Slow-scan television
Encyclopedia
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
operators, to transmit and receive static pictures via radio in 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...
or color.
A technical term for SSTV is narrowband television. Broadcast
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
television requires 6 MHz wide channels, because it transmits 25 or 30 picture frames per second (in the NTSC
NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
, PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
or SECAM
SECAM
SECAM, also written SÉCAM , is an analog color television system first used in France....
color systems), but SSTV usually only takes up to a maximum of 3 kHz of bandwidth. It is a much slower method of still picture transmission, usually taking from about eight seconds to a couple of minutes, depending on the mode used, to transmit one image frame.
Since SSTV systems operate on voice frequencies
Voice frequency
A voice frequency or voice band is one of the frequencies, within part of the audio range, that is used for the transmission of speech.In telephony, the usable voice frequency band ranges from approximately 300 Hz to 3400 Hz...
, amateurs use it on shortwave
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
(also known as HF
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
by amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
operators), VHF
Very high frequency
Very high frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency...
and UHF
Ultra high frequency
Ultra-High Frequency designates the ITU Radio frequency range of electromagnetic waves between 300 MHz and 3 GHz , also known as the decimetre band or decimetre wave as the wavelengths range from one to ten decimetres...
radio.
Concept
The concept of SSTV was introduced by Copthorne Macdonald in 1957–1958. He developed the first SSTV system using an electrostatic monitor and a vidicon tube. In those days it seemed sufficient to use 120 lines and about 120 pixels per line to transmit a black-and-white still picture within a 3 kHz phone channel. First live tests were performed on the 11 Meter ham band - which was later given to the CB service in the US.Early usage in space exploration
Luna 3
The Soviet space probe Luna 3 of 1959 was the third space probe to be sent to the neighborhood of the Moon, and this mission was an early feat in the spaceborne exploration of outer space...
.
The first space television system was called Seliger-Tral-D and was used aboard Vostok
Vostok
Vostok may refer to one of the following.Spaceflight*The Soviet Vostok programme of human spaceflight.*The Vostok spacecraft used in that programme and also the basis of a reconnaissance satellite.*The Vostok rocket, used to launch the Vostok spacecraft....
. Vostok was based on an earlier videophone
Videophone
A videophone is a telephone with a video screen, and is capable of full duplex video and audio transmissions for communication between people in real-time...
project which used two cameras, with persistent LI-23 iconoscope
Iconoscope
The Iconoscope was the name given to an early television camera tube in which a beam of high-velocity electrons scans a mosaic of photoemissive isolated granules...
tubes. Its output was 10 frames per second at 100 lines per frame video signal.
- The Seliger system was tested during the 1960 launches of the VostokVostokVostok may refer to one of the following.Spaceflight*The Soviet Vostok programme of human spaceflight.*The Vostok spacecraft used in that programme and also the basis of a reconnaissance satellite.*The Vostok rocket, used to launch the Vostok spacecraft....
capsule, including Sputnik 5Sputnik 5Korabl-Sputnik 2 , also known as Sputnik 5 in the West, was a Soviet artificial satellite, and the third test flight of the Vostok spacecraft. It was the first spaceflight to send animals into orbit and return them safely back to Earth...
, containing the space dogs Belka and StrelkaStrelkaStrelka, Russian for "little arrow" may refer to one of the following:*Strelka , one of the Russian space dogs*Strelka, a tip on a confluence or divergence of two rivers or distributaries, particularly:...
, whose images are often mistaken for the dog LaikaLaikaLaika was a Soviet space dog that became the first animal to orbit the Earth – as well as the first animal to die in orbit.As little was known about the impact of spaceflight on living creatures at the time of Laika's mission, and the technology to de-orbit had not yet been developed, there...
and the 1961 flight of Yuri GagarinYuri GagarinYuri Alekseyevich Gagarin was a Soviet pilot and cosmonaut. He was the first human to journey into outer space, when his Vostok spacecraft completed an orbit of the Earth on April 12, 1961....
, the first man in space on Vostok 1Vostok 1Vostok 1 was the first spaceflight in the Vostok program and the first human spaceflight in history. The Vostok 3KA spacecraft was launched on April 12, 1961. The flight took Yuri Gagarin, a cosmonaut from the Soviet Union, into space. The flight marked the first time that a human entered outer...
