Radiofax, also known as weatherfax (portmanteau word from the words "weather facsimile") and HF fax (due to its common use in the short waves), is an analogue

Analog signal

An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...

 mode for transmitting monochrome

Monochrome

Monochrome describes paintings, drawings, design, or photographs in one color or shades of one color. A monochromatic object or image has colors in shades of limited colors or hues. Images using only shades of grey are called grayscale or black-and-white...

 images. It was the predecessor to slow-scan television

Slow-scan television

Slow-scan television is a picture transmission method used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or color.A technical term for SSTV is narrowband television...

 (SSTV). Prior to the advent of the commercial telephone line "fax" machine, it was known, more traditionally, by the term "radiofacsimile". The cover of the regular NOAA publication on frequencies and schedules states "Worldwide Marine Radiofacsimile Broadcast Schedules".

Facsmile machines were used in the 1950s to transmit weather charts across the United States via land-lines first and then internationally via HF radio. Radio transmission of weather charts provides an enormous amount of flexibility to marine

Marine (ocean)

Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

 and aviation

Aviation

Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...

 users for they now have the latest weather information and forecasts at their fingertips to use in the planning of voyages.

Radiofax relies on facsimile

Facsimile

A facsimile is a copy or reproduction of an old book, manuscript, map, art print, or other item of historical value that is as true to the original source as possible. It differs from other forms of reproduction by attempting to replicate the source as accurately as possible in terms of scale,...

 technology where printed information is scanned line by line and encoded into an electrical signal which can then be transmitted via physical line or radio waves to remote locations. Since the amount of information transmitted per unit time is directly proportional to the bandwidth available, then the speed at which a weather chart can be transmitted will vary depending on the quality of the media used for transmission.

Today radiofax data is available via FTP

File Transfer Protocol

File Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...

 downloads from sites in the Internet

Internet

The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

 such as the ones hosted by the National Oceanic and Atmospheric Administration

National Oceanic and Atmospheric Administration

The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...

 (NOAA). Radiofax transmissions are also broadcast by NOAA from multiple sites in the country at regular daily schedules. Radio weatherfax transmissions are particularly useful to shipping, where there are limited facilities for accessing the Internet.

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).

Transmission details

Radiofax is transmitted in single sideband which is a refinement of amplitude modulation

Amplitude modulation

Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...

. The signal shifts up or down a given amount to designate white or black pixels. A deviation

Deviation

Deviation may refer to:* Deviation , the difference between the value of an observation and the mean of the population in mathematics and statistics** Standard deviation, which is based on the square of the difference...

 less than that for a white or black pixel is taken to be a shade of grey. With correct tuning (1.9 kHz below the carrier frequency for USB, above for LSB), the signal shares some characteristics with SSTV, with black at 1500 Hz and peak white at 2300 Hz.

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). 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

Pi

' is a mathematical constant that is the ratio of any circle's circumference to its diameter. is approximately equal to 3.14. Many formulae in mathematics, science, and engineering involve , which makes it one of the most important mathematical constants...

. 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	300 Hz	675 Hz	200 Hz 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	450 Hz	450 Hz
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

National Weather Service

The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...

 (NWS) of the National Oceanic and Atmospheric Administration

National Oceanic and Atmospheric Administration

The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...

 (NOAA).

Tropical and hurricane products come from the Tropical Analysis and Forecast Branch, part of the Tropical Prediction Center/National Hurricane Center

National Hurricane Center

The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...

. They are broadcast over US Coast Guard communication stations NMG

NMG (radio station)

NMG is the callsign of the National Hurricane Center's Atlantic basin radiofax radio station. It broadcasts from the United States Coast Guard station in New Orleans, Louisiana with 5 kilowatts of power....

, in New Orleans, LA, and NMC

NMC

NMC may refer to:* NMC Records, an Israeli record label and music company.* NMC Recordings, a record label and music company in the United Kingdom* National Meteorological Center, now the National Centers for Environmental Prediction...

, the Pacific master station on Point Reyes, CA. After Hurricane Katrina

Hurricane Katrina

Hurricane Katrina of the 2005 Atlantic hurricane season was a powerful Atlantic hurricane. It is the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall...

