Maritime Fax Transmissions

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Radiofax, also known as weatherfax and HF fax (due to its common use in the short waves), is an analogue mode for transmitting images in grayscale. It is also related to slow-scan television (SSTV). The term weatherfax was coined after the technology that allows the transmission and reception of weather charts (surface analysis, forecasts, and others) from a transmission site (usually the meteorological office) to a remote site (where the actual users are).

Facsmile machines were used in the 1950's to transmit weather charts across the United States via land-lines first and then internationally via HF radio. Radio transmission of weather charts provides great flexibility to marine and aviation users, for they now have the latest weather information and forecasts at their disposal to use in the planning of voyages.

Radiofax relies on facsimile technology, where printed information is scanned line by line and encoded into an electrical signal which can then be transmitted over land-line or via radio waves to great distances. Since the amount of information transmitted per unit time is directly proportional to the bandwidth available, the speed at which a weather chart can be transmitted varies depending on the quality of the media used for transmission.

Today radiofax charts and images are available via FTP or HTTP downloads from sites in the Internet, such as the ones hosted by the National Oceanic and Atmospheric Administration (NOAA). Radiofax transmissions are also broadcast by NOAA from multiple sites in the USA at regular daily schedules. Radio weatherfax transmissions are particularly useful to shipping, where there are limited facilities for accessing the Internet. The German Meteorological Service (DWD) is another major producer of FAX charts, which are also transmitted on HF frequecies from a location near Kiel.

Contents

Transmission details

Radiofax is transmitted in single sideband and uses frequency modulation. The signal shifts up or down a given amount to designate white or black pixels. A deviation less than that for a white or black pixel is taken to be a shade of grey. With correct tuning (1.9kHz below the carrier frequency for USB, above for LSB), the signal shares some characteristics with SSTV, with black at 1500Hz and peak white at 2300Hz. The official ITU radio emission designation is F1C.

Usually, 120 lines per minute (LPM) are sent (For monochrome fax, possible values are: 60, 90, 100, 120, 180, 240. For colour fax, LPM can be: 120, 240).[1] A value known as the index of cooperation (IOC) must also be known to decode a radio fax transmission - this governs the image resolution, and derives from early radio fax machines which used drum readers, and is the product of the total line length and the number of lines per unit length (known sometimes as the factor of cooperation), divided by π (3.1416). Usually the IOC is 576.

Automatic Picture Transmission format (APT)

APT format permits unattended monitoring of services. It is employed by most terrestrial weather facsimile stations as well as geostationary weather satellites.

  • The start tone triggers the receiving system. It was originally meant to allow enough time for the drum of mechanical systems to get up to speed. It consists of rapid modulation of the video carrier, resulting in a characteristic rasp-like sound.
  • The phasing signal, consisting of a periodic pulse, synchronises the receiver so that the image will be centered on the paper.
  • The stop tone, optionally followed by black, marks the end of the transmission.


Signal Duration IOC576 IOC288 Remarks
Start tone 5s 300Hz 675Hz 200Hz for colour fax modes.
Phasing signal 30s White line interrupted by a black pulse.
Image Variable 1200 lines 600 lines At 120 lpm.
Stop tone 5s 450Hz 450Hz
Black 10s

Stations

Today, radiofax is primarily used worldwide for the dissemination of weather charts, satellite weather images, and forecasts to ships at sea. The oceans are covered by coastal stations in various countries.

In the United States, fax weather products are prepared by a number of offices, branches, and agencies within the National Weather Service (NWS) of the National Oceanic and Atmospheric Administration (NOAA).

  • Tropical and hurricane products come from the Tropical Analysis and Forecast Branch, part of the Tropical Prediction Center/National Hurricane Center. They are broadcast over US Coast Guard communication stations NMG, in New Orleans, LA, and NMC, the Pacific master station on Point Reyes, CA. After Hurricane Katrina damaged NMG, the Boston Coast Guard station NMF added a limited schedule of tropical warning charts. NMG is back at full capability, but NMF continues to broadcast these.
  • All other products come from the Ocean Prediction Center (OPC) of the National Weather Service (NWS), in cooperation with several other offices depending on the region and nature of information. These also use NMG, NMC, and NMF, plus Coast Guard station NOJ in Kodiak, Alaska, and Department of Defense station KVM70 in Hawaii.
  • Ever since the RMS Titanic dramatized the dangers of icebergs in the North Atlantic, an International Ice Patrol has also originated weather data. Its charts are broadcast by the Boston Coast Guard station during the prime iceberg season of February through September, using the callsign NIK.