. - Vostok 2Vostok 2Vostok 2 was a Soviet space mission which carried cosmonaut Gherman Titov into orbit for a full day in order to study the effects of a more prolonged period of weightlessness on the human body...
and thereafter used an improved 400-line television system referred to as TopazTopazTopaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO42. Topaz crystallizes in the orthorhombic system and its crystals are mostly prismatic terminated by pyramidal and other faces.-Color and varieties:...
. - A second generation system (KrechetKrechetThe Krechet-94 is a space suit model developed for lunar excursion during the Soviet manned lunar program. It was designed by NPP Zvezda. Development began in 1967, concurrently with the Orlan suit for microgravity spacewalks...
, incorporating docking views, overlay of docking data, etc.) was introduced after 1975.
A similar concept, also named SSTV, was used on Faith 7
Mercury-Atlas 9
Mercury-Atlas 9 was the final manned space mission of the U.S. Mercury program, launched on May 15, 1963 from Launch Complex 14 at Cape Canaveral, Florida. The spacecraft, named Faith 7, completed 22 Earth orbits before splashing down in the Pacific Ocean, piloted by astronaut Gordon Cooper, then...
as well as on the early years of the NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
Apollo
Project Apollo
The Apollo program was the spaceflight effort carried out by the United States' National Aeronautics and Space Administration , that landed the first humans on Earth's Moon. Conceived during the Presidency of Dwight D. Eisenhower, Apollo began in earnest after President John F...
program. The Faith 7 camera transmitted one frame every two seconds.
Apollo TV camera
Television cameras used on the Apollo Project's missions varied in design, with image quality improving significantly with each design. A camera was carried in the Apollo Command Module...
s used SSTV to transmit images from inside Apollo 7
Apollo 7
Apollo 7 was the first manned mission in the American Apollo space program, and the first manned US space flight after a cabin fire killed the crew of what was to have been the first manned mission, AS-204 , during a launch pad test in 1967...
, Apollo 8
Apollo 8
Apollo 8, the second manned mission in the American Apollo space program, was the first human spaceflight to leave Earth orbit; the first to be captured by and escape from the gravitational field of another celestial body; and the first crewed voyage to return to Earth from another celestial...
, and Apollo 9
Apollo 9
Apollo 9, the third manned mission in the American Apollo space program, was the first flight of the Command/Service Module with the Lunar Module...
, as well as the Apollo 11
Apollo 11
In early 1969, Bill Anders accepted a job with the National Space Council effective in August 1969 and announced his retirement as an astronaut. At that point Ken Mattingly was moved from the support crew into parallel training with Anders as backup Command Module Pilot in case Apollo 11 was...
Lunar Module
Apollo Lunar Module
The Apollo Lunar Module was the lander portion of the Apollo spacecraft built for the US Apollo program by Grumman to carry a crew of two from lunar orbit to the surface and back...
television from the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
. NASA had taken all the original tapes and erased them for use on subsequent missions; however, the Apollo 11 Tape Search and Restoration Team formed in 2003 tracked down the highest quality footage among the converted recordings of the first broadcast, pieced together the best footage, then contracted a specialist film restoration company to enhance the degraded black-and-white film and convert it into digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
format for archival records
Archive
An archive is a collection of historical records, or the physical place they are located. Archives contain primary source documents that have accumulated over the course of an individual or organization's lifetime, and are kept to show the function of an organization...
.
- The SSTV system used in NASANASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's early Apollo missions transferred ten frames per second with a resolution of 320 frame lines using less bandwidth than a normal TV transmission. - The early SSTV systems used by NASA differ significantly from the SSTV systems currently in use by amateur radio enthusiasts today.
Evolution
Commercial systems started appearing in the United States in 1970, after the FCCFederal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
had legalized the use of SSTV for advanced level
Amateur radio licensing in the United States
In the United States, amateur radio licensing is governed by the Federal Communications Commission under strict federal regulations. Licenses to operate amateur stations for personal use are granted to individuals of any age once they demonstrate an understanding of both pertinent FCC regulations...
amateur radio operators in 1968.
