History
Special Topic Report - Stockholmradio /SDJ
1. Historical perspective
The history of coast radio services in the Stockholm area dates back to 1902 when a Royal Swedish Navy experimental coast radio station was built at the Waxholm fortress at the entrance to Stockholm from the Baltic Sea. This first station in 1914 became a public correspondence station as a joint venture between the Navy and the Royal Swedish Telecommunications Board, and was upgraded to use a Telefunken "Tonende Funken" 8 kW spark transmitter.
In the 1920's, the station's services were supplemented by radiotelephony and CW telegraphy, and the Navy operational engagement ended due to disputes about funding and management.
The station resided at the fortress until 1937, when a new station, optimized for MF radiotelegraphy and telephony, was built in the small archipelago village Stavsnas, about 40 km due east of the Stockholm City centre. A new separate transmitter site was founded at the shore, and the operational centre and receiving site was located in the rented top floor of a small villa in the heart of the village. Operation in these quite cramped and uncomfortable quarters continued through the war years, with a sometimes high workload due to the wartime dangers for shipping and refugee traffic in the Baltic.
In 1947, a new operational and receiver building was built at the outskirt of the village, in a "prestige" location with a breathtaking view of the archipelago.
Also in 1947 the roles of the civilian coast radio stations in the Swedish Search and Rescue system were formalized, and Stockholmradio became the appointed Maritime Rescue Coordination Centre (MRCC) for the Swedish territorial waters of the Baltic Sea.
The years to come witnessed great changes; MF gradually lost its once major role, and was replaced by VHF for volume traffic. In 1973, a major reorganization of the network was commenced, closing the smaller MF only stations and concentrating the VHF and MF services to the remaining three stations Goteborg Radio in the west, Stockholm Radio in the east and Harnosand Radio in the north, all three also being MRCCs.
As part of an organizational structure change in 1979, Stockholmradio moved from its scenic site in "splendid isolation" in the archipelago to the top floor of the Telecom Administration regional office building in a southern Stockholm urban industrial district.
This move was also a part of a merger of the services of the HF Air/Ground and point-to-point station Enkoping Radio. The moving and merging operations were completed in 1980, and VHF services for the merchant shipping and the pleasure boaters in the dense archipelago became the station's main business, together with the MRCC role and the Air/Ground services.
The 1980s also became a decade of change, the once profitable VHF services became faced with the mass market mobile telephony competition, and were reduced to a fraction at the end of the decade. This reduction was to some extent offset by an increase of the MRCC and Air/Ground activities.
The first years of the 1990's also brought changes of completely unexpected magnitude and rate. It all started by a seemingly innocent statement in the fine print of a 1992 Maritime Administration study paper that the MRCC structure was to be scrutinized, and that the new structure by all probability had no place for Harnosand Radio, the northernmost station. The management reacted quickly by assigning the staff of Harnosand Radio to other job positions, and launching a crash project for remote control from Stockholmradio, effective March 31, 1993. This was followed only a few months later by another decision to redesign and upgrade the two remaining stations, using off-the-shelf commercial hardware and software products, into a new and more flexible architecture.
Only a few months into this project, the Maritime Administration, responsible for the MRCC funding, declared their decision to operate the Goteborg MRCC under their own regime, and that any involvement with commercial coast radio was neither wanted nor necessary. Again, the management reacted without delay, declaring that the remaining MF, HF and VHF manual services of Goteborg Radio were to be immediately closed and transferred to Stockholmradio, as soon as the new switching infrastructure was delivered and installed. This was completed in the autumn of 1994 and only weeks later the Goteborg Radio coast radio service was history.
As part of this project, the Stockholmradio operational centre moved again, this time to brand new premises about 10 km due east from the city centre, occupying a top office floor overlooking the entrance to the Stockholm harbour.
Currently, Stockholmradio is the sole commercial coast radio station in Sweden, as the naval coast stations Karlskrona Radio (SAA) and Tingstade Radio (SAE) no longer provide telegram services operated on MF and HF telegraphy and MF telephony.
