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Cape Town Radio “the Sharp End Of It All”

Cape Town Radio “the sharp end of it all”

The following article was kindly done by John Prinsloo of Cape Town Radio, who came to present at one of our Winter Wednesday Talks. From Wednesday 6th August.

Communication consists of a sender passing information to a receiver by various means. SAR personnel, survivors, RCCs and RSCs and SAR facilities must have the means to be senders and receivers. SAR managers must seek to provide the essential communications elements to receive distress alerts and to perform the SAR mission and to promote the use of appropriate alerting equipment by those who may need SAR services. Necessary communications for SAR may include telephones, radios operating on international distress frequencies, long-range terrestrial and satellite systems, and other equipment, depending upon geography, the capabilities of mobile facilities within that area, and other factors affecting the ability of persons to contact each other.

There is a need to build personnel competence; to improve communications, to understand how communication services are actually used for distress alerting, Timely delivery of alerts should be increasingly achieved as IMO and ICAO and our own SAR Plans continue to improve. Information must be complete, accurate and easy to understand. Alerts with coded or missing data, wrong aircraft or vessel identities or positions, are detrimental to lifesaving.

RCCs consider every alert received to be related to a real distress. Systems intended for distress alerting should be reliable. Equipment for distress alerting must be registered from when it is installed. False alerts are any alerts received by the SAR system which indicate an actual or potential distress situation, when no such situation actually exists. Some causes of false alerts include equipment malfunctions, interference, testing, and inadvertent human error. A false alert transmitted deliberately is called a hoax. It is essential that SAR personnel treat every distress alert as genuine until they know differently. If the vessel or aircraft sending an alert is still operational, an RCC should be able to contact it directly or via an appropriate communications facility on the same equipment it used to contact the RCC.

Important factors that affect the quality and usefulness of communications:

  • Priority – What matters is the overall timeliness and quality of communications from their source to final destination.
  • Reliability is a measure of whether equipment and systems used by persons in distress and providers of SAR services are in good working condition.
  • Availability refers to the SAR providers’ access to equipment. Every civil vessel and aircraft should have basic alerting equipment which will be effective for the area in which they operate.
  • Cape Town Radio receives processes and routes distress alerts to the ARCC/MRCC
  • All radio transmission sources must be identifiable.
  • Geography and available Technology must be considered.

Many types of communications systems and equipment are available. Basic communications may be all that are needed to provide SAR services; sophisticated and expensive systems may not be the most effective. However, technological advances, like the Internet and low earth orbit satellites, are providing potential low cost alternatives to older systems.

Persons in distress may use any means available to call for help. If a system gains public popularity, the SAR system should accommodate (not necessarily encourage) its use where practicable. Cellular telephones, low-power mobile satellite equipment, paging systems, amateur radios, and portable computers are examples.

SAR personnel should be aware of capabilities and limitations of the various modern means of communications.

Anyone receiving a distress call must immediately cease any transmissions which may interfere with the call and listen on the frequency used for the call. Inadvertent, false alarms must be cancelled [and must be cancelled via the nearest coast radio station]

Alerts are often received with missing or inaccurate position information. Location allows SRUs to be dispatched to the immediate vicinity of the distress; while direction finding or homing devices, if available, lead the SRU directly to the distressed persons.

The ability of an RCC to respond to an emergency depends largely on information forwarded via alerting posts like Cape Town Radio.

Perhaps the most important of the above data is the emergency contacts.

SAR managers must ensure that the GMDSS Master Plan has current information

The Master Plan shows for every State, in list format and on maps, which services are operational and planned.

VHF, MF and HF digital selective calling (DSC) installations; Inmarsat, SafetyNET, NAVTEX, and HF narrow-band direct printing services; satellite EPIRB registration, MCC and LUT information; and which RCCs are using [Ship Earth Stations] SESs.

Supplemental Capabilities include: Instant replay recording equipment to record aeronautical and maritime voice communications – equipment installed for telephone lines, such as answering machines, voice mail, call forwarding, automatic speed dialing and re-dialing, and caller identification can provide recorded announcements and invite the caller to leave a message, save time and reduce errors but these labour saving devices are no substitute for 24-hour watch standing and this is what we do.

