on the H-Frequencies, and in the web site, use Ctrl-F, and search on word "simplex" to see where simplex assignments are used. The reference above appears to be most relevant here.

For channel assignment, please see US Coast Guard HF Simplex Channels

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