It is quite safe to say that many people, inside as well as outside of the coast radio services in Sweden, were taken by surprise by the outcome of the turbulence in the 1992 - 1994 period. As late as 1990, it would have been considered quite safe and unimaginative to bet money on the assumption that Goteborg Radio would be the remaining coast station in Sweden, by virtue of its size and the massive investments made there in the 1970's and 80's. On the contrary, it turned out that its size was to be a major drawback in terms of operating costs, and that the investments were aimed at optimizing traffic capacity for services that were no longer required. It is maybe appropriate to consider the fate of Goteborg Radio as a striking illustration of the dangers associated with resting on old laurels.
In late 2002 it became evident that the Telia Mobile organization no longer wanted to operate a coast radio service. Negotiations with different parties resulted in the operational services being transferred to the Viamare group, the technical operations to the Telemar Scandinavia AB group, and the coastal radio network itself was purchased by the Maritime Adminstration. All these changes became effective May 1, 2003.
The changed ownership necessitated one more move for Stockholm Radio, this time to a neighbouring block at Nacka Strand. This means that Stockholm Radio has moved a total of five times in its lifetime, probably a world record. Usually the move of a coast radio station implies it may soon end up at the scrap heap but not Stockholm Radio.
Selling off the Stavsnäs site made it necessary to implement a replacement site somewhere in the central Baltic. The choice became the old Naval site on the island of Gotland, where the Maritime Administration rents space for transmitters and access to antennas.
In the 1920's, the station's services were supplemented by radiotelephony and CW telegraphy, and the Navy operational engagement ended due to disputes about funding and management.
The station resided at the fortress until 1937, when a new station, optimized for MF radiotelegraphy and telephony, was built in the small archipelago village Stavsnas, about 40 km due east of the Stockholm City centre. A new separate transmitter site was founded at the shore, and the operational centre and receiving site was located in the rented top floor of a small villa in the heart of the village. Operation in these quite cramped and uncomfortable quarters continued through the war years, with a sometimes high workload due to the wartime dangers for shipping and refugee traffic in the Baltic.
Also in 1947 the roles of the civilian coast radio stations in the Swedish Search and Rescue system were formalized, and Stockholmradio became the appointed Maritime Rescue Coordination Centre (MRCC) for the Swedish territorial waters of the Baltic Sea.
The years to come witnessed great changes; MF gradually lost its once major role, and was replaced by VHF for volume traffic. In 1973, a major reorganization of the network was commenced, closing the smaller MF only stations and concentrating the VHF and MF services to the remaining three stations Goteborg Radio in the west, Stockholm Radio in the east and Harnosand Radio in the north, all three also being MRCCs.
As part of an organizational structure change in 1979, Stockholmradio moved from its scenic site in "splendid isolation" in the archipelago to the top floor of the Telecom Administration regional office building in a southern Stockholm urban industrial district.
This move was also a part of a merger of the services of the HF Air/Ground and point-to-point station Enkoping Radio. The moving and merging operations were completed in 1980, and VHF services for the merchant shipping and the pleasure boaters in the dense archipelago became the station's main business, together with the MRCC role and the Air/Ground services.
The 1980s also became a decade of change, the once profitable VHF services became faced with the mass market mobile telephony competition, and were reduced to a fraction at the end of the decade. This reduction was to some extent offset by an increase of the MRCC and Air/Ground activities.
The first years of the 1990's also brought changes of completely unexpected magnitude and rate. It all started by a seemingly innocent statement in the fine print of a 1992 Maritime Administration study paper that the MRCC structure was to be scrutinized, and that the new structure by all probability had no place for Harnosand Radio, the northernmost station. The management reacted quickly by assigning the staff of Harnosand Radio to other job positions, and launching a crash project for remote control from Stockholmradio, effective March 31, 1993. This was followed only a few months later by another decision to redesign and upgrade the two remaining stations, using off-the-shelf commercial hardware and software products, into a new and more flexible architecture.