Before radio communication was invented or introduced, ships captains used various means of communicating amongst each other from leaving notes under a rock to messages in a bottle. In 1895, a Russian professor, Alexander Popov, reported sending and receiving, a wireless signal across a distance of some 600 metres. In the same year, Guglielmo Marconi managed to transmit and receive radio signals at home in Italy and a land station in Kronstadt and a Russian cruiser conducted Wireless Telegraphy ship-to-shore communications. In 1901, Marconi sent transatlantic radio signals from south-western England to Newfoundland. Wireless signals proved to be effective in communications with ships in distress.

1n 1906 the first International Radiotelegraph Conference established the principle of compulsory intercommunication between land and vessels at sea and the first radio regulations governing Wireless Telegraphy were written.

Canadian Reginald Fessenden, made the first radio broadcast of the human voice in 1906.

1910 – Jacobs Radio was established [inland Brighton Beach – some years later it changed location to Pinetown and became known as Durban Radio – Cape Town Radio VNC was first established in 1913 at the old lighthouse site in Kommetjie – In 1928 the call-sign ZSC was allocated and is still in use today. The Mayor of Port Elizabeth opened Port Elizabeth Radio in May 1921. The first message was received from the motor vessel Armadale Castle at 1150 that day. She was 165 nautical miles SW of Port Elizabeth.

During World War Two, Cape Town Radio played a valuable role by intercepting distress messages from allied ships under German attack. It is recorded that on one occasion the station monitored eight distress calls in ten minutes.  Towards the middle of the war, the station moved to Wireless Road in Kommetjie where it shared premises with the Royal Navy and in September 1965 our address changed to Koeberg Road, Milnerton – these were the vacated premises of the South African Broadcasting Corporation. Cape Town Radio established itself on the world maritime map in 1967 when the Suez Canal was closed – we controlled communication traffic for thousands of ships that diverted to the Cape route. Additional operator circuits had to be manufactured, transmitters for the overflow traffic were provided by stations in the Transvaal, slave circuits on each band were opened and a record number of messages were transmitted and received daily. Congestion was just as bad at the ports. Frequently there were >100 ships at anchor in Table Bay seeking bunkers, stores and water. Over the years, radio telephony, Radio Teletype Telex-Over-Radio and E-mail-Over-Radio and satellite communications were introduced and older methods of communication were terminated. In March ’97 we moved to our existing premises in Bosmansdam Road in Milnerton. In March 2000 we closed WT on 5 ton and HF WT a year thereafter.

In 2003, we centralized Durban and Port Elizabeth Radio to Cape Town and so today, Cape Town, Port Elizabeth and Durban Radio and the South African COSPAS-SARSAT Local User Terminal and Mission Control all exist in the same building in Milnerton in Cape Town. With a main transmitter site in Klipheuwel, and main receiver site in Yzerfontein, everything else around the coast, is remote controlled from Cape Town Radio.

The goal of the International Civil Aviation Organization and of the International Maritime Organization is to provide an effective world-wide system, so that wherever people sail or fly, search and rescue services will be available if needed.

The South African Search & Rescue Organization is made up of representatives from various Government Departments, voluntary and private organizations able to contribute services and facilities.

  • Operational coordination of Aeronautical Search and Rescue is managed by the ATNS.
  • The Maritime Search and Rescue component has numerous role players:
  • The Maritime Rescue Co-ordination Centre is staffed by SAMSA personnel.
  • The Maritime Rescue Sub-Centres are staffed by the National Ports Authority.
  • SAR Maritime Radio and Satellite Communications facilities are staffed by Telkom.

The world’s oceans are divided into 21 NAV/MET/SAR areas of sea, for the dissemination of navigational warnings, weather warnings and forecasts and for search and rescue coordination. We look after AREAVII – The Search and Rescue Region of South Africa covers the entire South African coastal area; extends down to the South Pole, half way to South America to the West, and half way to Australia in the East – this is an area of some 28 million square miles. The National Department of Transport is responsible for compliance with the country’s responsibilities under the international SOLAS agreement.

