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Sluggish-scan tv – Wikipedia

Sluggish-scan tv – Wikipedia

2023-11-13 10:20:09

Picture transmission over radio

SSTV transmissions typically embody station call signs, RST reception experiences, and Amateur radio jargon.

Sluggish-scan tv (SSTV) is an image transmission technique, used primarily by amateur radio operators, to transmit and obtain static photos through radio in monochrome or colour.

A literal time period for SSTV is narrowband television. Analog broadcast tv requires a minimum of 6 MHz huge channels, as a result of it transmits 25 or 30 image frames per second (see ITU analog broadcast standards), however SSTV often solely takes as much as a most of three kHz of bandwidth. It’s a a lot slower technique of nonetheless image transmission, often taking from about eight seconds to a few minutes, relying on the mode used, to transmit one picture body.

Since SSTV programs function on voice frequencies, amateurs apply it to shortwave (also referred to as HF by amateur radio operators), VHF and UHF radio.

Historical past[edit]


The idea of SSTV was launched by Copthorne Macdonald[1] in 1957–58.[2] He developed the primary SSTV system utilizing an electrostatic monitor and a vidicon tube. It was deemed adequate to make use of 120 traces and about 120 pixels per line to transmit a black-and-white nonetheless image inside a 3 kHz phone channel. First reside exams had been carried out on the 11-meter ham band – which was later given to the CB service within the US. Within the Seventies, two types of paper printout receivers had been invented by hams.

Early utilization in house exploration[edit]

Astronaut Gordon Cooper, SSTV transmission from Religion 7

SSTV was used to transmit pictures of the far facet of the Moon from Luna 3.[3]

The primary house tv system was known as Seliger-Tral-D and was used aboard Vostok. Vostok was primarily based on an earlier videophone mission which used two cameras, with persistent LI-23 iconoscope tubes. Its output was 10 frames per second at 100 traces per body video sign.

  • The Seliger system was examined throughout the 1960 launches of the Vostok capsule, together with Sputnik 5, containing the space dogs Belka and Strelka, whose pictures are sometimes mistaken for the canine Laika, and the 1961 flight of Yuri Gagarin, the primary man in house on Vostok 1.
  • Vostok 2 and thereafter used an improved 400-line tv system known as Topaz.
  • A second era system (Krechet, incorporating docking views, overlay of docking knowledge, and so forth.) was launched after 1975.

The same idea, additionally named SSTV, was used on Faith 7,[4] in addition to on the early years of the NASA Apollo program.

  • The Religion 7 digicam transmitted one body each two seconds, with a decision of 320 traces.[4]
NASA slow-scan picture from the Moon

The Apollo TV cameras used SSTV to transmit pictures from inside Apollo 7, Apollo 8, and Apollo 9, in addition to the Apollo 11 Lunar Module tv from the Moon. NASA had taken all the unique tapes and erased them to be used on subsequent missions; nevertheless, the Apollo 11 Tape Search and Restoration Team fashioned in 2003 tracked down the highest-quality movies among the many transformed recordings of the primary broadcast, pieced collectively one of the best components, then contracted a specialist film restoration firm to boost the degraded black-and-white movie and convert it into digital format for archival records.[5]

  • The SSTV system utilized in NASA‘s early Apollo missions transferred 10 frames per second with a decision of 320 body traces in an effort to use much less bandwidth than a standard TV transmission.[6]
  • The early SSTV programs utilized by NASA differ considerably from the SSTV programs presently in use by newbie radio lovers right now.


Industrial programs began showing in the US in 1970, after the FCC had legalized using SSTV for advanced level newbie radio operators in 1968.

SSTV initially required fairly a bit of specialised gear. Often there was a scanner or digicam, a modem to create and obtain the attribute audio howl, and a cathode-ray tube from a surplus radar set. The particular cathode-ray tube would have “lengthy persistence” phosphors that might hold an image seen for about ten seconds.

The modem would generate audio tones between 1,200 and a couple of,300 Hz from image alerts, and movie alerts from acquired audio tones. The audio can be hooked up to a radio receiver and transmitter.