Only a few months into this project, the Maritime Administration, responsible for the MRCC funding, declared their decision to operate the Goteborg MRCC under their own regime, and that any involvement with commercial coast radio was neither wanted nor necessary. Again, the management reacted without delay, declaring that the remaining MF, HF and VHF manual services of Goteborg Radio were to be immediately closed and transferred to Stockholmradio, as soon as the new switching infrastructure was delivered and installed. This was completed in the autumn of 1994 and only weeks later the Goteborg Radio coast radio service was history.
As part of this project, the Stockholmradio operational centre moved again, this time to brand new premises about 10 km due east from the city centre, occupying a top office floor overlooking the entrance to the Stockholm harbour.
Currently, Stockholmradio is the sole commercial coast radio station in Sweden, as the naval coast stations Karlskrona Radio (SAA) and Tingstade Radio (SAE) no longer provide telegram services operated on MF and HF telegraphy and MF telephony.
It is quite safe to say that many people, inside as well as outside of the coast radio services in Sweden, were taken by surprise by the outcome of the turbulence in the 1992 - 1994 period. As late as 1990, it would have been considered quite safe and unimaginative to bet money on the assumption that Goteborg Radio would be the remaining coast station in Sweden, by virtue of its size and the massive investments made there in the 1970's and 80's. On the contrary, it turned out that its size was to be a major drawback in terms of operating costs, and that the investments were aimed at optimizing traffic capacity for services that were no longer required. It is maybe appropriate to consider the fate of Goteborg Radio as a striking illustration of the dangers associated with resting on old laurels.
In late 2002 it became evident that the Telia Mobile organization no longer wanted to operate a coast radio service. Negotiations with different parties resulted in the operational services being transferred to the Viamare group, the technical operations to the Telemar Scandinavia AB group, and the coastal radio network itself was purchased by the Maritime Adminstration. All these changes became effective May 1, 2003.
The changed ownership necessitated one more move for Stockholm Radio, this time to a neighbouring block at Nacka Strand. This means that Stockholm Radio has moved a total of five times in its lifetime, probably a world record. Usually the move of a coast radio station implies it may soon end up at the scrap heap but not Stockholm Radio.
Selling off the Stavsnäs site made it necessary to implement a replacement site somewhere in the central Baltic. The choice became the old Naval site on the island of Gotland, where the Maritime Administration rents space for transmitters and access to antennas.
2. Services
Stockholmradio has quite a unique station architecture providing many types of different services, all sharing a common technical infrastructure and personnel.
About 20 people are employed in the operations, and a typical day shift has about 3 - 4 staff members, compared to 2 for a night shift.
2.1 Maritime safety services
Effective October 1, 2002 the MRSC (Maritime Rescue Sub-Center) function is no longer effectuated from Stockholm Radio, as the Maritime Administration decided to close all MRSCs.
Stockholmradio is still the technical centre for the VHF-DSC (Channel 70) and MF-DSC (2187.5 kHz) distress monitoring systems.
Additionally, all transmissions of navigational warnings, weather reports and other maritime safety information on telephony or NAVTEX are made from Stockholmradio which also performs the Swedish NAVAREA information coordinating and distribution functions of the Baltic Coordinator “Baltico” outside office hours.
2.2 Maritime commercial services
Stockholmradio still provides the usual coast radio commercial services with the exception of MF and HF morse telegraphy.
Services are:
· MF telephony services
· Channel 16 watchkeeping
· VHF telephony services
· HF telephony services ("Seaphone")
The service area for the maritime commercial services are all Swedish coastal waters, adding HF coverage of the Atlantic, the Indian Ocean and the Mediterranean Sea. Other commercial undertakings are the technical service provisions for harbour traffic control and pilotage control services.
Service volumes have slowly but steadily declined since the 1980's, with the exception of the MF telegraphy, which due to the lifting of the Iron Curtain and the increase of Russian Federation foreign trade via Baltic ports, actually saw an increase in 1991 - 1995, up to a daily average of about 40 telegrams. At the time of the final closure for MF telegraphy in 2002, the traffic volume was down to a telegram or two every other month.
The annual VHF traffic is very unevenly distributed with a peak period of about 50 – 100 calls per day for a few weeks during the summer holidays otherwise the traffic falls to a fairly constant level of about 10 - 20 calls per day.