Telkom Maritime is proud to have been contracted and entrusted by Government to be the associated SOLAS service provider – this 24-hour service includes radio, data and E-mail communications to and from any type of vessel anywhere in the world – we operate a network of radio stations around the South African coast – we keep watch on international Global Maritime Distress and Safety voice, digital and satellite systems – we track satellites that search the earth for transmitting emergency beacons and we broadcast Maritime Safety Information to vessels in the coastal and high seas Atlantic and Indian Ocean Regions.

We accept AMVER/ISPS/PORTHEALTH quarantine reports, SAFREP position reports and we are the GMDSS communications provider for the NAV/MET/SAR VII area coordinators VIZ: Hydrographer of the S.A. Navy, Director of the SAWS and the MRCC in Plattekloof.

In the GMDSS, two systems [NAVTEX and SafetyNET] are used to disseminate Maritime Safety Information. Some administrations still issue navigational warnings by other means, as we do per RT broadcasts for the benefit of small craft not adapted to the GMDSS.

Because of little demand, many countries have already, or are contemplating terminating RT broadcasts – The Cape Town, Port Elizabeth and Durban Radio weather bulletin and navigational warnings in force are combined and presented as one single-voice broadcast at 1015 and 1815 UTC – a coastal weather report as at 1200 UTC daily is presented at 1333 – transmission is affected on 4375, 8740 and 13146 kHz and on all available VHF traffic channels. VHF sites range from Alexander Bay on the West Coast to Kosi Bay in the East.

The concept of the GMDSS began as an idea at the IMO in 1973 and it finally entered into force in February 1999. The requirement for ships to comply with the GMDSS applies to all passenger vessels and all cargo vessels over 300 GT, if they are on international voyages. The master plan shows the detail behind the world network of inter-connected RCCs, each responsible for a given search and rescue region. Pleasure yachts not engaged in trade are not required to comply with the GMDSS but they are encouraged to participate on a voluntary basis and ultimately one day, all vessels will be required to adapt to this system.

In the GMDSS, 4 areas are defined:

  • A1 – within range of shore-based VHF stations
  • Ch70/DSC – Ch16/RT + 406 EPIRB + [9GHz SART/VHF radio for the survival craft]
  • A2 – within range of shore-based MF stations
  • As above plus MF radio 2187.5 DSC/2182 RT
  • A3 – within geostationary satellite range – all areas between latitudes 70′ N and 70′ S
  • As above plus HF DSC/RT or satellite
  • A4 – Other areas, beyond satellite range / within HF range, outside of satellite range


ZSC is an A3/A4 Coast Radio Station – we intend within the next year or two to renew our infrastructure and to implement area A1 VHF DSC Ch70 – we intend also to terminate the MF RT service and we are already broadcasting a notice to mariners that we do intend terminating our existing commercial services on radio telephony at the end of this month. This will not impact at all, on the SOLAS/GMDSS service that we do provide – important communications requests will be entertained – the only thing that will change, once these changes are in place, is that the billing or charging process will be eliminated. We will now concentrate our efforts and service on the safety of life and on other maritime assistance services [vessels seeking shelter from bad weather, vessels not under command, vessels having medical emergencies onboard, et cetera], and although we will be moving away from providing a public correspondence -happy birthday- commercial service, we will certainly continue to coordinate good communications during any given yacht race.

Communication is the exchange of information between individuals by means of speaking, writing, or using a common system of signs or behaviour. Although we are a maritime coast radio station, at the service of vessels at sea, our customers do also include: United Nations and Mercy Flight Aircraft, Air Force and Private helicopters, missionaries in distant countries and a variation of what we call special clients – although satellite communications have for the most part replaced previously used methods of communication, we do provide backup watch standing on RT, for the folks at Marion, Gough, St Helena and Tristan da Cunha Islands and for those at the S.A. National Antarctic Expedition near the South Pole.

The NAVAREA, coordinator must have: the expertise and information sources of a well established hydrographic service; he must have effective communications with Sub-Area and National coordinators within the NAVAREA, with other area coordinators, and with other data providers. He must have access to broadcast systems for transmission to the navigable waters of the particular area and he must endeavour to be informed of all events that could significantly affect the safety of navigation within the area. He must assess information upon receipt for relevance to navigation and he must select information and draft warnings for broadcast in accordance with guidance given by the IMO/IHO/WMO

NAVAREA warning/CNW/Local warning defined:

  • A NAVAREA warning is a long range, usually long term warning.
  • A coastal navigational warning is a temporary warning concerning something coastal.
  • A local warning normally concerns something inside of the fairway buoy of a given port.

