Fact-checked by Grok 2 weeks ago

Radiofax

Radiofax, also known as radio facsimile or fax, is an analog technology that transmits still —such as weather charts, documents, and photographs—over radio waves using frequency-modulated audio signals generated by scanning the original line by line. The process encodes variations between black (typically 1500 Hz tone) and white (2300 Hz tone), with transmissions occurring at speeds like 120 lines per minute and an index of cooperation of 576 for , allowing reception on shortwave radios connected to recorders or software-equipped computers. Originally developed for transfer, radiofax has been a vital tool for remote communication where digital alternatives are unavailable or unreliable. The roots of radiofax trace back to early 19th-century facsimile experiments, with Scottish inventor Alexander Bain patenting the first electrochemical recording telegraph in 1843, which laid the groundwork for scanning and transmitting images electrically. Radio-specific advancements emerged in the early 20th century; German engineer Arthur Korn demonstrated photo transmission in 1904, and by 1924, engineers Richard H. Ranger and Charles J. Young achieved the first transatlantic radiofax of an image—President Calvin Coolidge's portrait—from to . In the 1930s, inventor William G. H. Finch refined the technology with recording, enabling experimental broadcasts like the daily facsimile newspaper from station W9XZY starting in 1939, while 's systems supported newspaper photo distribution and weather map delivery to ships. During , militaries on both sides employed radiofax for reconnaissance photos, artillery targeting, and weather dissemination, highlighting its strategic value in analog form before . Postwar, radiofax evolved into a standard for and ; the U.S. Weather Bureau began broadcasting weather charts via radiofacsimile in 1926, with postwar expansion through high-frequency radio from U.S. stations for international use. These broadcasts, which take about 10 minutes per chart, provide essential data on , , and fronts for vessels at sea. As of 2025, radiofax remains in active use despite digital alternatives like files, with NOAA continuing transmissions from four U.S. sites—; , ; Belle Chasse, ; and —to support global shipping and ensure safety in areas with limited satellite connectivity. International stations, including Germany's DWD and Australia's VMC, also contribute to this network, preserving radiofax as a reliable, low-bandwidth legacy system.

Overview and History

Definition and Basic Principles

Radiofax, also known as radiofacsimile, HF fax, or weatherfax, is an analog mode for transmitting or images via high-frequency () radio waves in the 3-30 MHz range. This technology converts fixed graphic materials, such as charts, into electrical signals for remote reproduction on receiving equipment. The basic principles of radiofax center on line-by-line scanning of the source image using a rotating or electronic to capture optical variations. These variations are then encoded into audio tones via (FSK), a form of (F3C emission), where white pixels generate higher frequencies (e.g., 2300 Hz) and black pixels lower frequencies (e.g., 1500 Hz), centered around 1900 Hz with a ±400 Hz shift. The resulting signal is transmitted using single sideband (SSB) modulation over channels, allowing reception on compatible radio equipment connected to a or . Key parameters include a typical of 1-2 mm per line vertically, determined by scanning density, and an of 1:6 (height to width) to ensure proportional . The Index of Cooperation (IOC) measures quality, calculated as \pi \times drum circumference in mm divided by line spacing in mm; for example, an IOC of 576 provides standard quality with a line spacing of approximately 0.83 mm on a drum with 152 mm circumference. Primarily, radiofax serves the purpose of image dissemination in remote or mobile settings lacking reliable wired or connectivity, such as vessels and operations.

Historical Development

The development of radiofax, or radio , began in the early with foundational patents enabling image transmission over communication lines. In 1911, the first amplitude modulator for machines was patented, allowing for the transmission of images via lines and laying the groundwork for radio-based adaptations. Korn demonstrated the first transmission of photographs in 1904, adapting earlier wired systems for radio use. This innovation facilitated the shift toward methods, culminating in 1924 when Richard H. Ranger, an at the Radio Corporation of America (), invented the photoradiogram. On November 29, 1924, Ranger successfully transmitted the first photograph—a of President —from to via , marking the debut of transoceanic radio technology. Advancements in focused on practical applications for , particularly newspapers. In 1931, Ernst F. W. Alexanderson, chief engineer at , developed a system for the radio transmission of pictures, enabling the scanning and sending of images line by line. Building on this, the Finch Facsimile system, invented by W.G.H. Finch, emerged in the late 1930s as a low-cost method for transmitting "radio newspapers" to homes via AM radio stations and wire recorders. From 1938 to 1940, experiments like those by demonstrated domestic subscription services, printing news on continuous paper rolls, though widespread adoption was limited by the onset of . During , radiofax saw expanded military use for transmitting reconnaissance photos, maps, and weather charts, supporting operational needs in remote and mobile environments. By the late 1940s, technological refinements allowed for miniaturized receivers, such as those integrated into Western Union's "Telecar" telegram delivery vehicles, enhancing portability for field applications. In the post-war era, radiofax became integral to and . The U.S. (NWS) adopted radiofax in the 1950s to broadcast weather maps, providing mariners with graphical forecasts that served as a lifeline for global navigation until digital alternatives emerged. A notable milestone occurred in 1966 when the Soviet probe achieved the first soft landing on the and transmitted photofacsimile images of the lunar surface back to Earth, using standard news wire facsimile machines for decoding at receiving stations. By the 1970s, (SSTV), a related analog technology for transmitting images including motion over shortwave, gained popularity among amateurs, offering improved resolution and color capabilities compared to traditional radiofax. In the from the 1970s to 2025, radiofax has transitioned amid advancements like , yet persists in maritime communications due to the reliability of high-frequency () radio in areas without . The NWS continues NOAA broadcasts, with 2020s receivers increasingly employing to decode analog transmissions, enabling software-based hybrid systems for enhanced clarity on personal computers and SDR hardware. Newspaper applications have largely declined, but weatherfax schedules remain active, including the Met Office's transmissions from Northwood (callsign GYA) as of 2025, providing essential charts to vessels worldwide.

