VHF Marine Radio

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A standard handheld maritime VHF, mandatory on larger vessels under the GMDSS rules

Marine VHF radio is installed on all large ships and most motorized small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours and marinas, and operates in the VHF frequency range, between 156 to 174 MHz. Although it is widely used for collision avoidance, its use for this purpose is contentious and is strongly discouraged by some countries, including the UK. ^[1]

A marine VHF set is a combined transmitter and receiver and only operates on standard, international frequencies known as channels. Channel 16 (156.8 MHz) is the international calling and distress channel. Channel 9 can also be used in some places as a secondary call and distress channel. Transmission power ranges between 1 and 25 watts, giving a maximum range of up to about 60 nautical miles (111 km) between aerials mounted on tall ships and hills, and 5 nautical miles (9 km) between aerials mounted on small boats at sea-level. ^[2] Frequency modulation is used.

Marine VHF mostly uses "simplex" transmission, where communication can only take place in one direction at a time. A transmit button on the set or microphone determines whether it is operating as a transmitter or a receiver. The majority of channels, however, are set aside for "duplex" transmissions channels where communication can take place in both directions simultaneously ^[3]. Each duplex channel has two frequency assignments. This is mainly because, in the days before mobile phones and satcomms became widespread, the duplex channels could be used to place calls on the public telephone system for a fee via a marine operator. This facility is still available in some areas, though its use has largely died out. In US waters, Marine VHF radios can also receive weather radio broadcasts, where they are available, on receive-only channels wx1, wx2, etc.

Types of equipment

Sets can be fixed or portable. A fixed set generally has the advantages of a more reliable power source, higher transmit power, a larger and more effective aerial and a bigger display and buttons. A portable set (often essentially a waterproof, VHF walkie-talkie in design) can be carried to a lifeboat in an emergency, has its own power source and is more easily water-proofed.

Marine radios can be "voice-only" or can include "Digital Selective Calling" (DSC).

Voice-only equipment is the traditional type, which relies totally on the human voice for calling and communicating. s

A VHF set and a VHF channel 70 DSC set, the DSC on top, both produced by Sailor

Digital Selective Calling equipment, a part of the Global Maritime Distress Safety System (GMDSS), provides all the functionality of voice-only equipment and, additionally, allows several other features:

• a transmitter can automatically call a receiver equipped with Digital Selective Calling, using a telephone-type number known as a Maritime Mobile Service Identity or MMSI. Such calls take place on Channel 70.
• a distress button, which automatically sends a digital distress signal identifying the calling vessel and the nature of the emergency
• a connection to a GPS receiver allowing the digital distress message to contain the distressed vessel's position

The MMSI is a nine digit number identifying a VHF set or group of sets. The left hand digits of MMSI indicate the country and type of station. For example, here are MMSI prefixes of four station types:

• Ship : 232 is the United Kingdom – e.g. a UK ship : 232003556
• Coast : 00 – e.g. Solent Coastguard : 002320011
• Group of stations : 0 – e.g. 023207823
• Portable DSC equipment : for UK 2359 - e.g. 235900498

Operating procedure

The accepted conventions for use of marine radio are collectively termed "proper operating procedure." These conventions include:

• Listening for 2 minutes before transmitting
• Using Channel 16 only to establish communication (if necessary) and then switch to a different channel
• using a set of international "calling" procedures such as the "Mayday" distress call, the "Pan-pan" urgency call and "Securité" navigational hazard call.
• using "pro-words" based on the English language such as Acknowledge, All after, All before, All stations, Confirm, Correct, Correction, In figures, In letters, Over, Out, Radio check, Read back, Received, Repeat, Say again, Spell, Standby, Station calling, This is, Wait, Word after, Word before, Wrong
• using the NATO phonetic alphabet: 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
• using a phonetic numbering system based on the English language: Wun, Too, Tree, Fow-er, Fife, Six, Sev-en, Ait, Nin-er, Zero, Decimal

Marine VHF radio is sometimes illegally operated inland. Since enforcement is often the job of the local coast guard, enforcement away from the water is sometimes difficult.