2.3 Air/Ground services
The Air/Ground services are aimed at the airline market and provide HF equipped aircraft with a means to keep in contact with their ground based company offices via the telephone network or by either AFTN/SITA messages.
Services of this type have been provided in Sweden since 1967, initially from the HF station Enkoping Radio, but since 1980 from Stockholm Radio where currently a customer base of about 300 aircraft operators engage regularly.
About 20 people are employed in the operations, and a typical day shift has about 3 - 4 staff members, compared to 2 for a night shift.
2.1 Maritime safety services
Effective October 1, 2002 the MRSC (Maritime Rescue Sub-Center) function is no longer effectuated from Stockholm Radio, as the Maritime Administration decided to close all MRSCs.
Stockholmradio is still the technical centre for the VHF-DSC (Channel 70) and MF-DSC (2187.5 kHz) distress monitoring systems.
Additionally, all transmissions of navigational warnings, weather reports and other maritime safety information on telephony or NAVTEX are made from Stockholmradio which also performs the Swedish NAVAREA information coordinating and distribution functions of the Baltic Coordinator “Baltico” outside office hours.
2.2 Maritime commercial services
Stockholmradio still provides the usual coast radio commercial services with the exception of MF and HF morse telegraphy.
Services are:
· MF telephony services
· Channel 16 watchkeeping
· VHF telephony services
· HF telephony services ("Seaphone")
The service area for the maritime commercial services are all Swedish coastal waters, adding HF coverage of the Atlantic, the Indian Ocean and the Mediterranean Sea. Other commercial undertakings are the technical service provisions for harbour traffic control and pilotage control services.
Service volumes have slowly but steadily declined since the 1980's, with the exception of the MF telegraphy, which due to the lifting of the Iron Curtain and the increase of Russian Federation foreign trade via Baltic ports, actually saw an increase in 1991 - 1995, up to a daily average of about 40 telegrams. At the time of the final closure for MF telegraphy in 2002, the traffic volume was down to a telegram or two every other month.
The annual VHF traffic is very unevenly distributed with a peak period of about 50 – 100 calls per day for a few weeks during the summer holidays otherwise the traffic falls to a fairly constant level of about 10 - 20 calls per day.
2.3 Air/Ground services
The Air/Ground services are aimed at the airline market and provide HF equipped aircraft with a means to keep in contact with their ground based company offices via the telephone network or by either AFTN/SITA messages.
Services of this type have been provided in Sweden since 1967, initially from the HF station Enkoping Radio, but since 1980 from Stockholm Radio where currently a customer base of about 300 aircraft operators engage regularly.
3. System architecture
The nucleus of the system is the switching centre, using a GAREX 220 Voice Communications and Control Switch (VCCS). The GAREX 220 is a computer controlled switching system manufactured by Park Air Systems A/S in Norway, and originally designed for Air Traffic Control centre purposes. See GAREX 220 for more details.
Other GAREX installations for coast radio can be found in China, Estonia, Iceland, Singapore, Taiwan, Turkey and the United Arab Emirates.
All switching and control functions in the system are made in the VCCS.
Two types of operation consoles exist, one which is X-terminal Graphical User Interface (GUI) based, and one which uses conventional lighted function buttons. The GUI based consoles are connected to two UNIX servers per VCCS via an Ethernet LAN, and the function-button based consoles, which can either be locally or remotely operated, are directly interfaced to the VCCS.
3.1 Coast radio function
The coast radio function is centred around the Traffic Central where a continuous watch is maintained on the distress and calling channels. Staff at the Traffic Central also handle the call bookings by telephone subscribers and other general customer service enquiries.
At night-time, and in off-peak seasons, the VHF and MF duplex working channels are also operated from this area. The Traffic Central itself has 4 operating consoles. One more supplementary console for weather and navigational warning broadcasts is also part of the Traffic Central.
One X-terminal (GUI) based operator console has a design watch keeping capacity limit of 120 channels, which never is approached in practice. A more realistic distribution limit is about 35 - 50 channels per console. Each console has up to 6 loudspeakers, to which suitable selections and combinations of channels can be directed.
