Under what circumstances may a ship or aircraft station interfere with a public coast station?

In cases of distress.

Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart
G Safety Watch Requirements and Procedures

§ 80.312 Priority of distress transmissions.

The distress call has absolute priority over all other transmissions.

All stations which hear it must immediately cease any transmission capable of interfering with the distress traffic and must continue to listen on the frequency used for the emission of the distress call.

This call must not be addressed to a particular station. Acknowledgement of receipt must not be given before the distress message which follows it is sent.

FCC regulations consider situations where the protection of life or property is involved, and permits interference with public coast station messaging.

Although the navigation or meteorological warnings may not involve immediate risk to life or property, but may develop into situations involving distress, safety, etc.

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Ordinarily, how often would a station using a telephony emission identify?

At the beginning and end of each transmission and at 15-minute intervals.

From Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 90
§ 90.425 Station identification.

47 CFR 90.425(a) Identification procedure. Except as provided for in paragraphs (d) and (e) of this section, each station or system shall be identified by the transmission of the assigned call sign during each transmission or exchange of transmissions, or once each 15 minutes (30 minutes in the Public Safety Pool) during periods of continuous operation.

The call sign shall be transmitted by voice in the English language or by International Morse Code in accordance with paragraph (b) of this section.

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When using a SSB station on 2182 kHz or VHF-FM on channel 16:

All of these.

• Preliminary call must not exceed 30 seconds.
• If contact is not made, you must wait at least 2 minutes before repeating the call.
• Once contact is established, you must switch to a working frequency.

Of course, when facing an emergency involving safety or loss of property, these limitations Do Not Apply.

§ 80.111 Radiotelephone operating procedures for coast stations.

47 CFR 80.111(a)(4) Calling a particular station must not continue for more than one minute in each instance. **If the called station does not reply, that station must not again be called for two minutes.

When a called station does not reply to a call sent three times at intervals of two minutes,** the calling must cease for fifteen minutes.

However, if harmful interference will not be caused to other communications in progress, the call may be repeated after three minutes.

47 CFR 80.111(b) Time limitation on calling frequency. Transmissions by coast stations on 2182 kHz or 156.800 MHz must be minimized and any one exchange of communications must not exceed one minute in duration.

47 CFR 80.111(c) Change to working frequency. After establishing communications with another station by call and reply on 2182 kHz or 156.800 MHz coast stations must change to an authorized working channel for the transmission of messages.

§ 80.116 Radiotelephone operating procedures for ship stations.

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.

47 CFR 80.116(d) Limitations on calling. Calling a particular station must not continue for more than 30 seconds in each instance. If the called station does not reply, the station must not again be called until after an interval of 2 minutes.

When a called station called does not reply to a call sent three times at intervals of 2 minutes, the calling must cease and must not be renewed until after an interval of 15 minutes; however, if there is no reason to believe that harmful interference will be caused to other communications in progress, the call sent three times at intervals of 2 minutes may be repeated after a pause of not less than 3 minutes. In event of an emergency involving safety, the provisions of this paragraph do not apply.

For more info, please see US Coast Guard article on GMDSS FREQUENTLY ASKED QUESTIONS

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What should a station operator do before making a transmission?

Except for the transmission of distress calls, determine that the frequency is not in use by monitoring the frequency before transmitting.

For all radio wave transmission, one should listen before initiating a message. This helps to prevent jumping on top of someone already speaking.

Always LISTEN first.

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

§ 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.

For good info on radio etiquette, please see California State University guidance on Two-Way Radio Protocol

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On what frequency should a ship station normally call a coast station when using a radiotelephony emission?

Calls should be initiated on the appropriate ship-to-shore working frequency of the coast station.

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

NOTE:> Please look over the H - Frequencies Subpart, as it lists frequency assignments and tables, just to familiarize yourself with how FCC categorizes purposes and frequencies.

Below is a listing of references for specific situations, identified in Subpart H - Frequencies, that is important to become aware of.

§ 80.355 Distress, urgency, safety, call and reply Morse code frequencies.

This section describes the distress, urgency, safety, call and reply carrier frequencies assignable to stations for Morse code radiotelegraphy.

NOTE:> Please look over the sections below just to familiarize yourself with the detailed specific info.

47 CFR 80.355(a) Frequencies in the 100-160 kHz band

47 CFR 80.355(b) Frequencies in the 2000-27500 kHz band

• 47 CFR 80.355(b)(1) Ship station frequencies.
  
• 47 CFR 80.355(b)(2) Coast Station frequencies
  

47 CFR 80.355(c) Frequencies in the VHF bands.

• 47 CFR 80.355(c)(1) Survival craft stations
  
• 47 CFR 80.355(c)(2) EPIRB stations
  

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In the International Phonetic Alphabet, the letters E, M, and S are represented by the words:

Echo, Mike, Sierra

Alpha, Bravo, Charlie, Delta,
Echo, Foxtrot, Golf, Hotel,
India, Juliet, Kilo, Lima,
Mike, November, Oscar, Papa,
Quebec, Romeo, Sierra, Tango,
Uniform, Victor, Whiskey
X-ray, Yankee, Zulu

See NATO Phonetic Alphabet

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