A major producer of Canadian radiofax is the Canadian Forces METOC (Meteorology and Oceanography Centre) in Halifax, NS, using the communication station CFH. Charts are sent on the hour, then the station switches to radioteletype (RTTY) for the rest of the period.

In Europe the most commonly received weather FAX service is the German Meteorological Service (Deutscher Wetterdienst or DWD), which transmits from Offenbach throught the day. The DWD frequencies and callsigns are:[4]


Callsign Frequency Power
DDH3 3855.0 kHz 10 kW
DDK3 7880.0 kHz 20 kW
DDK6 13882.5 kHz 20 kW


CBV, Playa Ancha Radio in Valparaiso, Chile broadcasts a daily schedule of Armada de Chile weather fax for the southeastern Pacific, all the way to the Antarctic. Also in the Pacific, Japan has two stations, as does the Bureau of Meteorology in Australia. Most European countries have stations, as does Russia.

Kyodo News is the only remaining news agency to transmit news via radiofax. It broadcasts complete newspapers in Japanese and English, often at 60 lines per minute instead of the more normal 120 because of the greater complexity of written Japanese. A full day's news takes hours to transmit. Kyodo has a dedicated transmission to Pacific fishing fleets from Kagoshima Prefectural Fishery Radio, and a relay from 9VF, possibly still in Singapore. The frequencies formerly used by JJC radio outside Tokyo are now sent from an unknown location, using the same identification in Japanese as 9VF. They are still active and heard daily in 2010.

The Joint Operational Meteorology & Oceanography Centre, Nortwood, UK (callsign GYA) transmits various weather charts for the the Royal Navy on 2618.5, 4610.0, 6834.0, 8040.0, 11086.5, 12390.0 and 18261.0 kHz. The charts cover North Atlantic, Europe and the Persian Gulf areas.

Callsign Frequency Power Program
GYA 2618.5 kHz 10 kW Europe (2000-0600 UTC)
GYA 4610.0 kHz 10 kW Europe (24h)
GYA 6834.0 kHz 10 kW Persian Gulf (1800-0800 UTC)
GYA 8040.0 kHz 10 kW Europe (24h)
GYA 11886.5 kHz 10 kW Europe (0600-2000 UTC)
GYA 12390.0 kHz 10 kW Persian Gulf (24h)
GYA 18261.0 kHz 10 kW Persian Gulf (0800-1800 UTC)