There are no radio panels or conventional-looking remote control facilities whatsoever in the coast station system, X-terminal workstations and "dumb terminals" are used for all phases of system control and message handling.
3.1.1 Coast Radio Network
The network used is primarily composed of VHF base stations sited in as tall structures as possible. On the Baltic Coast extensive use has been made of the FM/TV broadcast towers, in which the VHF antennas usually are mounted at more than 300 meters above sea level. On the west coast, where the depth of the required coverage area is less, lower masts for 900 MHz mobile telephone sites are used. The total number of VHF sites is 55, with a total number of some 250 radio channels, simplex and duplex.
As far as we know, this is the largest contiguous maritime radio network in the world.
A base station consists of one transceiver for channel 16, one for channel 70, one or more for port operations simplex channels and at least one more for the duplex working channels.
The transceivers used are general purpose solid-state VHF/FM types.
The MF network uses all remotely controlled receivers and transmitters, at sites around the coast:
Bjuröklubb; 64 28.0 N, 21 36.0 E 518, 2182, 2187.5, 1779 kHz
Harnösand Hemsö; 62 42.3 N, 18 07.5 E , 2182, 2187.5, 2733 kHz
Tingstäde Gotland; 57 43.3 N, 18 35.1 E 518, 2182, 2187.5, 1674 kHz
Gislövshammar; 55 29.2 N, 14 19.0 E 518, 2182, 2187.5,1797 kHz
Grimeton; 57 10.2 N, 12 20.1 E 518, 2182, 2187.5, 1710 kHz
All general purpose MF telephony transmitters are Standard Radio SST490 0.8 kW solid-state SSB/ISB types feeding vertical resonant or broadband radiators. The remote controlled general purpose receivers are Standard Radio CR300 and CR91 types. Skanti R-5000/R-5001s are used for watch keeping channels.
For MF telegraphy and NAVTEX dual Nautel 1 kW solid-state FSK transmitters are used at each site.
Pictures of some Stockholm Radio MF infrastructure are depicted on Robert Maskill’s Coastal Radio pages.
3.1.2 Radio infrastructure services
For many years, the performance of the purpose-built radio networks used by for example port operations, icebreaking and traffic control services have been found to be lacking in capacity and in coverage area. Envious remarks had been made about the high performance of the coast radio VHF system for years and when the new VCCS system was installed in 1994, with its inherent capability for "remote operator consoles", the Oxelosund (80 km SW from Stockholm) port operations radio system was replaced with a connection to the Stockholmradio technical infrastructure, as a trial project, sharing channel 16 and a handful of duplex channels, and operating two dedicated simplex channels.
The improvements in operational quality and coverage were dramatic and today 11 more pilot and port operations radio systems are connected into the system. The gains attained have been twofold, firstly the high-performance channel 16 and duplex installations are better utilized, and secondly a smaller number of dedicated channels are required to cover a given area, as the offered antenna height is much greater than in previous systems.
Even though the Göteborg MRCC is operated and staffed by the Maritime Administration, and not co-located with any coast station, it uses the same systems architecture and radio network. The Göteborg MRCC has several operating positions connected to the VCCS system by means of a fibre-optic data and telephony trunk.
Use of the Stockholmradio technical infrastructure is also made for the new Automatic Identifications System (AIS) VHF transponder base network, which is used to track the movements of AIS transponder equipped vessels in real-time. A mesh-shaped data network connects the individual transponders to a regional server for distribution of the collected AIS data to subscribers.
The AIS system makes use of the novel Self-organizing Time Division Multiple Access (STDMA) scheme devised by the Swedish inventor Hakan Lans.
More about the STDMA datalinks can be read on the GP&C homepage.
3.2 MRSC function
The Stockholm MRSC is a subset of the operational functions of the whole network, concentrated into two operating positions. From each workstation, the MRSC officers have access to all communications facilities, radio and landline, in the entire network. These facilities can be combined and used at will, providing the Search and Rescue Coordinating officer with a powerful communications, command and control tool.
