Marine Communications

Aim and Objectives Aim: To summarize marine communications Associated Objectives, by the end of the session you should be able to: to understand the services offered by VHF to understand the principles of GMDSS 2

Why Marine Communications? Although telecommunications technology is improving quickly, ships at sea do not have access to the same telecommunications infrastructure persons ashore have.

Why Marine Communications? Mariners not only need to access international shore telephone and data public switched networks, they need to be able to communicate with other ships of any size or nationality, to receive and send urgent maritime safety information, to send or receive distress alerts in an emergency to or from rescue co-ordination centres ashore and nearby ships anywhere in the world.

Why Marine Communications? Unlike cellular telephones and land mobile radios used in the United Kingdom, maritime telecommunications systems must be internationally interoperable, even in United Kingdom coastal waters, where numerous foreign ships sail.

Why Marine Communications? Bringing new telecommunications technology to mariners can be difficult, since to be interoperable, the technology must be affordable, acceptable and available to most ships and maritime countries.

Administration of Marine Communications Two United Nations-chartered organisations, the International Maritime Organisation and the International Telecommunications Union, are responsible for defining and regulating maritime telecommunications systems. The most current system adopted by these two organisations is the Global Maritime Distress and Safety System, or GMDSS.

An Overview of GMDSS Since the invention of radio at the end of the 19th Century, ships at sea have relied on Morse code, invented by Samuel Morse and first used in 1844, for distress and safety telecommunications. 5

An Overview of GMDSS The need for ship and coast radio stations to have and use radiotelegraph equipment, and to listen to a common radio frequency for Morse encoded distress calls, was recognised after the sinking of the liner Titanic in the North Atlantic in 1912.

An Overview of GMDSS The U.S. Congress enacted legislation soon after, requiring U.S. ships to use Morse code radiotelegraph equipment for distress calls. The International Telecommunications Union (ITU), now a United Nations agency, followed suit for ships of all nations. 6

An Overview of GMDSS Morse encoded distress calling has saved thousands of lives since its inception almost a century ago, but its use requires skilled radio operators spending many hours listening to the radio distress frequency. Morse’s range on the medium frequency (MF) distress band (500 kHz) is limited, and the amount of traffic Morse signals can carry is also limited. 7

An Overview of GMDSS Over fifteen years ago the International Maritime Organisation (IMO), a United Nations agency specialising in safety of shipping and preventing ships from polluting the seas, began looking at ways of improving maritime distress and safety communications. In 1979, a group of experts drafted the International Convention on Maritime Search and Rescue, which called for development of a global search and rescue plan.

An Overview of GMDSS This group also passed a resolution calling for development by IMO of a Global Maritime Distress and Safety System (GMDSS) to provide the communication support needed to implement the search and rescue plan. 8

An Overview of GMDSS This new system, which the world's maritime nations, including the United Kingdom, are implementing, is based upon a combination of satellite and terrestrial radio services. It has changed international distress communications from being primarily ship-to-ship based to ship-to-shore (Rescue Co-ordination Centre) based.

An Overview of GMDSS It spelled the end of Morse code communications for all but a few users, such as Amateur Radio. The GMDSS provides for automatic distress alerting and locating in cases where a radio operator doesn't have time to send an SOS or MAYDAY call, and, for the first time, requires ships to receive broadcasts of maritime safety information which could prevent a distress from happening in the first place. 9

GMDSS The GMDSS consists of several systems, some of which are new, but many of which have been in operation for many years. The system will be able to reliably perform the following functions: alerting (including position determination of the unit in distress), search and rescue co-ordination, locating (homing), maritime safety information broadcasts, general communications, bridge-to-bridge communications. 10

GMDSS Specific radio carriage requirements depend upon the ship's area of operation, rather than its tonnage. A ship's area of operation is defined as follows: Sea area Al. An area within the radiotelephone coverage of at least one VHF coast station in which continuous DSC alerting is available as defined by the International Maritime Organisation. 11

GMDSS Sea area A2. An area, excluding sea area Al, within the radiotelephone coverage of at least one MF coast station in which continuous DSC alerting is available as defined by the International Maritime Organisation. Sea area A3. An area, excluding sea areas Al and A2, within the coverage of an INMARSAT geostationary satellite in which continuous alerting is available. Sea area A4. An area outside sea areas Al, A2 and A3.

VHF Radio Principles The VHF is the most common and cheapest form of radio communication available for marine use. 12

VHF Radio Principles If travel of more than a few miles offshore is to be undertaken, consideration should be made for the purchase of an HF radiotelephone or mobile satellite telephone, an EPIRB, and a second, portable VHF radio or cellular telephone as well.

VHF Radio Principles Mobile satellite telephones are becoming more common and more inexpensive. The mobile satellite will provide easier and clearer communications than the HF radiotelephone, but the HF radiotelephone will provide high seas marine weather warnings. 13

VHF Radio Principles VHF radio can operate on frequencies between 30 and 300 MHz but certain areas of this wide frequency band or reserved for selected users. The standard marine VHF frequencies are between 156 and 163 MHz. 156.8 MHz has been designated as the calling and distress frequency on which all vessels and coast radio stations listen to. A table of International channels is available.

VHF Radio Principles For ease of use the VHF channels have been designated a number from 1 to 88, the distress and calling channel is Channel 16. The table of frequencies and channels shows that some frequencies are missing. These have been designated for private use, these have a frequency range of 162.05 MHz to 174.00 MHz. 14

VHF Radio Principles They are allocated by the relevant maritime government to its nationals on a private and exclusive basis. These private channels are utilised by ferry companies, towing and salvage operators, surveying and diving companies. 15

VHF Radio Principles An example of a private channel is the frequency 157.85 MHz. this has been designated by the British Government for British marinas a yacht clubs and is known as Channel M or 37. This is a private British channel which only operates in the UK and only British marinas, yacht clubs and British yachts are authorised to use it.

VHF Operation VHF radios can be operated in Simplex or Duplex mode. The Simplex method means that only one party in a two way exchange can talk at one time, at the end of the conversion the user has to say "over" to indicate it is the other party's turn to speak. Simplex is the most common form of VHF. 16

VHF Operation Duplex utilises two channels, one to receive and one to transmit. The channels are selected automatically through a single channel number. The Duplex system is mainly used for telephone links.

VHF Operation VHF radio provides the user with slightly greater than line-of-sight communications. There is therefore a requirement for the antenna of the transmitting radio to be visible to the receiving aerial without the curvature of the earth or physical and geographical features interfering with the signal. 17

VHF Operation The transmitted signal follows the curvature of the earth very slightly thus increasing range form line of sight. To obtain maximum range the antenna needs to be as high as possible.

VHF Operation On small craft VHF range will be limited due to relatively low antenna heights resulting in vessel to vessel range of 10 - 15 miles whereas vessel to shore range is about 40 miles and figures in excess of this can be achieved given the right conditions. 18

Services available through VHF radio Channel 16 and priority of signals Distress - MAYDAY Communication with other vessels Communication with the Coastguard Communication with Harbourmasters Communication with Marina and Yacht Clubs Communication with Coast Radio Stations and Ship-to-Shore calls Broadcasts by Coast Radio Stations 19

Summary Why Marine communication Administration of Marine communication GMDSS VHF Radio Principles VHF Operation