Applications

Weatherfax

Weatherfax, a specialized application of radiofax technology, emerged in the 1950s when the U.S. —now part of the (NOAA)—initiated high-frequency (HF) broadcasts of weather maps to support marine and aviation users. These early transmissions provided critical graphical weather data to vessels and aircraft operating in areas with limited communication infrastructure, marking the beginning of radiofax as a reliable tool for meteorological dissemination at sea. The content transmitted via weatherfax includes a variety of meteorological charts essential for and safety, such as surface charts depicting current patterns, wind and forecasts for 24, 48, 72, and 96 hours, satellite composites like imagery, and upper-air charts including 500 and 850 levels. Broadcasts follow typical 24-hour cycles aligned with (UTC) updates at 00Z, 06Z, 12Z, and 18Z, with maps refreshed every 6 to 12 hours to reflect evolving conditions; for example, NOAA's station (NMF) transmits North Atlantic surface analyses and charts multiple times daily on frequencies like 4235 kHz and 9110 kHz. These schedules ensure continuous coverage for global maritime regions, with stations such as , (NMC), and New Orleans, (NMG), handling Pacific and transmissions, respectively. As of 2025, fax remains essential for ships navigating remote oceans where satellite or is unreliable or unavailable, with NOAA continuing broadcasts in the WEFAX format through dedicated stations to deliver meteorological data. While alternatives like (FTP) supplements are increasingly integrated for enhanced accessibility—allowing users to request charts via to [email protected]—the analog method persists as a vital layer, particularly for transoceanic voyages in the North Atlantic where NOAA's NMF broadcasts provide indispensable information. The advantages of weatherfax lie in its low-bandwidth requirements, resembling audio signals that can be received using simple single-sideband (SSB) radios without specialized equipment, making it cost-effective and accessible for smaller vessels. This simplicity enables reception on standard HF setups during extended voyages, such as those crossing the North Atlantic, where it supports strategic weather avoidance and enhances safety without dependency on high-data satellite links. Despite its enduring utility, weatherfax faces challenges including vulnerability to solar interference from flares and geomagnetic storms, which can cause signal blackouts and disrupt reception for hours or days by altering ionospheric . Usage has shown signs of decline amid the rise of digital satellite systems, though it is far from obsolete; reports from 2024 and 2025 highlight increased reliance on weatherfax during satellite outages and events, underscoring its role as a for critical .

Newspaper Fax

Radiofax found one of its earliest and most ambitious applications in the dissemination of content, allowing printed pages to be transmitted over radio waves and reproduced on receiving devices. In , broadcasters experimented with sending full editions or bulletins directly to homes, envisioning a "newspaper of the air" that could deliver timely without physical . These efforts primarily used shortwave or ultrahigh frequency (UHF) bands, with systems scanning pages line by line and modulating the signal for facsimile reproduction on thermal or . Early experiments began in the mid-1930s, with developing a photoelectric scanning system that enabled the transmission of newspaper images and text. The first regular radiofax newspaper broadcasts using technology started in February 1939 from station W9XZY in , , operating on 31,600 kHz with 100 watts, delivering daily editions overnight to subscribers within a 20-mile radius. Concurrently, inventor William G. H. introduced his amplitude-modulated facsimile system in 1933, with commercial tests by 1935 through Finch Telecommunications Laboratories; stations like WWJ in transmitted bulletins using this setup as early as 1938, printing 5-inch-wide pages on . By 1939, at least nine U.S. AM stations, including WOR in and WGN in , were authorized by the FCC for experimental overnight facsimile news services, often limited to 6 hours for multi-page editions due to regulatory noise restrictions. Usage peaked in the late 1930s with over two dozen U.S. newspapers adopting radiofax for domestic delivery, but it saw limited expansion during and after World War II for international news to remote areas, hampered by paper shortages and wartime priorities. Post-war, the technology persisted in niche international contexts, such as Japan's Kyodo News Agency using single-sideband high-frequency (SSB HF) transmissions from Tokyo's JJC station to broadcast Japanese and English newspapers to Pacific fishing fleets and isolated regions. These broadcasts, starting in the mid-20th century, focused on sequential page delivery for news, sports, and navigational updates, serving areas with limited print infrastructure. Technical adaptations for newspaper transmission involved high-resolution scanning of pages to capture fine text and images, followed by sequential broadcasting with phasing signals—periodic pulses for line synchronization—and optional stop tones to mark page ends. Finch's system operated at around 60 lines per minute (LPM), taking approximately 20 minutes per 12-inch page, while RCA setups achieved similar speeds, often requiring 10-20 minutes per page at 60-120 LPM depending on resolution and content density. Receivers, priced at $60-260, used thermal or carbon mechanisms to print grayscale reproductions, with synchronization ensured by 60 Hz tones to align the image on the paper roll. By the 1950s, radiofax newspapers declined sharply, replaced by faster wire services, , and eventually the , due to slow times, high equipment costs, static interference, and lack of standardization. As of 2025, widespread adoption never materialized, but continues niche HF broadcasts from JJC on 16,971 kHz, transmitting full editions at 60 LPM for Pacific audiences, including morning and evening news in and English. The concept of radiofax newspapers influenced early broadcast media by promoting the idea of instantaneous, wireless print delivery in , inspiring demonstrations at events like the and fostering visions of integrated radio-print ecosystems, though public adoption was minimal owing to technical limitations.