3.3 Air/Ground radio function
In the Air/Ground radio function, no distinctions are made between the calling and traffic channels, so no traffic central exists. 6 primary or calling channels are loudspeaker monitored in the system, at up to 4 operating consoles.
Primary frequencies are:
3494 kHz (22 - 05 UTC)
5541 kHz (H24)
8930 kHz (H24)
11345 kHz (H24)
13342 kHz (H24)
17916 kHz (H24)
23210 kHz (05 - 22 UTC)
The operator consoles were originally designed to work into the relay-logic based HF traffic system at the previous location of the station, and as the relocation project progressed, it was felt that they were too valuable to be scrapped. A decision was made to design an interface adapter enabling them to be used in the VCCS system as ordinary function-button based operator consoles.
The Air/Ground operators are able to select any of 16 receivers, 10 transmitters and 8 landlines, as well as the SELCAL generator and have access to computer data banks for airport weather information, customer data and message handling.
3.3.1 Air/Ground HF Radio Network
The HF network, like the VHF and MF networks, uses remotely controlled receivers and transmitters. The transmitters are situated at Karlsborg in western Sweden, built in the 1920's for LF point-to-point traffic.
A large number of HF transmitters were installed at Karlsborg in the mid-1960's, to cater for an anticipated increase in HF point-to-point traffic which never occurred. Instead, the site and equipment became primarily used for mobile HF services.
The aeronautical services have access to a total of 10 HF/SSB transmitters from Rockwell/Collins with power outputs of 10 and 3 kW, feeding log-periodic, dipole and rhombic radiators.
Receivers, of the Standard Radio CR300, CR91 and ICOM IC-R71 types, are installed at the Enkoping station, and also at the old Goteborg Radio receiving site as well as those at other MF receive sites along the coast. The antenna system employed is a mixture of TCI horizontal and vertical log-periodic arrays, together with dipoles and vertical omni antennas.
Other GAREX installations for coast radio can be found in China, Estonia, Iceland, Singapore, Taiwan, Turkey and the United Arab Emirates.
All switching and control functions in the system are made in the VCCS.
Two types of operation consoles exist, one which is X-terminal Graphical User Interface (GUI) based, and one which uses conventional lighted function buttons. The GUI based consoles are connected to two UNIX servers per VCCS via an Ethernet LAN, and the function-button based consoles, which can either be locally or remotely operated, are directly interfaced to the VCCS.
3.1 Coast radio function
The coast radio function is centred around the Traffic Central where a continuous watch is maintained on the distress and calling channels. Staff at the Traffic Central also handle the call bookings by telephone subscribers and other general customer service enquiries.
At night-time, and in off-peak seasons, the VHF and MF duplex working channels are also operated from this area. The Traffic Central itself has 4 operating consoles. One more supplementary console for weather and navigational warning broadcasts is also part of the Traffic Central.
One X-terminal (GUI) based operator console has a design watch keeping capacity limit of 120 channels, which never is approached in practice. A more realistic distribution limit is about 35 - 50 channels per console. Each console has up to 6 loudspeakers, to which suitable selections and combinations of channels can be directed.
There are no radio panels or conventional-looking remote control facilities whatsoever in the coast station system, X-terminal workstations and "dumb terminals" are used for all phases of system control and message handling.
3.1.1 Coast Radio Network
The network used is primarily composed of VHF base stations sited in as tall structures as possible. On the Baltic Coast extensive use has been made of the FM/TV broadcast towers, in which the VHF antennas usually are mounted at more than 300 meters above sea level. On the west coast, where the depth of the required coverage area is less, lower masts for 900 MHz mobile telephone sites are used. The total number of VHF sites is 55, with a total number of some 250 radio channels, simplex and duplex.
As far as we know, this is the largest contiguous maritime radio network in the world.
A base station consists of one transceiver for channel 16, one for channel 70, one or more for port operations simplex channels and at least one more for the duplex working channels.
The transceivers used are general purpose solid-state VHF/FM types.