NAVAREA VII WARNINGS are transmitted by ZSC as SATCOM or Inmrsat C SafetyNET messages, on receipt and are repeated at 0940 and 1940 UTC for 42 days, unless cancelled.

NAVTEX means the system for the broadcast and automatic reception of maritime safety information by means of narrow-band direct-printing telegraphy. It is a technique used to transmit coastal navigational warnings and weather forecasts by designated coast radio stations, [Cape Town, Port Elizabeth and Durban Radio] in the English language and on 518 kHz, during [IMO allocated] 10-minute time slots. This system is used on a time sharing basis coordinated by the International Maritime Organization – This is a one-way communication system, from coast radio stations to ships at sea. It has a range of about 200 nautical miles.  The Transmitter Identification Character [B1] is a single letter which is allocated to each transmitter. It is used to identify the broadcasting station – The Subject Indicator Character [B2] is used by the NAVTEX receiver to identify different classes of message and this character is used to reject certain optional subjects which are not required by the ship. In the NAVTEX receiver configuration, one has an option to select the Transmitter Identification Characters of station broadcasts which will be of interest and importance to you during your intended voyage and in so doing you will not receive broadcasts from stations that you have not selected in your choice of TIC

The ability to receive SafetyNET service information will be generally necessary for all ships which sail beyond coverage of NAVTEX.  Cape Town Radio compiles, prepares and initiates Enhanced Group Call [EGC] transmissions on SafetyNET, addressing the high seas Indian Ocean Region and the Atlantic Ocean Region East twice daily.

[Longitude 20E separates the two oceans]

COSPAS-SARSAT – The basic concept is: Beacon/satellite/Local User Terminal/Mission Control Centre/Rescue Coordination Centre /Search & Rescue unit:

Low-earth, near-polar, sun-synchronous, Medium-earth and Geostationary orbiting satellites search the earth for active 406 MHz emergency beacons from aviation, maritime and terrestrial carriers in distress. Satellite downlink signals are converted at the Local User Terminal [LUT], and fed to the Mission Control Centre [MCC] where the Cape Town Radio Operator validates beacon information, matches position, resolves ambiguity and alerts the relevant aeronautical or maritime rescue coordination centre so that a rescue may be launched.  The ASMCC is the single point of contact and responsibility for any distress alerts originating within NAVAREA VII and is the single point of contact for distress alerts originating from beacons encoded with the country codes [Angola, Botswana, Burundi, D.R.C, Lesotho, Malawi, Mozambique, Namibia, Rwanda, South Africa, St Helena Island, Swaziland, Uganda, Zambia and Zimbabwe] detected anywhere in the world.

The official 406 MHz beacon database custodians are the CAA and the MRCC – ultimately though, because we at the ASMCC make all associated beacon detection and we only are alerted by other MCCs worldwide to such beacon detection, the ASMCC must hold all such beacon registration information. We must be able to identify the beacon carrier and as such we must have registered owner / operator / boat / aircraft contact details. If a transmitting beacon is not registered, a search will not be conducted unless we receive an alert from an additional source. 20% of operationally programmed beacons, out of a total of >1.2 million emergency beacons are not registered. SAMSA MN# 22 of 2011 reminds mariners of the importance of proper beacon programming, proper beacon registration and proper corrections to such registration when changed ownerships occur.

The 406 MHz emergency position indicating radio beacon identity consists of 15 hexadecimal characters made up from a combination of letters and numerals A to F and 0 to 9 The encoding process is decoded to prove proper coding and ultimately to accomplish proper registration at the ASMCC.

POLICY ON 406 MHZ BEACON TESTING – Don’t, unless this is conducted inside a Faraday Cage: [a container giving protection from electrical fields: an assembly of conducting material, for example, metal mesh, placed around electrical equipment to protect it from external electrical fields]

The COSPAS-SARSAT Mission Control Centre considers the following factors: Match on frequency; Match on sweep period and detection within a certain distance of each other. All three parameters have certain thresholds for matching and provided that the detection is within these thresholds then a match can be made. It is for this reason, that sometimes an Operator can make an informed judgment decision, whereas software, configured to certain parameters, does not.