Present programs[edit]

A contemporary system, having gained floor for the reason that early Nineteen Nineties, makes use of a personal computer and particular software rather than a lot of the customized gear. The sound card of a PC, with particular processing software program, acts as a modem. The computer screen supplies the output. A small digital camera or digital pictures present the enter.

A spectrogram of the start of an SSTV transmission


Calibration header


VIS code


RGB scanlines


Sync pulses


Like the same radiofax mode, SSTV is an analog signal. SSTV makes use of frequency modulation, during which each completely different worth of brightness within the picture will get a distinct audio frequency. In different phrases, the sign frequency shifts up or all the way down to designate brighter or darker pixels, respectively. Coloration is achieved by sending the brightness of every colour part (often purple, inexperienced and blue) individually. This sign will be fed into an SSB transmitter, which partly modulates the carrier signal.

There are a selection of various modes of transmission, however the most typical ones are Martin M1 (in style in Europe) and Scottie S1 (used principally within the USA).[7] Utilizing one in every of these, a picture switch takes 114 (M1) or 110 (S1) seconds. Some black and white modes take solely 8 seconds to switch a picture.


A calibration header is shipped earlier than the picture. It consists of a 300-millisecond chief tone at 1,900 Hz, a ten ms break at 1,200 Hz, one other 300-millisecond chief tone at 1,900 Hz, adopted by a digital VIS (vertical interval signaling) code, figuring out the transmission mode used. The VIS consists of bits of 30 milliseconds in size. The code begins with a begin bit at 1,200 Hz, adopted by 7 knowledge bits (LSB first; 1,100 Hz for 1, 1,300 Hz for 0). An excellent parity bit follows, then a cease bit at 1,200 Hz. For instance, the bits corresponding the decimal numbers 44 or 32 suggest that the mode is Martin M1, whereas the quantity 60 represents Scottie S1.


Sluggish-scan check card

A transmission consists of horizontal lines, scanned from left to proper. The colour elements are despatched individually one line after one other. The colour encoding and order of transmission can differ between modes. Most modes use an RGB color model; some modes are black-and-white, with just one channel being despatched; different modes use a YC colour mannequin, which consists of luminance (Y) and chrominance (R–Y and B–Y). The modulating frequency modifications between 1,500 and a couple of,300 Hz, comparable to the depth (brightness) of the colour part. The modulation is analog, so though the horizontal decision is commonly outlined as 256 or 320 pixels, they are often sampled utilizing any price. The picture aspect ratio is conventionally 4:3. Strains often finish in a 1,200 Hz horizontal synchronization pulse of 5 milliseconds (in any case colour elements of the road have been despatched); in some modes, the synchronization pulse lies in the midst of the road.


Beneath is a desk of a number of the commonest SSTV modes and their variations.[7] These modes share many properties, equivalent to synchronization and/or frequencies and gray/colour degree correspondence. Their fundamental distinction is the picture high quality, which is proportional to the time taken to switch the picture and within the case of the AVT modes, associated to synchronous knowledge transmission strategies and noise resistance conferred by means of interlace.

Household Developer Identify Coloration Time Strains
AVT Ben Blish-Williams, AA7AS / 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 – G3OQD M1 RGB 114 s 240¹
M2 RGB 58 s 240¹
Robotic Robotic SSTV 8 BW or 1 of R, G or B 8 s 120
12 YUV 12 s 128 luma, 32/32 chroma × 120
24 YUV 24 s 128 luma, 64/64 chroma × 120
32 BW or 1 of R, G or B 32 s 256 × 240
36 YUV 36 s 256 luma, 64/64 chroma × 240
72 YUV 72 s 256 luma, 128/128 chroma × 240
Scottie Eddie Murphy – GM3SBC S1 RGB 110 s 240¹
S2 RGB 71 s 240¹
DX RGB 269 s 320 x 256

¹ Martin and Scottie modes really ship 256 scanlines, however the first 16 are often grayscale.

The mode household known as AVT (for Amiga Video Transceiver) was initially designed by Ben Blish-Williams (N4EJI, then AA7AS) for a customized modem hooked up to an Amiga pc, which was ultimately marketed by AEA company.

The Scottie and Martin modes had been initially applied as ROM enhancements for the Robotic company SSTV unit. The precise line timings for the Martin M1 mode are given on this reference.[8]

The Robotic SSTV modes had been designed by Robotic company for their very own SSTV unit.