Marine VHF Channels and Frequencies

Channel number	"A" frequency (MHz) Usually ship stations	"B" frequency (MHz) Usually coast stations	United Kingdom	United States	Canada	Australia
0	156.000	160.600	Private, coast guard Ⓐ
1	156.050	160.650			Public Correspondence (Ship-to-Shore Duplex) BC Coast
2	156.100	160.700			Public BC Coast
3	156.150	160.750		Ⓐ Illegal for public use1	Public BC Coast/Inland
4	156.200	160.800			Ship-to-ship/shore, commercial and safety BC and East Coasts Ⓐ
5	156.250	160.850
6	156.300	160.900	Ship-to-ship Ⓐ
7	156.350	160.950
8	156.400	161.000	Ship-to-ship Ⓐ
9	156.450	161.050	Ship-to-ship Ⓐ	Calling Ⓐ, commercial and non-commercial.
10	156.500	161.100	Ship-to-ship Ⓐ
11	156.550	161.150
12	156.600	161.200
13	156.650	161.250	Ship-to-ship Ⓐ	Bridge-to-Bridge safety Ⓐ: Vessels > 20m must maintain watch, Tx limited to 1 watt.
14	156.700	161.300
15	156.750	161.350	Ship-to-ship Ⓐ
16	156.800	161.400	International distress, safety and calling Ⓐ USA: All vessels equipped with VHF must maintain watch.
17	156.850	161.450	Ship-to-ship Ⓐ
18	156.900	161.500
19	156.950	161.550
20	157.000	161.600
21	157.050	161.650		Ⓐ U.S. Coast Guard Only
22	157.100	161.700		Ⓐ U.S. Coast Guard—public working channel2
23	157.150	161.750		Ⓐ U.S. Coast Guard Only
24	157.200	161.800
25	157.250	161.850
26	157.300	161.900
27	157.350	161.950
28	157.400	162.000
60	156.025	160.625
61	156.075	160.675		Ⓐ Illegal for public use1
62	156.125	160.725
63	156.175	160.775
64	156.225	160.825		Ⓐ Illegal for public use1
65	156.275	160.875
66	156.325	160.925
67	156.375	160.975
68	156.425	161.275		Non-commercial Ⓐ
69	156.475	161.075		Non-commercial Ⓐ		Australian Navy
70	156.525	161.125	Digital Selective Calling Ⓐ
71	156.575	161.175		Non-commercial Ⓐ
72	156.625	161.225		Non-commercial ship-to-ship Ⓐ
73	156.675	161.275
74	156.725	161.325
75	156.775	161.375
76	156.825	161.425
77	156.875	161.475
78	156.925	161.525		Non-commercial Ⓐ
79	156.975	161.575
80	157.025	161.625
81	157.075	161.675		Ⓐ U.S. Government Use Only
82	157.125	161.725		Ⓐ U.S. Government Use Only
83	157.175	161.775		Ⓐ U.S. Coast Guard Use Only
84	157.225	161.825
85	157.275	161.875
86	157.325	161.925
87	157.375	161.975	Automatic Identification System Ⓑ
88	157.425	162.025	Automatic Identification System Ⓑ

Notes:

1: Some radios enable channels 3a, 61a, and 64a when configured for "USA mode" even though those channels are not listed for maritime use by the US Coast Guard or by the FCC. The frequencies in question appear to be used for land-mobile communication by police and fire departments in some US Cities.

2: Channel 22a is reserved for communication between the U.S. Coast Guard vessels and private vessels. The Coast Guard does not monitor 22a: Contact must first be established on 16.

See also

• 2182 kHz
• Maritime mobile amateur radio
• AIS System
• Radio horizon

References

1. ^ UK Maritime and Coastguard Agency Marine Guidance Note MGN324
2. ^ UK Maritime and Coastguard Agency Marine Guidance Note MGN324
3. ^ UK Maritime and Coastguard Agency Marine Guidance Note MGN324

External links

• US Coast Guard basic radio information for boaters
• US Coast Guard marine channel listing (with frequencies)
• US FCC marine channel listing (by function)
• UK MCA advice on use of VHF at sea, including collision avoidance, effective ranges, and International channel usage*
• Canadian VHF Bands in the Maritime Service
• UK Radio Training and Licence*