THE LEOSAR SYSTEM consists of satellites that orbit the poles at a speed of 7km/second ??? these satellites are enabled to determine the position of the beacon by means of the Doppler Effect: [Change in frequency because of motion: a perceived change in the frequency of a wave as the distance between the source and the observer changes. For example, the sound of a siren on a moving vehicle appears to change as it approaches and passes an observer.]


The GEOSAR space segment is composed of geostationary satellites with the capability to relay the transmissions of COSPAS-SARSAT 406 MHz beacons. Geostationary satellites orbit at an altitude of 36,000 km, with an orbit period of 24 hours, thus appearing fixed relative to the Earth, at approximately 0 degrees latitude [i.e. over the Equator]. These satellites provide continuous global coverage with the exception of the polar-regions. A single geostationary satellite provides GEOSAR uplink coverage of about one third of the globe, except for polar-regions. Therefore, three geostationary satellites equally spaced in longitude can provide continuous coverage of all areas of the globe between approximately 70?? North and 70?? South.


Part of this medium earth orbit system is already in place and part thereof is still under development and it is expected to be fully operational by 2018. Three constellations of American, European and Russian satellites will orbit at 19000-24000 km ??? one system complimenting the other – the concept is that two satellites at least will have a view of any transmitting beacon, at any given time and the added benefit is that ground segment operators will be enabled to send reply messages to the transmitting instrument.


This technique uses digital codes to enable a radio station to establish contact with and to transfer information to another station. Cape Town Radio [Maritime Mobile Service Identity: 006010001] guards HF DSC on 4, 6, 8, 12 and 16 MHz – Subsequent communications succeeding an initial DSC alert is conducted on radio telephony.

Soon to be introduced is DSC on VHF Ch70 at sites around the South African coast.

The Automated Mutual-assistance VEssel Rescue (AMVER) System, operated by the United States Coast Guard, is an organization that provides important aid to the development and co-ordination of Search and Rescue efforts in many areas of the world. Merchant vessels of all nations making offshore voyages are encouraged to send movement reports and periodic position reports to AMVER through selected Coast Radio Stations’ information from these reports are computed to maintain dead reckoning positions for vessels while they are within the plotting area  characteristics of vessels that are valuable for determining SAR capability are computed from available sources – information concerning predicted location and SAR characteristics of each vessel known to be within the area of interest, is made available to SAR agencies of any nation. Similarly in South Africa and in the interests of safety, ships are encouraged to participate in the voluntary South African Ship Reporting [SAFREP] system – This system assists in search and rescue by providing up-to-date shipping information in the event of a maritime casualty. It is “modeled” on IMO Resolution A851 regarding general principles for ship reporting requirements and makes use of movement reports, submitted by ships within the SASAR region to Cape Town Radio. SAFREPs are processed and fed to maritime intelligence, they are made available for MRCC search and rescue use and valuable weather information within these reports is fed to the South African Weather Service.

Piracy Attacks and the Ship Security Alerting System

Special signals have been developed for use by ships under attack or threat of attack from pirates or armed robbers. “Piracy/armed robbery attack” is a category of distress message for all classes of digital selective call and Inmarsat-C equipment. For their own safety, ships may have to covertly send out the “piracy/armed robbery attack” message. When the RCC becomes aware of such a situation, it declares the Alert Phase, advises appropriate response agencies as specified in the plans of operation, and begins preparations for possible SAR operations as appropriate. If the ship covertly sends a message, care must be used in any communications sent back to the ship so as not to warn the pirates. The International Piracy Reporting Centre in Kuala Lumpur broadcasts warnings concerning known danger areas, via the SafetyNET system. A ship under threat in South African territorial waters or in a South African port may communicate with the local Port Control, Port Security Officer, the MRCC or Cape Town Radio. Such alerts are routed to the relevant competent authority.

The Melkbos Submarine Cable Station – Three high capacity fibre optic telecommunications cables, link Southern Africa, Western Africa, Europe and the Far East, providing telephone, data, Internet and television services.