Other Uses

Radiofax found applications in military operations beyond standard weather dissemination, particularly for transmitting maps, orders, and imagery in challenging environments. During , the U.S. Army Air Corps adopted facsimile transmission in 1943 for relaying weather maps and other graphics, enhancing coordination in remote theaters where wired infrastructure was unavailable. In the era, military forces utilized radiofax for secure image relay in isolated operations, such as relaying reconnaissance-derived charts from forward bases to command centers, leveraging its robustness over high-frequency radio links in contested areas. In space exploration, radiofax principles enabled early interplanetary image transmission. The Soviet Luna 9 mission in 1966 achieved the first soft landing on the Moon and used a facsimile-style camera to scan and transmit panoramic images back to Earth via radio signals, with the lander sending 27 frames over three days that revealed the lunar surface's rocky horizon and craters. Early U.S. Mariner probes, such as Mariner 4 in 1965, employed similar facsimile camera systems to capture and relay close-up images of Mars, marking the first planetary photographs transmitted over vast distances using analog scanning techniques adapted for deep-space radio. Amateur radio enthusiasts have long incorporated radiofax into hobbyist activities, often receiving weatherfax broadcasts for signal decoding practice. Modern ham operators use shortwave receivers and software like to capture and decode WEFAX signals from stations such as NOAA's, fostering skills in data modes while monitoring global maritime forecasts. As a digital evolution of radiofax's analog image exchange, (SSTV) emerged in the among amateurs, allowing real-time static image transmission over voice-sideband frequencies, building on facsimile's line-scanning foundation for in amateur bands. Other niche applications included press photo services and support in the mid-20th century. In the 1940s and 1950s, radiophoto systems extended technology over radio links, enabling news agencies like the to transmit breaking images from remote correspondents to newspapers, such as event photos scanned and broadcast via shortwave for rapid domestic relay. Pre-satellite era relied on radiofax for disseminating en route charts and weather overlays, with pilots tuning receivers to military or civilian stations for updated graphical forecasts essential for transoceanic flights lacking real-time satellite data. By 2025, radiofax remains rare and largely historical, supplanted by digital satellite and internet-based imagery, though it retains niche relevance in emergencies. In disaster zones with disrupted infrastructure, such as the 2024 earthquake in , radiofax broadcasts from services like provided critical updates to affected areas, serving as a resilient analog backup for disseminating maps and alerts when power grids and cellular networks fail.

Technical Transmission

Signal Generation and Modulation

In historical radiofax systems, image preparation involved wrapping the original or around a rotating , where a source and phototube (or photocell) scanned it line by line to detect variations in , converting the analog into a series of elemental areas through rasterization. The of this rasterization was governed by the Index of Cooperation (IOC), a defining the total number of picture elements per revolution of the , resulting in horizontal resolutions of approximately 200 elemental areas per inch for standard setups (e.g., IOC 576 for standard weather maps). Modern electronic preparation, however, uses files (e.g., or at 1809 pixels wide) that are processed line by line to match these standards before . The core of signal generation lies in encoding the rasterized image using (FSK) to produce an audio-frequency tone signal, where black areas correspond to a Hz and white areas to a 2300 Hz (or inverted in some variants, with white at Hz and black at 2300 Hz), resulting in an Hz total shift. This varying tone signal, representing through proportional shifts between the extremes, is then fed into a single-sideband () modulator to impose it on a high-frequency () carrier, typically in the 8-16 MHz for global propagation. The resulting emission is classified as F1C under ITU designations, occupying a narrow of 400-500 Hz suitable for voice-grade radio channels. Synchronization is essential to align the transmitter and scanning rates and prevent image skew; transmissions commence with a start tone of 300 Hz for 5 seconds, followed by phasing lines—alternating bars of nearly full black (95%) interrupted by thin white pulses (5%) over 20-30 seconds—that allow the to calibrate its or line advance, and end with a stop tone of 450 Hz for 5 seconds. These phasing elements ensure precise and vertical alignment without ongoing per-line pulses. Transmission speeds are standardized to balance image quality and channel efficiency, with common rates of 60, 90, or 120 lines per minute (LPM); for instance, 120 LPM is widely used for weatherfax broadcasts, completing a typical chart in several minutes while maintaining compatibility with IOC 576. Equipment for signal generation has evolved significantly from the 1930s, when vacuum-tube scanners, phototubes, and analog modulators (e.g., MD-168A/UX converters) dominated naval and meteorological stations, to contemporary software-defined radios (SDRs) as of 2025, where tools like FLDigi enable fully digital image loading, FSK tone synthesis, and SSB modulation via computer interfaces for amateur and experimental transmissions.

Reception and Decoding

Reception of radiofax signals typically requires a standard high-frequency (HF) single sideband (SSB) receiver tuned to the broadcast frequency minus approximately 1.9 kHz in upper sideband (USB) mode to center the audio tones properly. The receiver's audio output is then connected via a patch cable to a dedicated fax demodulator, or more commonly in modern setups, to a personal computer's sound card input for software-based processing. Popular software tools as of 2025 include SeaTTY, fldigi, and MultiPSK, which handle the decoding from the audio signal. An appropriate antenna, such as a dipole or active HF antenna, is essential to achieve sufficient signal-to-noise ratio (SNR), with grounding and placement away from noise sources recommended to minimize interference. The demodulation process begins with (FSK) detection, where the receiver converts the modulated audio tones—typically 1500 Hz for black pixels and 2300 Hz for white pixels—into binary representations of the image data. A phasing signal, transmitted for several seconds before the image data (often 20-40 lines of alternating pulses), enables initial to align the lines and correct for any drift or clock mismatches. Line is maintained through detection of start pulses or ongoing tone patterns, with software adjustments for slant (rotation) and offset to compensate for tuning errors or propagation-induced shifts. This analog-derived process lacks robust digital error correction, relying instead on basic noise filtering to mitigate distortions. Historically, decoded signals were output to thermal paper printers in dedicated receivers, such as Alden models, which used electrosensitive or chemically treated rolls to produce direct prints of weather charts or images. In contemporary systems, the output is primarily , displaying or images on computer screens via software interfaces, with options to save as or files for later printing on standard inkjet printers if needed. Common challenges in include propagation fading due to ionospheric variations, which can cause signal strength fluctuations and result in incomplete or blurred images, particularly during nighttime or over long distances. Interference from other signals or further degrades quality, with low SNR leading to or loss of fine details in the decoded . Modern tools address these issues through software-defined radios (SDRs), such as the SDRplay RSPduo or KiwiSDR, which enable automated tuning, enhanced filtering, and direct digital for improved . Additionally, applications integrating GPS for precise timing help align receptions with broadcast schedules, reducing manual intervention.