List of FAX transmissions

(UTC) Station Callsign Frequencies Location Comments
0000 Wiluna VMW 7535, 10555, 15615 kHz AUSTRALIA Weather FAX*; 120/576
0000 USCG New Orleans, LA NMG (NMG-2) 4317.9, 8503.9, 12789.9 kHz UNITED STATES - Atlantic and Gulf Weather FAX*; 120/576
0000 Charleville VMC 5100, 11030, 13920 kHz AUSTRALIA Weather FAX*; 120/576
0000 Tokyo JMH 3622.5, 7795, 13988.5 kHz JAPAN Ice FAX; 120/576
0000 Tokyo JMH 3622.5, 7795, 13988.5 kHz JAPAN Ice FAX; 120/576
0000 Tokyo JMH 3622.5, 7795, 13988.5 kHz JAPAN Ice FAX; 120/576
0000 Casey, AUS VLM 7470 kHz ANTARCTICA Weather FAX*; 120/576
0000 Dakar 6VA/6VU 13667.5, 19750 kHz SENEGAL Weather FAX; 120/576
0000 Tokyo JMH 3622.5, 7795, 13988.5 kHz JAPAN Weather FAX*; 120/576
0000 USCG Boston, MA NMF/NIK/NMF-7 6340.5, 9110 kHz UNITED STATES - Atlantic and Gulf Weather FAX*; 120/576
0000 Honolulu, HI KVM70 11090 kHz UNITED STATES - Hawaii Weather FAX*; 120/576
0000 Halifax, N.S. VCS/CFH 122.5 MHz, 4271, 6496.4, 10536, 13510 kHz CANADA - Arctic and Atlantic Weather FAX*; 120/576
0000 USCG Point Reyes, CA NMC/NMC-17 8682, 12786, 17151.2 kHz UNITED STATES - Pacific Weather FAX*; 120/576
0001 Halifax, N.S. VCS/CFH 122.5 MHz, 4271, 6496.4, 10536, 13510 kHz CANADA - Arctic and Atlantic Ice FAX*; 120/576
0010 Iqaluit, N.T. VFF 3251.1, 7708.1 kHz CANADA - Arctic and Atlantic Ice FAX; 120/576 (Resolute)
0130 Tokyo JMH 3622.5, 7795, 13988.5 kHz JAPAN Ice FAX; 120/576
0140 USCG Point Reyes, CA NMC/NMC-17 4346 kHz UNITED STATES - Pacific Weather FAX*; 120/576
0200 Inuvik, N.W.T. VFA 8457.8 kHz CANADA - Arctic and Atlantic Weather and ice FAX; 120/576
0230 USCG Boston, MA NMF/NIK/NMF-7 4235 kHz UNITED STATES - Atlantic and Gulf Weather FAX*; 120/576
0400 Kodiak, AK NOJ 2054, 4298, 8459, 12412.5 kHz Weather and ice FAX*; 120/576
0430 Cape Naval (NAVCOMCEN Cape) ZSJ 7508, 13538 kHz SOUTH AFRICA Weather FAX*; 120/576
0430 Cape Naval (NAVCOMCEN Cape) ZSJ 4014 kHz SOUTH AFRICA Weather FAX*; 120/576
0430 Offenbach/Pinneberg DDH/DDK 3855, 7880, 13882.5 kHz GERMANY - North Sea Weather FAX*; 120/576
0438 USCG Boston, MA NMF/NIK/NMF-7 4235, 6340.5, 9110 kHz UNITED STATES - Atlantic and Gulf Ice FAX; 120/576 (Feb. - Aug.)
0500 Cape Naval (NAVCOMCEN Cape) ZSJ 4014 kHz SOUTH AFRICA Weather FAX*; 120/576
0500 Cape Naval (NAVCOMCEN Cape) ZSJ 7508, 13538 kHz SOUTH AFRICA Weather FAX*; 120/576
0500 Iqaluit, N.T. VFF 3251.1, 7708.1 kHz CANADA - Arctic and Atlantic Ice FAX; 120/576
0519 Honolulu, HI KVM70 9982.5 kHz UNITED STATES - Hawaii Weather FAX*; 120/576
0530 Pevek 148 kHz RUSSIA - Northern Coasts Ice FAX, 90/576
0600 RN Northwood GYA 2618.5 kHz UNITED KINGDOM
0630 Cape Naval (NAVCOMCEN Cape) ZSJ 18238 kHz SOUTH AFRICA Weather FAX*; 120/576
0630 Cape Naval (NAVCOMCEN Cape) ZSJ 7508, 13538 kHz SOUTH AFRICA Weather FAX*; 120/576
0655 USCG Point Reyes, CA NMC/NMC-17 4346 kHz UNITED STATES - Pacific Weather FAX*; 120/576
0700 Iqaluit, N.T. VFF 3251.1, 7708.1 kHz CANADA - Arctic and Atlantic Ice FAX; 120/576 (Resolute)
0700 Murmansk UDK/UDK2 6446, 7907, 8444 kHz RUSSIA - Northern Coasts Weather and ice FAX*; 120/576