See Also

All 4 units of SSTV modes are actually out there in numerous PC-resident SSTV programs and not rely on the unique {hardware}.


AVT is an abbreviation of “Amiga Video Transceiver”, software program and {hardware} modem initially developed by “Black Belt Techniques” (USA) round 1990 for the Amiga house pc in style everywhere in the world earlier than the IBM PC household gained adequate audio high quality with the assistance of particular sound cards. These AVT modes differ radically from the opposite modes talked about above, in that they’re synchronous, that’s, they haven’t any per-line horizontal synchronization pulse however as a substitute use the usual VIS vertical sign to determine the mode, adopted by a frame-leading digital pulse practice which pre-aligns the body timing by counting first a method after which the opposite, permitting the heart beat practice to be locked in time at any single level out of 32 the place it may be resolved or demodulated efficiently, after which they ship the precise picture knowledge, in a totally synchronous and sometimes interlaced mode.

Interlace, no dependence upon sync, and interline reconstruction offers the AVT modes a greater noise resistance than any of the opposite SSTV modes. Full body pictures will be reconstructed with decreased decision even when as a lot as 1/2 of the acquired sign was misplaced in a stable block of interference or fade due to the interlace characteristic. As an example, first the odd traces are despatched, then the even traces. If a block of strange traces are misplaced, the even traces stay, and an affordable reconstruction of the odd traces will be created by a easy vertical interpolation, leading to a full body of traces the place the even traces are unaffected, the great odd traces are current, and the unhealthy odd traces have been changed with an interpolation. This can be a important visible enchancment over dropping a non-recoverable contiguous block of traces in a non-interlaced transmission mode. Interlace is an elective mode variation, nevertheless with out it, a lot of the noise resistance is sacrificed, though the synchronous character of the transmission ensures that intermittent sign loss doesn’t trigger lack of your complete picture.
The AVT modes are primarily utilized in Japan and the US. There’s a full set of them when it comes to black and white, colour, and scan line counts of 128 and 256. Coloration bars and greyscale bars could also be optionally overlaid high and/or backside, however the full body is on the market for picture knowledge except the operator chooses in any other case. For receiving programs the place timing was not aligned with the incoming picture’s timing, the AVT system offered for post-receive re-timing and alignment.

Different modes[edit]

Household Developer Identify Time [sec] Decision Coloration VIS VIS+P
PD[9] Paul Turner, G4IJE
Don Rotier, K0HEO-SK
PD50 50.000000 320 x 256 G, R-Y, B-Y
PD90 89.989120 320 x 256 99 99
PD120 126.103040 640 x 496 95 95
PD160 160.883200 512 x 400 98 226
PD180 187.051520 640 x 496 96 96
PD240 248.000000 640 x 496 97 225
PD290 289.000000 800 x 616


Utilizing a receiver able to demodulating single-sideband modulation, SSTV transmissions will be heard on the next frequencies:

Band Frequency Sideband
80 meters 3.845 MHz (3.73 in Europe) LSB
43 meters 6.925 MHz (Pirate Radio) USB
40 meters 7.171 MHz (7.165 in Europe) LSB
40 meters 7.180 MHz (New Urged Frequency to incorporate Basic Courses) LSB
40 meters 7.214 MHz Australian Digital SSTV frequency (Easypal and DIGTRX) LSB
20 meters 14.230 MHz Frequency 1 Analog. USB
20 meters 14.233 MHz Frequency 2 Analog to alleviate crowding on 14.230. USB
15 meters 21.340 MHz USB
10 meters 28.680 MHz USB
11 meters 27.700 MHz (Pirate Radio) USB
Encoded picture in B/W 8 system.
An SSTV image received by an amateur station transmitted from the ISS transmitted using the PD-120 mode.
An SSTV picture acquired by an newbie station transmitted from the ISS utilizing the PD-120 mode.
The ensuing image following decoding of the pattern SSTV transmission.
A Spectral Evaluation of the pattern SSTV transmission

In in style tradition[edit]