Formats

WEFAX Standard

The WEFAX (Weather Facsimile) format evolved in the 1960s from U.S. Navy applications for transmitting , initially leveraging (APT) systems on naval ships and remote stations to support maritime operations in areas with limited communication infrastructure. It was standardized in the 1970s by the International Radio Consultative Committee (CCIR) for high-frequency () radio transmission, establishing a common analog protocol for global weather data dissemination. The transmission structure begins with a header featuring a start signal of 5 seconds of alternating black and white tones at 300 Hz, followed by a phasing signal consisting of 60 scan lines, each comprising three black-white cycles with a 5 ms white portion for . The main data follows in raster format, where each line starts with a 25 ms white level sync pulse and 475 ms of variable tone content representing the picture elements, scanned sequentially until the image is complete. The footer includes an end-of-transmission (EOT) signal of 5 seconds of alternating black and white at 450 Hz, followed by 10 seconds of black tone to signal completion. Key parameters include an Index of Cooperation (IOC) of 576, which defines the helical scan resolution on facsimile drums, and a transmission speed of 120 lines per minute (LPM), equivalent to 2 lines per second. The modulation uses (FSK) with a 1900 Hz , a 400 Hz shift ( at +400 Hz, black at -400 Hz), enabling typical image dimensions such as 286 lines high by 1810 pixels wide for an A4-equivalent chart. is supported through intermediate frequencies between and black tones, with varying durations within each line's 475 ms window to represent shades. WEFAX remains the dominant format for NOAA's HF weather broadcasts and international marine services, providing reliable dissemination of charts and satellite images to ships via scheduled transmissions. As of 2025, while satellite-based WEFAX has largely transitioned to digital protocols like Low Rate Information Transmission (LRIT), HF radiofax retains its core analog structure with minor enhancements in hybrid receiver software for improved decoding stability.

Automatic Picture Transmission (APT)

Automatic Picture Transmission (APT) was developed in the 1960s by the () as an analog system for real-time image transmission from meteorological satellites, initially tested on TIROS-8 in December 1963 and first operational on Nimbus 1 in August 1964. The format originated to enable low-cost ground stations worldwide to receive cloud cover photographs directly from polar-orbiting satellites without complex equipment, addressing limitations in early observation by allowing automated, unattended image capture. Adapted for radiofax in the 1970s, APT facilitated similar for terrestrial broadcasts of satellite-derived , permitting receivers to activate and record transmissions remotely without operator intervention. The APT transmission sequence is designed for reliable in unattended operations. It commences with a 5-second start tone at 300 Hz (for IOC 576 mode) to trigger activation, followed by a 30-second phasing signal of alternating black and lines—typically a black line interrupted by a pulse every 186 pixels—to align the 's scan timing and index of cooperation. The main image phase then transmits the grayscale data, often 1200 lines at 120 lines per minute (LPM) for a standard 10-minute chart, before ending with a 5-second stop tone at 450 Hz, optionally followed by 10 seconds of black to ensure complete recording. This structure mirrors the satellite heritage while accommodating propagation variability. Key parameters of APT include a line rate of 120 LPM for the original satellite configuration and HF radiofax, providing compatibility with standard facsimile equipment. The format uses an Index of Cooperation (IOC) of 576, providing 1810 pixels per line for moderate resolution, and supports images up to 1200 lines, though shorter 800-line variants were common for quicker transmissions. APT's primary advantages lie in its , allowing timer-independent recording via tone detection, which was essential for relaying early NOAA polar orbiter to remote and meteorological stations without dedicated attendance. This enabled widespread dissemination of real-time weather data, such as cloud patterns from TIROS and missions, enhancing global forecasting accessibility in resource-limited areas. As of 2025, direct APT transmissions have been phased out following the decommissioning of on August 19, 2025, with modern polar orbiters shifting to digital formats like HRPT for higher . However, the APT protocol persists in radiofax for broadcasting legacy weather charts and emulated images, supported by software decoders for historical and use.