0730 Cape Naval (NAVCOMCEN Cape) ZSJ 18238 kHz SOUTH AFRICA Weather FAX*; 120/576
0730 Cape Naval (NAVCOMCEN Cape) ZSJ 7508, 13538 kHz SOUTH AFRICA Weather FAX*; 120/576
0745 Rio de Janeiro Naval PWZ-33 12665, 16978 kHz BRAZIL Weather FAX; 120/576
0800 Cape Naval (NAVCOMCEN Cape) ZSJ 7508, 13538, 18238 kHz SOUTH AFRICA Ice FAX; 120/576
0800 Murmansk UDK/UDK2 6446, 7907, 8444 kHz RUSSIA - Northern Coasts Weather and ice FAX*; 120/576
0800 RN Northwood GYA 6834 kHz UNITED KINGDOM
0900 Athens SWA 8106.9 kHz GREECE Weather FAX; 120/576
0900 Charleville VMC 2628 kHz AUSTRALIA Weather FAX*; 120/576
0930 Offenbach/Pinneberg DDH/DDK 3855, 7880, 13882.5 kHz GERMANY - North Sea Ice FAX*; 120/576
0950 Kodiak, AK NOJ 2054, 4298, 8459, 12412.5 kHz Weather and ice FAX*; 120/576
1000 Iqaluit, N.T. VFF 3251.1, 7708.1 kHz CANADA - Arctic and Atlantic Weather FAX; 120/576
1007 Offenbach/Pinneberg DDH/DDK 3855, 7880, 13882.5 kHz GERMANY - North Sea Ice FAX*; 120/576
1019 Tokyo JMH 3622.5, 7795, 13988.5 kHz JAPAN Ice FAX; 120/576
1030 Cape Naval (NAVCOMCEN Cape) ZSJ 18238 kHz SOUTH AFRICA Weather FAX*; 120/576
1030 Cape Naval (NAVCOMCEN Cape) ZSJ 7508, 13538 kHz SOUTH AFRICA Weather FAX*; 120/576
1100 Iqaluit, N.T. VFF 3251.1, 7708.1 kHz CANADA - Arctic and Atlantic Weather FAX; 120/576 (Resolute)
1100 Wiluna VMW 5755 kHz AUSTRALIA Weather FAX*; 120/576
1100 Cape Naval (NAVCOMCEN Cape) ZSJ 18238 kHz SOUTH AFRICA Weather FAX*; 120/576
1100 Cape Naval (NAVCOMCEN Cape) ZSJ 7508, 13538 kHz SOUTH AFRICA Weather FAX*; 120/576
1115 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Weather FAX; 120/576
1120 USCG Point Reyes, CA NMC/NMC-17 4346 kHz UNITED STATES - Pacific Weather FAX*; 120/576
1121 Sydney, N.S. VCO 6915.1 kHz CANADA - Arctic and Atlantic Ice FAX; 120/576
1130 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Weather FAX; 120/576
1130 Pevek 148 kHz RUSSIA - Northern Coasts Ice FAX, 90/576
1142 Sydney, N.S. VCO 6915.1 kHz CANADA - Arctic and Atlantic Ice FAX; 120/576
1200 USCG New Orleans, LA NMG/NMG-2 17146.4 kHz UNITED STATES - Atlantic and Gulf Weather FAX*; 120/576
1400 Murmansk UDK/UDK2 6446, 7907, 8444 kHz RUSSIA - Northern Coasts Weather and ice FAX*; 120/576
1400 USCG Point Reyes, CA NMC/NMC-17 4346 kHz UNITED STATES - Pacific Weather FAX*; 120/576
1400 USCG Boston, MA NMF/NIK/NMF-7 12750 kHz UNITED STATES - Atlantic and Gulf Weather FAX*; 120/576
1430 Murmansk UDK/UDK2 6446, 7907, 8444 kHz RUSSIA - Northern Coasts Weather and ice FAX*; 120/576
1430 Pevek 148 kHz RUSSIA - Northern Coasts Ice FAX, 90/576
1520 Offenbach/Pinneberg DDH/DDK 3855, 7880, 13882.5 kHz GERMANY - North Sea Ice FAX*; 120/576
1530 Cape Naval (NAVCOMCEN Cape) ZSJ 18238 kHz SOUTH AFRICA Weather FAX*; 120/576
1530 Cape Naval (NAVCOMCEN Cape) ZSJ 7508, 13538 kHz SOUTH AFRICA Weather FAX*; 120/576
1540 Offenbach/Pinneberg DDH/DDK 3855, 7880, 13882.5 kHz GERMANY - North Sea Ice FAX*; 120/576
1600 USCG Boston, MA NMF/NIK/NMF-7 6340.5, 9110, 12750 kHz UNITED STATES - Atlantic and Gulf Ice FAX; 120/576 (Feb. - Aug.)
1600 Kodiak, AK NOJ 2054, 4298, 8459, 12412.5 kHz Weather and ice FAX*; 120/576
