Marine VHF radio

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

Contents

[edit] 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".

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

A VHF set and a VHF channel 70 DSC set, the DSC on top, both produced by Sailor
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 GMDSS, provides all the functionality of voice-only equipment and, additionally, allows several other features:

  • a transmitter can call a receiver automatically using Digital Selective Calling on Channel 70, using a telephone-type number known as a Maritime Mobile Service Identity or MMSI
  • 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

[edit] 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.

[edit] Marine VHF Channels and Frequencies

Channel
number		 "A" frequency (MHz)
Usually ship stations		 "B" frequency (MHz)
Usually coast stations		 Flag of the United Kingdom United Kingdom Flag of the United States United States Flag of Canada Canada Flag of Australia 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 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 Ⓐ
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 Ⓐ
14 156.700 161.300
15 156.750 161.350 Ship-to-ship Ⓐ
16 156.800 161.400
International distress, safety and calling Ⓐ
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
22 157.100 161.700
23 157.150 161.750
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
62 156.125 160.725
63 156.175 160.775
64 156.225 160.825
65 156.275 160.875
66 156.325 160.925
67 156.375 160.975
68 156.425 161.275
69 156.475 161.075
70 156.525 161.125 Digital Selective Calling Ⓐ
71 156.575 161.175
72 156.625 161.225
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
79 156.975 161.575
80 157.025 161.625
81 157.075 161.675
82 157.125 161.725
83 157.175 161.775
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 Ⓑ

[edit] See also

[edit] 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

[edit] External links

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Two-way radio
Amateur and hobbyist
Aviation (aeronautical mobile)
Land-based commercial and government mobile
Marine (shipboard)
Signaling / Selective calling
System elements and principles