 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 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

Kodiak, Alaska

Kodiak is one of 7 communities and the main city on Kodiak Island, Kodiak Island Borough, in the U.S. state of Alaska. All commercial transportation between the entire island and the outside world goes through this city either via ferryboat or airline...

, and Department of Defense station KVM70 in Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

.

Ever since the RMS Titanic dramatized the dangers of icebergs in the North Atlantic, an International Ice Patrol

International Ice Patrol

The International Ice Patrol is an organization with the purpose of monitoring the presence of icebergs in the Atlantic and Arctic Oceans and reporting their movements for safety purposes. It is operated by United States Coast Guard but is funded by the 13 nations interested in trans-Atlantic...

 has also originated weather data, and its charts are broadcast by the Boston 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

Radioteletype

Radioteletype is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations, later superseded by personal computers running software to emulate teleprinters, connected by radio rather than a wired link.The term radioteletype is used to...

 (RTTY) for the rest of the period.

CBV, Playa Ancha Radio in Valparaiso

Valparaíso

Valparaíso is a city and commune of Chile, center of its third largest conurbation and one of the country's most important seaports and an increasing cultural center in the Southwest Pacific hemisphere. The city is the capital of the Valparaíso Province and the Valparaíso Region...

, Chile

Chile

Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

 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

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 has two stations, as does the Bureau of Meteorology in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. Most European countries have stations, as does Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

.

Kyodo News

Kyodo News

is a nonprofit cooperative news agency based in Minato, Tokyo. It was established in November 1945 and it distributes news to almost all newspapers, and radio and television networks in Japan. The newspapers using its news have about 50 million subscribers. K. K. Kyodo News is Kyodo News' business...

 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

Singapore

Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...

. 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.

History

• 1911: The first amplitude modulator for fax machines is patented, permitting transmission via telephone lines.
• 1913: Edouard Belin's Belinograph
• 1922: The first transatlantic facsimile services was provided by RCA.
• 1922–1925: RCA faxes photos across the Atlantic in six minutes; AT&T, RCA and Western Union develop "high-speed" fax systems. Dr Arthur Korn's facsimile system is used to transmit, by radio, a photograph of Pope Pius XI
  Pope Pius XI
  Pope Pius XI , born Ambrogio Damiano Achille Ratti, was Pope from 6 February 1922, and sovereign of Vatican City from its creation as an independent state on 11 February 1929 until his death on 10 February 1939...
  
   from Rome to Maine, USA. The picture is published the same day in the New York World newspaper—a major feat in an era when news pictures crossed the ocean by ship.
• 1925: AT&T wirephoto starts operations
• 1926: RCA radiophoto starts operations
• 1926: Rudolf Hell
  Rudolf Hell
  Rudolf Hell was a German inventor. He was born in Eggmühl, Germany.From 1919 to 1923 he studied electrical engineering in Munich....
  
   introduced the Hellschreiber
  Hellschreiber
  The Hellschreiber or Feldhellschreiber is a facsimile-based teleprinter invented by Rudolf Hell. Compared to contemporary teleprinters that were based on typewriter systems, the Hellschreiber was much simpler and more robust, with only two moving parts...
  
  .
• 1927: first Siemens-Karolus-Telefunken facsimile between Berlin and other European cities
• 1937: first broadcast of a radiofax newspaper, in the Minneapolis/St-Paul area
• 1939: W9XZY St. Louis delivers First Daily Newspaper by Radio Facsimile. More than 1,000 U.S. households are experimentally equipped with fax receivers that electronically print morning newspapers overnight.
• 1941: Fax is enlisted by the military to transmit maps, orders and weather charts during World War II.
• 1947: Alexander Muirhead's fax
• 1960: First SSTV test transmissions in the USA
• 1972: First SSTV transmissions in Germany

External links

• http://www.hffax.de/html/hauptteil_faxhistory.htm
• Marine Weatherfax NOAA broadcasts
• Schedules and frequencies
• Marine Weatherfax Chart Viewer for iPad