Legacy and Variant Formats

The Finch Facsimile system, developed by inventor William G. H. Finch in the 1930s, represented an early commercial effort to transmit newspapers over radio waves for home reception. The system employed a scanning mechanism to convert printed pages into electrical signals broadcast via shortwave, with receivers using a on chemically treated paper to reproduce text and images line by line. Transmission times averaged 15 to 20 minutes per page, limiting its practicality for timely news delivery, though it was demonstrated at the . By the late , the technology became obsolete as television's rise provided faster visual news, leading to Finch's company bankruptcy in 1952. RCA's Wirephoto system, introduced in the , facilitated the rapid transmission of press photographs using telegraph, telephone, or radio lines, marking a shift toward higher-fidelity image distribution for newspapers. The process involved wrapping originals around a rotating drum scanned by a to generate analog signals, often at speeds around 60 lines per minute to prioritize vertical for sharper photo details. Integrated with existing wire services like the , it enabled transatlantic sends in hours rather than days, but required specialized equipment and was gradually supplanted by digital alternatives. Earlier precursors included Richard H. Ranger's photoradiogram system from the 1920s, which achieved the first transoceanic radio transmission of a in 1924—a portrait of President from to —using techniques that laid groundwork for later standards. Soviet adaptations extended radiofax into , notably with the Luna 9 mission in 1966, where images of the lunar surface were broadcast in the standard Radiofax format at 10 lines per minute and 560 lines resolution, allowing global decoding including by British amateurs before official release. In , (SSTV) emerged as a bridge from analog radiofax to modes, enabling hobbyists to transmit or color pictures over voice frequencies since the 1950s, with modern software handling error correction for robust shortwave exchanges. These legacy formats declined primarily due to their analog nature, which imposed slow transmission rates—often minutes per image—making them inefficient compared to emerging digital technologies. By the 1990s, and provided instantaneous, high-resolution alternatives for , , and , rendering radiofax obsolete for most professional uses outside niche applications. As of 2025, no active legacy variants persist beyond standardized formats like WEFAX, but software emulations such as MultiMode and FLDigi allow hobbyists to recreate and decode historical radiofax signals, including Finch and Wirephoto styles, using sound card interfaces for educational shortwave listening. SSTV tools like MMSSTV further preserve the analog-to-digital transition, fostering community experiments on amateur bands.

Stations and Operations

Major Global Stations

Major global radiofax stations primarily broadcast weather charts for maritime navigation, utilizing the WEFAX on high-frequency () bands to reach ships at sea. These transmissions, operating continuously or near-continuously, provide essential data such as surface analyses, wind and wave forecasts, , and ice charts, supporting safe passage in remote ocean areas. While weather-related content dominates, a small fraction includes specialized transmissions like newspaper editions from . Frequencies typically fall within the 2-22 MHz range, with most in the 4-16 MHz HF bands, and transmitter powers ranging from 1 to 10 kW to ensure reliable propagation over long distances. In the United States, the National Oceanic and Atmospheric Administration (NOAA) operates four key stations through U.S. Coast Guard facilities in its Weather Radiofax network, delivering 24/7 weather charts tailored to regional marine needs. The station at Point Reyes, California (call sign NMC), transmits on 4346 kHz, 8682 kHz, 12786 kHz, 17151.2 kHz, and 22527 kHz, focusing on Pacific surface analyses and forecasts. Belle Chasse, Louisiana (NMG), uses 4317.9 kHz, 8503.9 kHz, 12789.9 kHz, and 17146.4 kHz for Gulf of Mexico and Atlantic coverage, including tropical cyclone warnings. Marshfield, Massachusetts (NMF), broadcasts via 4235 kHz, 6340.5 kHz, 9110 kHz, and 12750 kHz, emphasizing North Atlantic wind/wave data and ice charts. Kodiak, Alaska (NOJ), operates on 2054 kHz, 4298 kHz, 8459 kHz, and 12412.5 kHz to serve Arctic routes with sea ice and satellite imagery. Additionally, the Department of Defense operates the Honolulu, Hawaii station (KVM70) on 9982.5 kHz, 11090 kHz, and 16135 kHz, covering the central Pacific with equatorial forecasts. These stations maintain round-the-clock schedules without reported consolidations as of November 2025. Internationally, stations from multiple nations enhance global coverage, particularly in the Pacific, Atlantic, and Oceans. Japan's Meteorological Agency runs JMH in on 3622.5 kHz, 7795 kHz, and 13988.5 kHz for comprehensive North Pacific weather maps, while JFX in transmits on 4274 kHz, 8658 kHz, 13074 kHz, 16907.5 kHz, and 22559.6 kHz (updated 2025) for southern regional data including sea surface temperatures. Australia's operates VMC in Charleville on 2628 kHz, 5100 kHz, 11030 kHz, 13920 kHz, and 20469 kHz, supplying and prognoses. In , Germany's (DWD) from Hamburg/Pinneberg (DDH3/DDK) uses 3855 kHz, 7880 kHz, and 13882.5 kHz at 10 kW for North Atlantic and Baltic analyses. Russia's RBW in broadcasts on 5336 kHz, 6446 kHz, 7908.8 kHz, 8444 kHz, and 10130 kHz, prioritizing ice charts and northern sea routes. Chile's service includes CBV in on 4228 kHz, 8677 kHz, and 17146.4 kHz for southeastern Pacific forecasts, and CBM in on 4322 kHz and 8696 kHz for sub-Antarctic coverage. China's XSQ in operates on 4199.75 kHz, 8412.5 kHz, 12629.25 kHz, and 16826.25 kHz, extending reach into the with updates. A notable non-weather use persists with Japan's agency, the sole remaining provider of radiofax newspaper transmissions, active as of mid-2025 on 16971 kHz from (call sign JJC). These broadcasts deliver full editions in and English at scheduled times (e.g., 0200 UTC evening edition, 0300 UTC ), serving Pacific fleets with , sports, and navigational warnings at 60 lines per minute—contrasting the standard 120 lines per minute for weatherfax. This represents less than 5% of global radiofax activity, underscoring the medium's primary role in .

