Marine VHF 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 seagoing small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks, bridges 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, with vertical polarization, meaning that antennas have to be vertical in order to have good reception.

Modern day marine VHF radios have a variety of features in addition to basic transmit and receive capabilities. All fixed mount marine VHF radios produced nowadays have some level of DSC calling capability. A number of the more expensive units are capable of acting as a hailer when connected to a hailer horn, can work with optional voice scramblers, and a few even have the ability to use a Bluetooth headset.

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" (DSC).

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

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. The DSC information is send on the reserved Channel 70. When the receiver picks up the call, his active channel is automatically switched to the transmitter's channel and normal voice communication can proceed.
  • 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, 233, 234 or 235 are 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

Slightly adjusted regulations can apply for inland shipping, such as the Basle rules in Western Europe.

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		  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 + Ship-to-Air Ⓐ
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 Canadian Coast Guard - Working Channel
20 157.000 161.600
21 157.050 161.650 Ⓐ U.S. Coast Guard Only Continuous Marine Broadcasts Ⓑ (WX 8)
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 UKSAR G/A Winching Ⓐ
UKSAR TWC Ⓑ
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 UKSAR Calling & Helicopter Channel Ⓐ
UKSAR TWC Ⓑ
63 156.175 160.775 UKSAR TWC (simplex)
64 156.225 160.825 UKSAR TWC (simplex) Ⓐ Illegal for public use1
65 156.275 160.875 Marine Assistance Working Channel
66 156.325 160.925
67 156.375 160.975 HM Coastguard Search & Rescue
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 Ship-to-ship Ⓐ Non-commercial ship-to-ship Ⓐ
73 156.675 161.275 HM Coastguard Safety Broadcasts
74 156.725 161.325 British Waterways Channel (Canal System)
75 156.775 161.375
76 156.825 161.425
77 156.875 161.475 Ship-to-ship Ⓐ
78 156.925 161.525 Non-commercial Ⓐ
79 156.975 161.575
80 157.025 161.625 Marinas UK Only
81 157.075 161.675 Ⓐ U.S. Government Use Only
82 157.125 161.725 Ⓐ U.S. Government Use Only Canadian Coast Guard - Working Channel
83 157.175 161.775 Ⓐ U.S. Coast Guard Use Only Continuous Marine Broadcasts Ⓑ (WX 9)
84 157.225 161.825
85 157.275 161.875 UKSAR TWC (simplex) Radio Telephone - Duplex
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.

3: UKSAR land based search & reacue teams have access to the simplexed versions of 24, 62, 63, 64, 85 for operational & training needs. These include Mountain Rescue teams in England, Wales & Scotland.

[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

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