SSTV originally required quite a bit of specialized equipment. Usually there was a scanner or camera, a modem to create and receive the characteristic audio howl, and a cathode ray tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
from a surplus radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
set. The special cathode ray tube would have "long persistence" phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
s that would keep a picture visible for about ten seconds.
The modem
Modem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...
would generate audio tones between 1200 and 2300 Hz from picture signals, and picture signals from received audio tones. The audio would be attached to a radio receiver
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
and transmitter
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
.
Current systems
A modern system, having gained ground since the early 1990s, uses a personal computerPersonal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
and special software in place of much of the custom equipment. The sound card
Sound card
A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...
of a PC, with special processing software, acts as a modem. The computer screen provides the output. A small digital camera
Digital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
or digital photos provide the input.
Modulation
SSTV uses analogue frequency modulationFrequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
, in which every different value of brightness
Brightness
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target...
in the image gets a different audio frequency. In other words, the signal frequency shifts up or down to designate brighter or darker pixels, respectively. Color is achieved by sending the brightness of each color component (usually red, green and blue) separately. This signal can be fed into an SSB
Single-sideband modulation
Single-sideband modulation or Single-sideband suppressed-carrier is a refinement of amplitude modulation that more efficiently uses electrical power and bandwidth....
transmitter, which in part modulates the carrier wave
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...
.
There are a number of different modes of transmission, but the most common ones are Martin M1 (popular in Europe) and Scottie S1 (used mostly in the USA). Using one of these, an image transfer takes 114 (M1) or 110 (S1) seconds. Some black and white modes take only 8 seconds to transfer an image.
Header
A calibration header is sent before the image. It consists of a 300-millisecond leader tone at 1900 Hz, a 10 ms break at 1200 Hz, another 300-millisecond leader tone at 1900 Hz, followed by a digital VIS (vertical interval signaling) code, identifying the transmission mode used. The VIS consists of bitBit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s of 30 milliseconds in length. The code starts with a start bit at 1200 Hz, followed by 7 data bits (LSB
Least significant bit
In computing, the least significant bit is the bit position in a binary integer giving the units value, that is, determining whether the number is even or odd. The lsb is sometimes referred to as the right-most bit, due to the convention in positional notation of writing less significant digits...
first; 1100 Hz for 1, 1300 Hz for 0). An even parity bit
Parity bit
A parity bit is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd. Parity bits are used as the simplest form of error detecting code....
follows, then a stop bit at 1200 Hz. For example, the bits corresponding the decimal numbers 44 or 32 imply that the mode is Martin M1, whereas the number 60 represents Scottie S1.
Scanlines
A transmission consists of horizontal lines, scanned from left to right. The color components are sent separately one line after another. The color encoding and order of transmission can vary between modes. Most modes use an RGB color modelRGB color model
The RGB color model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors...
; some modes are black-and-white, with only one channel being sent; other modes use a YC color model, which consists of luminance
Luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square...
(Y) and chrominance
Chrominance
Chrominance is the signal used in video systems to convey the color information of the picture, separately from the accompanying luma signal . Chrominance is usually represented as two color-difference components: U = B' − Y' and V = R' − Y'...
(R-Y and B-Y). The modulating frequency changes between 1500 and 2300 Hz, corresponding to the intensity (brightness
Brightness
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target...
) of the color component. The modulation is analogue, so even though the horizontal resolution is often defined as 256 or 320 pixels, they can be sampled using any rate. The image aspect ratio
Aspect ratio (image)
The aspect ratio of an image is the ratio of the width of the image to its height, expressed as two numbers separated by a colon. That is, for an x:y aspect ratio, no matter how big or small the image is, if the width is divided into x units of equal length and the height is measured using this...
is conventionally 4:3. Lines usually end in a 1200 Hz horizontal synchronization pulse of 5 milliseconds (after all color components of the line have been sent); in some modes, the synchronization pulse lies in the middle of the line.