Operational Practices and Equipment

Radiofax broadcast practices follow fixed schedules to ensure reliable delivery of weather charts and forecasts to maritime users. For instance, the (NWS) operates transmissions through U.S. stations, with charts disseminated at intervals ranging from every 15 to 60 minutes depending on the product and region, such as surface analyses every 6 hours and specialized forecasts more frequently. These schedules are coordinated internationally to cover global sea areas, with redundancy achieved by broadcasting the same content across multiple high-frequency (HF) bands to account for varying conditions influenced by time of day and ionospheric activity. In cases of urgent weather events, such as tropical cyclones expected within four days, manual interventions allow for unscheduled or accelerated transmissions, including 3-hour interval updates during active storms. Transmitter equipment at major stations, like those operated by the NWS and , relies on automated systems for efficiency. Images from meteorological data sources are input via computers connected to facsimile scanners, which convert digital charts into analog signals for onto HF carriers. These systems incorporate HF amplifiers to achieve the necessary power levels—typically 2.5 to 10 kW—for long-range , along with built-in monitoring tools to assess signal quality, fidelity, and transmission continuity in . Reception on the user end, particularly in settings, utilizes HF single-sideband () radios interfaced with dedicated decoders. Equipment such as the Icom M803 , certified for non-SOLAS vessels, integrates with external interfaces to demodulate and print incoming signals. For cost-effective setups, PC-based decoders employing standard s—coupled with like those supporting WEFAX protocols—allow decoding via a connected to an , outputting to or inkjet printers for hard copies or displays. Basic configurations, including a used , adapter, and printer, remain accessible under $500 in 2025. Maintenance of radiofax networks involves adherence to International Telecommunication Union (ITU) regulations for , where HF bands (typically 3-30 MHz) are allocated to the fixed and mobile services under Article 5 of the Radio Regulations, requiring coordination among nations to prevent interference. Contingencies for solar flares, which disrupt HF through ionospheric disturbances, include predefined frequency hopping to less-affected bands and fallback to voice broadcasts or satellite services when available. Ship officers receive mandatory training under the Global Maritime Distress and Safety System (GMDSS), covering HF radio operations including radiofax reception, as part of SOLAS Chapter IV requirements to ensure competency in distress and safety communications. Looking ahead, radiofax operations face a gradual transition toward digital HF alternatives, such as those defined in MIL-STD-188-110C for data modems, enabling higher-speed image and text transmission over HF channels. However, analog radiofax remains mandated under SOLAS for GMDSS compliance in remote sea areas (A3 and A4), where satellite coverage is limited, ensuring continued reliability for essential weather dissemination in 2025 and beyond.