1630 Rio de Janeiro Naval PWZ-33 12665, 16978 kHz BRAZIL Weather FAX; 120/576
1630 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Weather FAX; 120/576
1630 Inuvik, N.W.T. VFA 8457.8 kHz CANADA - Arctic and Atlantic Weather and ice FAX; 120/576
1645 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Weather FAX; 120/576
1719 Honolulu, HI KVM70 16135 kHz UNITED STATES - Hawaii Weather FAX*; 120/576
1741 Sydney, N.S. VCO 6915.1 kHz CANADA - Arctic and Atlantic Ice FAX; 120/576
1810 USCG Boston, MA NMF/NIK/NMF-7 6340.5, 9110, 12750 kHz UNITED STATES - Atlantic and Gulf Ice FAX; 120/576 (Feb. - Aug.)
1840 USCG Point Reyes, CA NMC/NMC-17 22527 kHz UNITED STATES - Pacific Weather FAX*; 120/576
1900 Charleville VMC 20469 kHz AUSTRALIA Weather FAX*; 120/576
1900 Northwood, UK GYA 11086.5 EUROPE Weather FAX; 120/576
1915 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Weather FAX; 120/576
1930 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Weather FAX; 120/576
2000 Murmansk UDK/UDK2 6446, 7907, 8444 kHz RUSSIA - Northern Coasts Weather and ice FAX*; 120/576
2100 Offenbach/Pinneberg DDH/DDK 3855, 7880, 13882.5 kHz GERMANY - North Sea Ice FAX*; 120/576
2100 Wiluna VMW 18060 kHz AUSTRALIA Weather FAX*; 120/576
2100 Iqaluit, N.T. VFF 3251.1, 7708.1 kHz CANADA - Arctic and Atlantic Weather FAX; 120/576
2115 Offenbach/Pinneberg DDH/DDK 3855, 7880, 13882.5 kHz GERMANY - North Sea Ice FAX*; 120/576
2125 Iqaluit, N.T. VFF 3251.1, 7708.1 kHz CANADA - Arctic and Atlantic Ice FAX; 120/576
2150 Kodiak, AK NOJ 2054, 4298, 8459, 12412.5 kHz Weather and ice FAX*; 120/576
2200 Sydney, N.S. VCO 4416 kHz CANADA - Arctic and Atlantic Ice FAX; 120/576
2200 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Weather FAX; 120/576
2215 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Ice FAX; 120/576
2222 Halifax, N.S. VCS/CFH 122.5 MHz, 4271, 6496.4, 10536, 13510 kHz CANADA - Arctic and Atlantic Ice FAX*; 120/576
2230 Cape Naval (NAVCOMCEN Cape) ZSJ 4014 kHz SOUTH AFRICA Weather FAX*; 120/576
2230 Cape Naval (NAVCOMCEN Cape) ZSJ 7508, 13538 kHz SOUTH AFRICA Weather FAX*; 120/576
2230 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Weather FAX; 120/576
2301 Halifax, N.S. VCS/CFH 122.5 MHz, 4271, 6496.4, 10536, 13510 kHz CANADA - Arctic and Atlantic Ice FAX*; 120/576
2310 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Weather FAX; 120/576
2320 USCG Point Reyes, CA NMC/NMC-17 22527 kHz UNITED STATES - Pacific Weather FAX*; 120/576
2325 Valparaiso Playa Ancha CBV 4228, 8677, 17146.4 kHz CHILE Weather FAX; 120/576
2330 Iqaluit, N.T. VFF 3251.1, 7708.1 kHz CANADA - Arctic and Atlantic Weather FAX; 120/576 (Resolute)
2331 Sydney, N.S. VCO 4416 kHz CANADA - Arctic and Atlantic Ice FAX; 120/576

Gallery of FAX receptions


References

  1. Multimode image and data decoding software for soundcards
  2. 'Radio printing' sent newspapers through the waves
  3. First daily newspaper by Radio Facsimile
  4. Deutscher Wetterdienst FAX broadcasts for shipping

External links

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