What is the best way for a radio operator to minimize or prevent interference to other stations?

Determine that a frequency is not in use by monitoring the frequency before transmitting.

The accepted practice in radio communications is to listen before initiating a communication. This prevents jumping on top of someone's continuing radio message.

• By using an omni-directional antenna pointed away from other stations. NOT CORRECT as pointing an omnidirectional antenna an omnidirectional antenna which radiates equally in all directions does not prevent interference or anything else.

• Reducing power to a level that will not affect other on-frequency communications. NOT CORRECT as reducing power reduces potential recipients of radio communications, and does not prevent interference for those able to receive the signal.

• By changing frequency when notified that a radiocommunication causes interference. NOT CORRECT as changing frequency does not prevent interference in the first place. And, even if you change it, you must listen first. Otherwise, you will be interfering on that frequency also.

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

§ 80.92 Prevention of interference.

47 CFR 80.92(a) The station operator must determine that the frequency is not in use by monitoring the frequency before transmitting, except for transmission of signals of distress.

47 CFR 80.92(b) When a radiocommunication causes interference to a communication which is already in progress, the interfering station must cease transmitting at the request of either party to the existing communication. As between non distress traffic seeking to commence use of a frequency, the priority is established under § 80.91.

47 CFR 80.92(c) Except in cases of distress, communications between ship stations or between ship and aircraft stations must not interfere with public coast stations.

The ship or aircraft stations which cause interference must stop transmitting or change frequency upon the first request of the affected coast station.

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Under what circumstances may a coast station using telephony transmit a general call to a group of vessels?

When announcing or preceding the transmission of Distress, Urgency, Safety or other important messages.

Title 47 Chapter I Subchapter D Part 80 Subpart
J - Public Coast Stations

47 CFR 80.453(a) Public coast stations are authorized to communicate:

• 47 CFR 80.453(a)(1) With any ship or aircraft station operating in the maritime mobile service, for the transmission or reception of safety communication;

Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart Subpart
K Private Coast Stations and Marine Utility Stations

§ 80.507 Scope of service.

• 47 CFR 80.507(a) A private coast station or marine utility station using telephony serves the operational and business needs of ships including the transmission of safety communication.

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

80.89 Unauthorized transmissions.

Stations must not:

• 47 CFR 80.89(e) Transmit while on board vessels located on land unless authorized under a public coast station license. Vessels in the following situations are not considered to be on land for the purposes of this paragraph:

  • (1) Vessels which are aground due to a distress situation;
  • (2) Vessels in drydock undergoing repairs; and
  • (3) State or local government vessels which are involved in search and rescue operations including related training exercises.

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Who determines when a ship station may transmit routine traffic destined for a coast or government station in the maritime mobile service?

Ship stations must comply with instructions given by the coast or government station.

Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart
K - Private Coast Stations and Marine Utility Stations

§ 80.503 - Cooperative use of facilities.

47 CFR 80.503(a) A person engaged in the operation of one or more commercial transport vessels or government vessels may receive maritime mobile service from a private coast station or a marine utility station on shore even though not the licensee of the private coast station or the marine utility station.

47 CFR 80.503(a)(2) ... In each case these persons must enter into a written agreement verifying that the ship station licensee has the sole right of control of the ship stations, that the vessel operators must use the ship stations subject to the orders and instructions of the coast station or marine utility station on shore, and that the ship station license will have sufficient control of the ship station to enable it to carry out its responsibilities under the ship station license.

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What is required of a ship station which has established initial contact with another station on 2182 kHz or Ch-16?

The stations must change to an authorized working frequency for the transmission of messages.

After a distress signal has been answered, the conversation must be moved to another channel so that the distress channel remains available for others that may be in distress.

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

§ 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.

47 CFR 80.116(c) Change to working frequency. After establishing communication with another station by call and reply on 2182 kHz or 156.800 MHz stations on board ship must change to an authorized working frequency for the transmission of messages.

Please see US Coast Guard VHF Channel Info - very useful

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How does a coast station notify a ship that it has a message for the ship?

The coast station may transmit, at intervals, lists of call signs in alphabetical order for which they have traffic.

Title 47 Chapter I Subchapter D Part 80 Subpart
C Operating Procedures - Land Stations

§ 80.108 Transmission of traffic lists by coast stations.

47 CFR 80.108(a) Each coast station is authorized to transmit lists of call signs in alphabetical order of all mobile stations for which they have traffic on hand. These traffic lists will be transmitted on the station's normal working frequencies at intervals of:

• 47 CFR 80.108(a)(1) In the case of telegraphy, at least two hours and not more than four hours during the working hours of the coast station.

• 47 CFR 80.108(a)(2) In the case of radiotelephony, at least one hour and not more than four hours during the working hours of the coast station.

47 CFR 80.108(b) The announcement must be as brief as possible and must not be repeated more than twice. Coast stations may announce on a calling frequency that they are about to transmit call lists on a specific working frequency.

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What is the priority of communications?

Distress, Urgency and Safety.

§ 80.91 Order of priority of communications.

47 CFR 80.91(a) All stations in the maritime mobile service and the maritime mobile-satellite service shall be capable of offering four levels of priority in the following order:

• 47 CFR 80.91(a)(1) Distress calls, distress messages, and distress traffic.

• 47 CFR 80.91(a)(2) Urgency communications.

• 47 CFR 80.91(a)(3) Safety communications.

• 47 CFR 80.91(a)(4) Other communications.

47 CFR 80.91(b) In a fully automated system, where it is impracticable to offer all four levels of priority, category 1 shall receive priority until such time as intergovernmental agreements remove exemptions granted for such systems from offering the complete order of priority.

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