References

  1. [1]
    Maritime Fax Transmissions - HFUnderground
    Oct 23, 2022 · Radiofax is primarily used worldwide for the dissemination of weather charts, satellite weather images, and forecasts to ships at sea.
  2. [2]
    Fax Machines - Engineering and Technology History Wiki
    Jun 14, 2018 · The basic concept of a facsimile, or fax, machine–a machine that electrically transmits an image–has not changed since 1843.<|control11|><|separator|>
  3. [3]
    Radio Facsimile - The Radio Historian
    The first rudimentary fax patent was issued in Paris in 1843 and used a swinging pendulum to draw the image. Englishman Edwin Belin first demonstrated his ...
  4. [4]
    Weather Fax Charts versus Electronically Derived GRIBs
    Oct 31, 2023 · Fax Charts are weather charts and other graphic images such as weather satellite imagery broadcast and received by many vessels at sea using a ...
  5. [5]
    Radiofax Hardware Companies - National Weather Service
    Radiofax, also known as HF FAX, radiofacsimile or weatherfax, is a means of broadcasting graphic weather maps and other graphic images via HF radio.Missing: definition | Show results with:definition
  6. [6]
    [PDF] INTERNATIONAL STANDARD ISO 9876
    Mar 15, 2015 · index of cooperation. IOC value of the index of cooperation, M, is defined as follows: M LF. = /π. whereL is the length of the scanning line ...
  7. [7]
    Technical characteristics of Voice and Fax HF transmissions - BoM
    Modulation: FSK (F3C) · Emission code: 3K00F3C · FSK Carrier: 1900 Hz · Shift: White +400 Hz, Black -400 Hz · Scan line frequency: 2 lines per second (120 lines per ...Missing: radiofax | Show results with:radiofax
  8. [8]
    [PDF] Facsimile — Radiofax - SSTV handbook
    Facsimile (from latin facere – make and simile – similar) is one of the oldest com- munication modes and it is used for an image transmission.
  9. [9]
    [PDF] Marine Fact Sheet - National Hurricane Center - NOAA
    Oct 17, 2016 · All radiofax broadcasts of NWS products employ a radiofax signal of 120 lines per-minute. (LPM) and an Index-of-Cooperation (IOC) of 576.
  10. [10]
    History - HF-Fax
    1911The first amplitude modulator for fax machines is patented, permitting transmission via telephone lines. 1913Edouard Belin's Belinograph. 1922 the first ...
  11. [11]
    The Fax -- History and Capabilities - Edinformatics
    As a designer for the Radio Corporation of America (RCA), in 1924, Richard H. Ranger invented the wireless photoradiogram, or transoceanic radio facsimile ...
  12. [12]
    Notes - Project MUSE - Johns Hopkins University
    Ernst F. W. Alexanderson, “Transmission of Pictures,” U.S. Patent No. ... 1931, assigned to General Electric; Otto. Böhm, “Signaling by Frequency ...
  13. [13]
    Print the News, Right In Your Home! - Smithsonian Magazine
    Apr 17, 2012 · W.G.H. Finch, the inventor of the radio facsimile system. Mr. Finch (pictured above) would later invent the first color fax machine in 1946.
  14. [14]
    Finch Facsimile Transmitter, 1938-1940 - The Henry Ford
    From 1938-1940, the Detroit News experimented with a domestic radio-facsimile subscription service. This transmitter converted images and text into electrical ...
  15. [15]
    “Just the (radio) FAX, Ma'am” | Nuts & Volts Magazine
    The first radio facsimile system was patented in 1905, and its earliest application was transmitting weather maps and other data to ships at sea (a practice ...
  16. [16]
    USSR Luna-9 sends moon photos - UPI Archives
    USSR Luna-9 sends moon photos. By United Press International. February 04, 1966 ... Lovell borrowed a facsimile machine which is used by news papers to receive ...
  17. [17]
    KD2BD: Revisiting Slow-Scan Television - QSL.net
    Slow-Scan Television is a method of picture transmission invented by Amateur Radio Operator Copthorne MacDonald in 1957.
  18. [18]
    [PDF] Worldwide Marine Radiofacsimile Broadcast Schedules
    Mar 7, 2025 · This document provides worldwide marine radiofacsimile broadcast schedules. Ships are urged to report weather at 0000, 0600, 1200, and 1800 UTC ...Missing: definition | Show results with:definition
  19. [19]
    Marine Radiofax Charts - National Weather Service
    Marine Radiofax Charts ; Marine Text Forecasts · Coastal/Great Lakes Forecasts · Offshore Forecasts ; Radiofax Charts · Marine Radiofax Charts · Weather Charts on ...New Orleans · NW ATLANTIC (Boston/NMF) · Pt. Reyes, CAMissing: modern 2020s UK 2024
  20. [20]
    HF Radio Communications - Space Weather Prediction Center - NOAA
    Another type of space weather, the Radiation Storm caused by energetic solar protons, can also disrupt HF radio communication. The protons are guided by ...Missing: weatherfax | Show results with:weatherfax
  21. [21]
    Space weather impact on radio communication and navigation
    Jan 26, 2024 · Space weather can cause significant disruptions to modern communications and navigation systems, leading to increased safety risks, economic losses, and ...Space Weather Impact On... · 3. Discussion · AbstractMissing: weatherfax usage
  22. [22]
    A Look Back at the Radio Newspaper of the Air - Radio World
    Oct 1, 2021 · Finch envisioned the delivery of newspapers to the public via radio facsimile. The Finch system circumvented RCA's patents in several ways.
  23. [23]
    The Forgotten 1930s Tech That Delivered Newspapers via Radio
    Jan 29, 2015 · Almost entirely forgotten today, it was a technology that could deliver newspapers over the radio waves, then print them instantly right in your home.
  24. [24]
    Radiofax: First Kyodo News Morning Edition of 2025
    Jan 1, 2025 · First 2025 morning edition of Kyodo News: “Happy New Year. We wish all ships a safe voyage.” Kyodo News is the only news agency in the world that sends news to ...
  25. [25]
    Radiofax - Wikipedia
    Radiofacsimile, radiofax or HF fax is an analogue mode for transmitting grayscale images via high frequency (HF) radio waves.Missing: principles | Show results with:principles
  26. [26]
    Luna 9: The First Lunar Landing | Drew Ex Machina
    Feb 3, 2016 · Soviet scientists and engineers had the chance to beat their American counterparts to a lunar landing using their new E-6 spacecraft.
  27. [27]
    [PDF] observations of the russian moon probe luna 9
    Fig. 4. Photograph of the lunar surface as received from Luna 9 on 1966 Febr. 4 between 15h 30m and 16h 55m U.T. A part of the protective.
  28. [28]
    [PDF] The Characterization of Facsimile Camera Systems for Lunar and ...
    Basically, facsimile cameras consist of a telephotometer (a point detector with a lens) which is mechanically scanned across the image. A variety of.
  29. [29]
    Wirephoto - Wikipedia
    Wirephoto, telephotography or radiophoto is the sending of photographs by telegraph, telephone or radio.
  30. [30]
    Kyodo News Radiofax: Japanese Disaster FM Stations and a Lack ...
    Apr 22, 2024 · I received today by radiofax in Porto Alegre the morning edition of Kyodo News and the front page news is that, due to lack of personnel, the ...Missing: Pacific | Show results with:Pacific
  31. [31]
    [PDF] 0 - Navy Radio