On the West Coast: Melkbos Strand, Angola, Gabon, Cameroon, Nigeria, Benin, Ghana, Ivory Coast, Senegal, Altavista/Spain [Funchal, Elmedano] Spain and Portugal.

On the East Coast: Melkbos Strand, Mtunzini, Reunion, Mauritius, India, Malaysia.

A computerized radar surveillance system at Melkbos monitors shipping anywhere close to the cable or cable landings – Cape Town Radio is called upon to establish contact with and to instruct vessels to safely relocate without causing damage to their person or to the cable.


The word tsunami originates from the Japanese [tsu, harbour and nami, waves]

An enormous sea wave, caused by the sudden large-scale movement of the sea floor, resulting in the displacement of large volumes of water – the cause may be an earthquake, volcanic eruption, a submarine slide or slump of sediment, which may itself have been started by an earthquake or tremor – the slipping of thousands of tonnes of rock from the sides of Fjords may also cause tsunami – the effect of this sea floor movement in the open ocean may not be seen at all, as the resulting wave may only be one metre or less in height – however, because the whole depth of water is affected, there is a vast amount of energy involved and so when the waves reach shallow water or small bays, the effects can be catastrophic. Negative tidal surge and tsunami warnings will normally be the subject of navigational warnings issued by the HYDROGRAPHER and will be broadcast on all voice, digital and satellite systems by Cape Town Radio, on receipt and with every scheduled transmission until the “degree of hazard” diminishes in intensity and ceases.


Cape Town Radio is the first point of contact for ISPS Pre-arrival-report submissions – we process these messages and forward to the MRCC in Cape Town, who in turn share with the Maritime Security Co-ordination Centre in Pretoria who either approve or deny the ship entry into port – this decision is relayed to the vessel via the relevant Port Security Officer.

FREE MEDICAL ADVICE: In South Africa, medical advice is free of charge to the mariner – The Cape Town Radio Operator connects the METRO doctor to the vessel seeking diagnosis and advice MRCC decisions to evacuate patients by helicopter or launch, [sooner than when the ship will normally arrive in port], are based on the recommendations of the METRO doctor. All associated correspondence and communication is affected via ZSC.

OBS and the World Meteorological Organization Voluntary Observing Ship Program:

Weather forecasting, operational planning for maritime activities, the design of vessels and coastal and offshore facilities, the exploitation of marine and sea-bed resources, the response to oil spills at sea and climate research all require a knowledge of weather conditions over the oceans.  Mariners face many hazards storms, rough seas, ice and icebergs  this reality led seafaring nations to organize the first formal international meteorological meeting in 1853 to coordinate weather observing at sea.

Observations from VOS significantly complement the bird’s eye view of the global distribution of clouds, weather systems and ocean variables obtained from satellites. They provide information on phenomena that cannot be accurately, reliably and consistently observed from space. The most critical variable is surface air pressure.  The observations from VOS continue to provide essential inputs to operational weather forecasting, supply ground truth measurements for calibration of satellite readings, add to our growing knowledge of ocean climates, increase our understanding of the linkages between the oceans and the atmosphere and contribute to the development of important historical databases.

The advent of the age of the weather satellite has in no way diminished the importance of reports from VOS – these reports are submitted via ZSC to the SAWS – ultimately, your weather observation submissions do assist the forecaster to better predict your weather.

PORTHEALTH QUARANTINE REPORTS – A request for free pratique is a request for permission to use a port – permission is granted to a ship to use a port, if she has satisfied local quarantine regulations and has produced a clean bill of health. Radio quarantine reports from vessels seeking health clearance are fed via Cape Town Radio to the relevant port health officer who either grants free pratique or withholds pratique pending boarding on arrival

As technology has advanced over the years, so too has the use of Radio Telephony lessened. In many cases, satellite telephony and e-mails have replaced the HF SSB radio entirely and for commercial purpose, this is neither here nor there whereas for distress purposes, there is a challenge. Some folks favour radio whilst others do not. The reality is that if in any form of difficulty, one chooses to use a satellite or cellular telephone or to send an e-mail to a single address then in most cases, you are only alerting one person.  If you alert a Coast Radio Station, using any mean

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