Modes
Below is a table of some of the most common SSTV modes and their differences. These modes share many properties, such as synchronization and/or frequencies and grey/color level correspondence. Their main difference is the image quality, which is proportional to the time taken to transfer the image and in the case of the AVT modes, related to synchronous data transmission methods and noise resistance conferred by the use of interlace.| Family | Developer | Name | Color | Time | Lines |
|---|---|---|---|---|---|
| AVT | Ben Blish / AEA | 8 | BW or 1 of R, G, or B | 8 s | 128×128 |
| 16w | BW or 1 of R, G, or B | 16 s | 256×128 | ||
| 16h | BW or 1 of R, G, or B | 16 s | 128×256 | ||
| 32 | BW or 1 of R, G, or B | 32 s | 256×256 | ||
| 24 | RGB | 24 s | 128×128 | ||
| 48w | RGB | 48 s | 256×128 | ||
| 48h | RGB | 48 s | 128×256 | ||
| 104 | RGB | 96 s | 256×256 | ||
| Martin | Martin Emmerson | M1 | RGB | 114 s | 240¹ |
| M2 | RGB | 58 s | 240¹ | ||
| Robot | Robot SSTV | 8 | BW or 1 of R, G or B | 8 s | 120 |
| 12 | YUV YUV YUV is a color space typically used as part of a color image pipeline. It encodes a color image or video taking human perception into account, allowing reduced bandwidth for chrominance components, thereby typically enabling transmission errors or compression artifacts to be more efficiently... |
12 s | 128 luma, 32/32 chroma × 120 | ||
| 24 | YUV YUV YUV is a color space typically used as part of a color image pipeline. It encodes a color image or video taking human perception into account, allowing reduced bandwidth for chrominance components, thereby typically enabling transmission errors or compression artifacts to be more efficiently... |
24 s | 128 luma, 64/64 chroma × 120 | ||
| 32 | BW or 1 of R, G or B | 32 s | 256 × 240 | ||
| 36 | YUV YUV YUV is a color space typically used as part of a color image pipeline. It encodes a color image or video taking human perception into account, allowing reduced bandwidth for chrominance components, thereby typically enabling transmission errors or compression artifacts to be more efficiently... |
36 s | 256 luma, 64/64 chroma × 240 | ||
| 72 | YUV YUV YUV is a color space typically used as part of a color image pipeline. It encodes a color image or video taking human perception into account, allowing reduced bandwidth for chrominance components, thereby typically enabling transmission errors or compression artifacts to be more efficiently... |
72 s | 256 luma, 128/128 chroma × 240 | ||
| Scottie | Eddie Murphy | S1 | RGB | 110 s | 240¹ |
| S2 | RGB | 71 s | 240¹ |
The mode family called AVT (for Amiga Video Transceiver) was originally designed by Ben Blish (N4EJI, then AA7AS) for a custom modem attached to an Amiga computer, which was eventually marketed by AEA corporation.
The Scotty and Martin modes were originally implemented as ROM enhancements for the Robot corporation SSTV unit. The exact line timings for the Martin M1 mode are given in this reference.
The Robot SSTV modes were designed by Robot corporation for their own SSTV unit.
All four sets of SSTV modes are now available in various PC-resident SSTV systems and no longer depend upon the original hardware.
AVT
AVT is an abbreviation of "Amiga Video Transceiver", software and hardware modem originally developed by "Black Belt Systems" (USA) around 1990 for the AmigaAmiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
home computer popular all over the world before the IBM PC
IBM PC compatible
IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...
family gained sufficient audio quality with the help of special sound card
Sound card
A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...
s.
These AVT modes differ radically from the other modes mentioned above, in that they have no per-line horizontal synchronization pulse but instead use the standard VIS vertical signal to identify the mode, followed by a frame-leading digital pulse train which pre-aligns the frame timing by counting first one way and then the other, allowing the pulse train to be locked in time at any single point out of 32 where it can be resolved or demodulated successfully, after which they send the actual image data, in a fully synchronous and typically interlaced mode.