    transmitter, to audio-frequency-shift facsimile signals of 1500 to 2300 Hz suitable for modulating a radiophone transmitter. A block diagram of ...
  32. [32]
    Technical characteristics of Voice and Fax HF transmissions - BoM
    Scan line stability: Within 5 parts in 1,000,000; Index of co-operation: 576; Scanning line density: 3.8 lines per millimetre (96 lines per inch); Picture ...Missing: radiofax IOC
  33. [33]
    Sending WEFAX transmissions with FLDigi
    Aug 17, 2023 · A popular reception target for those new to amateur radio and HF data in general are the various weather fax transmissions that are sent ...
  34. [34]
    Receiving Weather Fax and Weather Satellite Images With Your Macintosh
    ### Summary: Receiving and Decoding Weather Fax Images
  35. [35]
    How to Receive Marine Radiofax Charts - R a n o u s - WordPress.com
    Jul 3, 2015 · From the top menu choose Op Mode > WEFAX > WEFAX-IOC576. In the button bar just above the waterfall display confirm that LPM is set to 120, ...Missing: GNU generate
  36. [36]
    Radiofax - LittleCamels.com
    The programme I use for decoding Radiofax transmissions is SeaTTY, a software that decodes the audio signal coming from the line-out of my receiver to the mic- ...
  37. [37]
    [PDF] Basics to decoding WEFAX using an RSP and SDRuno - SDRplay
    Black Cat HF Weather Fax is a program that decodes WEFAX (Weatherfax, HF-FAX, Radiofax, and Weather Facsimile) transmissions sent from fixed locations around ...
  38. [38]
    Radio: RadioFax/HF Fax Reception on KiwiSDR with kiwifax.py
    Jan 13, 2019 · Instead, with the advent of sound-card based decoding software, radiofax can be decoded using software such as Fldigi (free), MultiPSK (limited ...
  39. [39]
    Alden's New Marine Fax Recorder Receives Weather Charts As Well
    Weather charts and Navtex/ RTTY messages are printed on crisp, white thermal paper. The Marinefax meets the international World Meteorological Organization ...Missing: historical | Show results with:historical
  40. [40]
    [PDF] I I I 1 I I l I I I I I I l I I I i - NASA Technical Reports Server (NTRS)
    (WEFAX} has been studied, with particular reference to orbital and meteorological factors. The study included an analysis of prospective. WEFAX customers. It ...
  41. [41]
    [PDF] Handbook on Use of Radio Spectrum for Meteorology - ITU
    facsimile (WEFAX). However, the unreliable nature of HF has caused a transition of many such systems to satellite transmission. Finally, it should also be ...
  42. [42]
    FAQ - NOAASIS
    What is the difference between WEFAX, LRIT and HRIT/EMWIN? At the CGMS XXVIII meeting in October 2000, NOAA announced that the analogue Weather Facsimile (WEFAX) ...Missing: usage | Show results with:usage
  43. [43]
    [PDF] THE AUTOMATIC PICTURE TRANSMISSION (APT) TV CAMERA ...
    The APT system is for automatic, real-time picture transmission of cloud cover from a satellite to ground stations, using a vidicon camera.
  44. [44]
    [PDF] Educators Guide for Building and Operating Environmental Satellite ...
    The Automatic Picture Transmission system (APT) was developed to help alleviate this problem by making it possible for forecast centers in any part of the ...Missing: HF radiofax
  45. [45]
    Automatic Picture Transmission (APT) - Signal Identification Wiki
    Sep 7, 2025 · Automatic Picture Transmission (APT), also known as NOAA-GEOSAT, is an analog image transmission mode used to by the NOAA weather satellites.
  46. [46]
    Retrotechtacular: Electronic Publishing In The 1930s - Hackaday
    Dec 22, 2015 · Radio facsimile newspaper technology was introduced to the public at the 1939 World's Fair at two different booths. One belonged to an inventor ...
  47. [47]
    Wire Photography and Transatlantic Visual Culture
    Beginning in the 1920s, wire photography services used a technology similar to a fax machine to send news pictures across the Atlantic much faster than ever ...Missing: 1950s | Show results with:1950s
  48. [48]
    Fun: Decoding UPI 16-S Wirephoto Transmission | Gough's Tech Zone
    Jan 25, 2025 · ... aspect ratio needed some correction, but it seems a ... Radiofax News: BMF Confirmed Offline, VMC/VMW Transmission Fault & Radiofax Status.
  49. [49]
    90 years since AP Wirephoto revolutionized news technology
    Ninety years ago, on Jan. 1, 1935, The Associated Press, using groundbreaking technology, marked an industry first: sending a photograph on the wire.Missing: RCA 1940s facsimile
  50. [50]
    Luna 9 - Wikipedia
    On 3 February 1966, the Luna 9 spacecraft became the first spacecraft to achieve a soft landing on the Moon and return imagery from its surface.
  51. [51]
    Image Communication on Short Waves – SSTV, WEFAX, HamDRM
    I'd like to introduce the e-book for ham radio operators and radio listeners interested in special communication modes for image transmission – SSTV, radio ...
  52. [52]
    News Via Fax Machine: A Technology That Failed Twice - Tedium
    Nov 7, 2019 · Finch created a system which used specialized paper to print dots onto a sheet of paper, line by line, as they came over the airwaves. In 1939, ...
  53. [53]
    VMC & VMW Radio Fax Schedule - The Bureau of Meteorology
    Jul 1, 2017 · *The following charts are repeat broadcasts on 11030 kHz only via a directional aerial pointing from Charleville (VMC) towards Tasmania.
  54. [54]
    https://www.dwd.de/EN/specialusers/shipping/broadcast_en/broadcast_fax_112016.pdf
  55. [55]
    Kyodo News Radiofax English Edition: June 13, 2025
    Jun 15, 2025 · Today's Kyodo News English Edition radiofax, received in Porto Alegre, Brazil, 16970 kHz (USB):. Israel attacks Iran's nuclear and missile sites ...
  56. [56]
    Marine Weather Broadcasts from the USCG
    The NWS radiofax program prepares high seas weather maps via four U.S. Coast Guard sites: Boston, New Orleans, Pt. Reyes, and Kodiak and the Defense Department ...
  57. [57]
    https://www.ebay.com/shop/fax-weather?_nkw=fax%2Bweather
  58. [58]
    Fax Weather - eBay
    4.5 3K · Free deliveryPrice ; Furuno FAX-408 Weather Facsimile Receiver Made in japan · $499.00 ; Weather Fax 2000 USB Version For Windows · $155.00 ; FURUNO FAX-5 WEATHER FASCIMILE ...
  59. [59]
    Managing the radio-frequency spectrum for the world - ITU-R
    ITU-R is the global agency managing the radio-frequency spectrum and satellite orbit resources, using the Radio Regulations to share spectrum.Missing: radiofax | Show results with:radiofax
  60. [60]
    [PDF] national weather service instruction 10-2301
    Apr 18, 2024 · The purpose of the training is to provide the ship's officers with practical assistance in observing techniques and use of the ...
  61. [61]
    MIL-STD-188-110C | Wideband HF Data Modems | 3 to 24 kHz
    MIL-STD-188-110C further improves HF data transmission with wideband HF data modems ranging from 3 to 24 kHz in 3 kHz steps, as described in Appendix D.Missing: future trends
  62. [62]
    IMO Sub-Committee on Navigation, Communications, Search ... - DNV
    May 23, 2025 · NCSR 12 finalized draft SOLAS amendments to enable digital data exchange over VHF (VDES), advanced the framework for the digital broadcasting of ...Missing: shift | Show results with:shift