The MF network uses all remotely controlled receivers and transmitters, at sites around the coast:
Bjuröklubb; 64 28.0 N, 21 36.0 E 518, 2182, 2187.5, 1779 kHz
Harnösand Hemsö; 62 42.3 N, 18 07.5 E , 2182, 2187.5, 2733 kHz
Tingstäde Gotland; 57 43.3 N, 18 35.1 E 518, 2182, 2187.5, 1674 kHz
Gislövshammar; 55 29.2 N, 14 19.0 E 518, 2182, 2187.5,1797 kHz
Grimeton; 57 10.2 N, 12 20.1 E 518, 2182, 2187.5, 1710 kHz
All general purpose MF telephony transmitters are Standard Radio SST490 0.8 kW solid-state SSB/ISB types feeding vertical resonant or broadband radiators. The remote controlled general purpose receivers are Standard Radio CR300 and CR91 types. Skanti R-5000/R-5001s are used for watch keeping channels.
For MF telegraphy and NAVTEX dual Nautel 1 kW solid-state FSK transmitters are used at each site.
Pictures of some Stockholm Radio MF infrastructure are depicted on Robert Maskill’s Coastal Radio pages.
3.1.2 Radio infrastructure services
For many years, the performance of the purpose-built radio networks used by for example port operations, icebreaking and traffic control services have been found to be lacking in capacity and in coverage area. Envious remarks had been made about the high performance of the coast radio VHF system for years and when the new VCCS system was installed in 1994, with its inherent capability for "remote operator consoles", the Oxelosund (80 km SW from Stockholm) port operations radio system was replaced with a connection to the Stockholmradio technical infrastructure, as a trial project, sharing channel 16 and a handful of duplex channels, and operating two dedicated simplex channels.
The improvements in operational quality and coverage were dramatic and today 11 more pilot and port operations radio systems are connected into the system. The gains attained have been twofold, firstly the high-performance channel 16 and duplex installations are better utilized, and secondly a smaller number of dedicated channels are required to cover a given area, as the offered antenna height is much greater than in previous systems.
Even though the Göteborg MRCC is operated and staffed by the Maritime Administration, and not co-located with any coast station, it uses the same systems architecture and radio network. The Göteborg MRCC has several operating positions connected to the VCCS system by means of a fibre-optic data and telephony trunk.
Use of the Stockholmradio technical infrastructure is also made for the new Automatic Identifications System (AIS) VHF transponder base network, which is used to track the movements of AIS transponder equipped vessels in real-time. A mesh-shaped data network connects the individual transponders to a regional server for distribution of the collected AIS data to subscribers.
The AIS system makes use of the novel Self-organizing Time Division Multiple Access (STDMA) scheme devised by the Swedish inventor Hakan Lans.
More about the STDMA datalinks can be read on the GP&C homepage.
3.2 MRSC function
The Stockholm MRSC is a subset of the operational functions of the whole network, concentrated into two operating positions. From each workstation, the MRSC officers have access to all communications facilities, radio and landline, in the entire network. These facilities can be combined and used at will, providing the Search and Rescue Coordinating officer with a powerful communications, command and control tool.
3.3 Air/Ground radio function
In the Air/Ground radio function, no distinctions are made between the calling and traffic channels, so no traffic central exists. 6 primary or calling channels are loudspeaker monitored in the system, at up to 4 operating consoles.
Primary frequencies are:
3494 kHz (22 - 05 UTC)
5541 kHz (H24)
8930 kHz (H24)
11345 kHz (H24)
13342 kHz (H24)
17916 kHz (H24)
23210 kHz (05 - 22 UTC)
The operator consoles were originally designed to work into the relay-logic based HF traffic system at the previous location of the station, and as the relocation project progressed, it was felt that they were too valuable to be scrapped. A decision was made to design an interface adapter enabling them to be used in the VCCS system as ordinary function-button based operator consoles.
The Air/Ground operators are able to select any of 16 receivers, 10 transmitters and 8 landlines, as well as the SELCAL generator and have access to computer data banks for airport weather information, customer data and message handling.