Interlace, no dependence upon sync, and interline reconstruction gives the AVT modes a better noise resistance than any of the other SSTV modes. Full frame images can be reconstructed with reduced resolution even if as much as 1/2 of the received signal was lost in a solid block of interference or fade because of the interlace feature. For instance, first the odd lines are sent, then the even lines. If a block of odd lines are lost, the even lines remain, and a reasonable reconstruction of the odd lines can be created by a simple vertical interpolation, resulting in a full frame of lines where the even lines are unaffected, the good odd lines are present, and the bad odd lines have been replaced with an interpolation. This is a significant visual improvement over losing a non-recoverable contiguous block of lines in a non-interlaced transmission mode. Interlace is an optional mode variation, however without it, much of the noise resistance is sacrificed. Older computers sometimes needed to do this in order to make up for an inability to precisely match the synchronous timing of the frame over long periods.
The AVT modes are mainly used in 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...
and the USA. There is a full set of them in terms of black and white, color, and scan line counts of 128 and 256. Color bars and greyscale bars may be optionally overlaid top and/or bottom, but the full frame is available for image data unless the operator chooses otherwise.
Frequencies
Using a receiver capable of demodulating single-sideband modulationSingle-sideband modulation
Single-sideband modulation or Single-sideband suppressed-carrier is a refinement of amplitude modulation that more efficiently uses electrical power and bandwidth....
, SSTV transmissions can be heard on the following frequencies:
| Band | Frequency | Sideband |
|---|---|---|
| 80 meters | 3845 kHz (3730 in Europe) | LSB |
| 40 meters | 7170 kHz (7043 in Europe) | LSB |
| 20 meters | 14,230 kHz | USB |
| 15 meters | 21,340 kHz | USB |
| 10 meters | 28,680 kHz | USB |
Media
In popular culture
The video game Portal, in an internet update of the program files three years after its original release, provided in-game radio objects, whose sound effects became part of an alternate reality gameAlternate reality game
An alternate reality game is an interactive narrative that uses the real world as a platform, often involving multiple media and game elements, to tell a story that may be affected by participants' ideas or actions....
-style analysis by fans of the game hinting at a sequel of the game - the effects included Morse code
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
strings that implied the restarting of a computer system, and could be decoded as SSTV images from a grainy video. These images included further hints of a BBS phone number that when accessed, provided a large number of ANSI
Ansi
Ansi is a village in Kaarma Parish, Saare County, on the island of Saaremaa, Estonia....
-based images relating to the game and its potential sequel. The sequel, Portal 2
Portal 2
Portal 2 is a first-person puzzle-platform video game developed and published by Valve Corporation. The sequel to the 2007 video game Portal, it was announced on March 5, 2010, following a week-long alternate reality game based on new patches to the original game...
, was later confirmed.
In the aforementioned sequel, Portal 2, more SSTV images are broadcast in Rattman dens. When decoded, these images are pictures concerning elements of the game, such as the Weighted Companion Cube on the moon, all with the Aperture Science logo.
See also
- Amateur televisionAmateur televisionAmateur television is the transmission of Broadcast quality video and audio over the wide range of frequencies of allocated for Radio amateur use. ATV is used for non-commercial experimentation, pleasure and public service events...
- HellschreiberHellschreiberThe 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...
- Narrow-bandwidth televisionNarrow-bandwidth televisionNarrow-bandwidth television is a type of television designed to fit into a low-bandwidth channel, in the extreme case using amateur radio voice frequency channels that only range up to a few kilohertz...
- RadiofaxRadiofaxRadiofax, also known as weatherfax and HF fax , is an analogue mode for transmitting monochrome images. It was the predecessor to slow-scan television...
- RadioteletypeRadioteletypeRadioteletype 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...
- ShortwaveShortwaveShortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
- SSTV repeater
- VideotelephonyVideotelephonyVideotelephony comprises the technologies for the reception and transmission of audio-video signals by users at different locations, for communication between people in real-time....
External links
- Live Slow Scan for Live SSTV from round the world & loads more
- SSTV from the International Space Station lists images received from the International Space station via SSTV
- Image Communication on Short Waves is online free ham radio handbook for SSTV, WEFAX and digital SSTV.
Modem software:
- MMSSTV for Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
- Ham Radio Deluxe for Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
- RX-SSTV for Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
- QSSTV for LinuxLinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
- MultiScan for Mac OS XMac OS XMac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...