In Valve’s 2007 online game Portal, there was an web replace of this system information on 3 March 2010. This replace gave a problem to seek out hidden radios in every check chamber and produce them to sure spots to obtain hidden alerts. The hidden alerts grew to become a part of an ARG-style evaluation by followers of the sport hinting at a sequel of the sport – some sounds had been of Morse code strings that implied the restarting of a pc system, whereas others could possibly be decoded as purposefully low-quality SSTV pictures. When a few of these decoded pictures had been put collectively within the right order, it revealed a decodable MD5 hash for a bulletin-board system telephone quantity (425)822-5251. It supplies a number of ASCII art pictures regarding the sport and its potential sequel.[10][11][12] The sequel, Portal 2, was later confirmed. Based on a hidden commentary node SSTV picture from Portal 2, the BBS is working from a Linux-based pc and is linked to a 2400 bit/s modem from 1987. It is attached in an unspecified Valve developer’s kitchen. They stored spare modems in case one failed, and one did. The BBS solely sends about 20 megabytes of knowledge in whole.

Within the aforementioned sequel, Portal 2, there are 4 SSTV pictures. One is broadcast in a Rattman den. When decoded, this picture is a really refined trace in the direction of the sport’s ending. The picture is of a Weighted Companion Dice on the Moon. The opposite three pictures are decoded from a commentary node in one other Rattman den. These 3 pictures are slides with bullet factors on how the ARG was performed, and what the result was, equivalent to how lengthy it took the mixed web to unravel the puzzle (the common completion time was 7 1/2 hours).[13]

In one other online game, Kerbal Space Program, there’s a small hill within the southern hemisphere on the planet “Duna”, which transmits a colour SSTV picture in Robotic 24 format. It depicts 4 astronauts standing subsequent to what’s both the Lunar Lander from the Apollo missions, or an unfinished pyramid. Above them is the sport’s emblem and three circles.[14] It emits sound if an object is close to the hill.[citation needed]

Caparezza, an Italian songwriter, inserted a picture on the ghost track of his album Prisoner 709.

The Aphex Twin launch 2 Remixes by AFX incorporates a observe that shows an SSTV picture that has textual content in regards to the applications used to make the discharge in addition to an image of Richard sitting on a sofa.

See additionally[edit]



  1. ^ “Copthorne Macdonald’s Home Page”. January 2, 2014. Archived from the original on 2014-01-02.
  2. ^ Miller, Don. “SSTV history”. Retrieved Could 9, 2006.
  3. ^ Luna 3. Archived 2007-09-29 on the Wayback Machine.
  4. ^ a b Sven Grahn. “The Mercury-Atlas-9 slow-scan TV experiment”. Area Radio Notes.
  5. ^ Andrew Letten (2010-10-26). ‘Lost’ Apollo 11 Moonwalk tapes restored”. Cosmos Online. Archived from the original on July 20, 2014. Retrieved 4 November 2010. SYDNEY: After a three-year seek for the misplaced Apollo 11 tapes and an exhaustive six-year restoration mission, digitally remastered footage of the historic Moonwalk is sort of able to be broadcast.
  6. ^[bare URL PDF]
  7. ^ a b Langner, John. “SSTV Transmission Modes”. Archived from the original on February 16, 2003. Retrieved Could 8, 2006.
  8. ^ Cordesses, L. and R (F2DC) (2003). “Some Thoughts on “Real-Time” SSTV Processing.”. QEX. Retrieved September 2, 2008.
  9. ^ Turner, Paul. “The development of the PD modes”. Retrieved 2021-06-05.
  10. ^ Leahy, Brian (2010-03-01). “Portal Patch Adds Morse Code, Achievement – Portal 2 Speculation Begins”. Shacknews. Retrieved 2010-03-02.
  11. ^ Mastrapa, Gus (2010-03-02). “Geeky Clues Suggest Portal Sequel Is Coming”. Wired. Retrieved 2010-03-02.
  12. ^ Gaskill, Jake (2010-03-03). “Rumor: Valve To Make Portal 2 Announcement During GDC 2010”. X-Play. Archived from the original on 2018-01-08. Retrieved 2010-03-03.
  13. ^ Outcomes of 1 consumer decoding pictures with SSTV software program. Archived 2015-04-16 on the Wayback Machine. Retrieved 2012-08-14.
  14. ^ Decoding the KSP SSTV signal on YouTube

Exterior hyperlinks[edit]

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