3.3.1 Air/Ground HF Radio Network
The HF network, like the VHF and MF networks, uses remotely controlled receivers and transmitters. The transmitters are situated at Karlsborg in western Sweden, built in the 1920's for LF point-to-point traffic.
A large number of HF transmitters were installed at Karlsborg in the mid-1960's, to cater for an anticipated increase in HF point-to-point traffic which never occurred. Instead, the site and equipment became primarily used for mobile HF services.
The aeronautical services have access to a total of 10 HF/SSB transmitters from Rockwell/Collins with power outputs of 10 and 3 kW, feeding log-periodic, dipole and rhombic radiators.
Receivers, of the Standard Radio CR300, CR91 and ICOM IC-R71 types, are installed at the Enkoping station, and also at the old Goteborg Radio receiving site as well as those at other MF receive sites along the coast. The antenna system employed is a mixture of TCI horizontal and vertical log-periodic arrays, together with dipoles and vertical omni antennas.
4. Future of the Stockholmradio services
It has been said predicting the future has never been easy and Stockholmradio is no exception.
The commercial operations of the system have a combined traffic load of about 150,000 annual transactions, which generates sufficient revenues to keep the figures out of the red.
Presently, it appears that the Stockholmradio maritime services have a reasonably assured future for the next few years, as the Maritime Administration has agreed to a continued involvement in the maritime safety field. It is reasonable to expect that the flourishing mobile telephone market will further reduce traffic revenues from merchant shipping and boaters, maybe down to a level where the commercial aspects are neglected.
Finally the future of the Air/Ground HF voice services is very much linked to the rate of exchanging old aircraft for new.
Historically and by experience it has been found that the acquisition of new aircraft by an airline leads to the sale of the old to a more penny-pinching airline which usually don't want to make the investment in SATCOM and feels that HF has a satisfactory price/performance ratio for company communications. New aircraft on the other hand, are usually equipped with HF datalink, ACARS and SATCOM from the beginning.
Stockholmradio celebrated its 75th anniversary in 1989, and the possibilities that the station will be around in some form to celebrate its 100th anniversary have increased.
It can be appropriate in this context to quote an anecdote from the wireline telegraph days in the mid-19'th century, when a hurried customer rushed to the Stockholm Central telegraph office to hand in a telegram, asking the clerk at the counter when the office closes. The clerk responded:
"Close? We close earliest at doomsday, but quite late in the evening."
The commercial operations of the system have a combined traffic load of about 150,000 annual transactions, which generates sufficient revenues to keep the figures out of the red.
Presently, it appears that the Stockholmradio maritime services have a reasonably assured future for the next few years, as the Maritime Administration has agreed to a continued involvement in the maritime safety field. It is reasonable to expect that the flourishing mobile telephone market will further reduce traffic revenues from merchant shipping and boaters, maybe down to a level where the commercial aspects are neglected.
Finally the future of the Air/Ground HF voice services is very much linked to the rate of exchanging old aircraft for new.
Historically and by experience it has been found that the acquisition of new aircraft by an airline leads to the sale of the old to a more penny-pinching airline which usually don't want to make the investment in SATCOM and feels that HF has a satisfactory price/performance ratio for company communications. New aircraft on the other hand, are usually equipped with HF datalink, ACARS and SATCOM from the beginning.
Stockholmradio celebrated its 75th anniversary in 1989, and the possibilities that the station will be around in some form to celebrate its 100th anniversary have increased.
It can be appropriate in this context to quote an anecdote from the wireline telegraph days in the mid-19'th century, when a hurried customer rushed to the Stockholm Central telegraph office to hand in a telegram, asking the clerk at the counter when the office closes. The clerk responded:
"Close? We close earliest at doomsday, but quite late in the evening."
5. About the author
Mr. Karl-Arne Markström is a Senior Consultant with Telemar Scandinavia AB, Nacka Strand, Sweden, responsible for radio system engineering. He is associated with the Swedish branch of the URSI, the ITU/R Study Group 8, the Radio Technical Commission for Maritime Services and holds the amateur radio callsign SM0AOM since 1971.