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 AMATEUR TELEVISION 

From Wikipedia, the free encyclopedia

Amateur Television (ATV) is the hobby of transmitting broadcast-quality video and audio over radio waves allocated for amateur radio using the broadcast standards of NTSC in North America and Japan, and PAL or SECAM in Europe and elsewhere, using the full refresh rates of those standards. ATV includes the study of building of such transmitters and receivers and the propagation between these two.

 

ATV is an extension of amateur radio. It is also called HAM TV or Fast Scan TV (FSTV). Ham operators are also allowed to transmit Slow Scan TV (SSTV) which is similar to video facsimile. SSTV may be transmitted within the voice segments of all ham radio frequency bands, though it is used primarily below 28 MHz.

 

North American context

 

In North America, transmissions are typically sent from repeaters on four UHFchannels below the UHF TV broadcast band (air channels 14 to 69) (between channels 13 and 14, in the 70 cm ham band). These can be received on a cable-ready NTSC-format TV or set-top box tuned to cable channels 57 to 60 (420-444 MHz).

 

Individual channels (with center frequency for video and audio) are:

  • 57: 420-426 MHz (421.25 video, 425.75 audio)
  • 58: 426-432 MHz (427.25 video, 431.75 audio)
  • 59: 432-438 MHz (433.25 video, 437.75 audio) - offset to 434.0 and 438.5 to clear the satellite sub-band

                     (435-438).

  • 60: 438-444 MHz (439.25 video, 443.75 audio)

 

All of these fall within the range between T.V. broadcast channels 13 and 14, which are:

  • 13: 211-216 MHz (211.25 video, 215.75 audio)
  • 14: 471-476 MHz (471.25 video, 475.75 audio)

 

The other microwave amateur radio bands also have ATV usage with vestigal side band (North American analog TV broadcast modulation standard) on 919.25 MHz, 1241.25 MHz, 1253.25, MHz, 1277.25 MHz and 1289.25 MHz usually for cross band ATV repeater outputs. 1265 MHz is a wider channel (10 MHz) for AM or FM ATV. Some areas in North America use 1255 MHz FM.

 

Most of the FM ATV is on 2441.5 MHz with 6.0 MHz audio subcarrier and 4 MHz deviation. ATV links are on 2417.5 MHz, 3GHz and 5 GHz bands have links in some areas. 10.4 GHz is a wideband FM and used in some ATV repeater inputs. The distance record for ATV is between Hawaii and California on 434 MHz.

 

Experiments with digital modes have lagged somewhat behind those in Europe, but have taken on some new urgency given the transition of broadcast television.WR8ATV currently has an output using DVB-S, which is believed to be the first, and currently only, D-ATV repeater in the US.

European context

In Europe, which generally has a narrower UHF allocation than the USA, the majority of amateur television operation is currently FM on 1.2GHz and above. The frequencies in use depend on national permissions. In most of mainland Europe, the most common frequency is 1255MHz. Other bands commonly used for ATV are the 13cm (~2.3-2.45GHz) and 3cm (~10GHz) bands, although ATV is used on most of the microwave bands.

 

In several countries cross-band repeaters are used, with AM inputs on 430 MHz and FM outputs on 1255 MHz, others have FM-ATV inputs on 13 cm and outputs on 3 cm.

 

In the United Kingdom, much activity occurs using in-bandrepeaters. These generally have an input of 1248, 1249 or 1255MHz and typically output at 1308, 1312 or 1316 MHz, although other frequencies are also used. Simplex operation occurs on these or other frequencies chosen to avoid interference with other users of the band, e.g. 1285MHz. Recent experiments have been done with digital modes following widely-adopted DVB-S and DVB-T standards.

Transmission standards

Typically frequency modulatedTV is used on frequencies above 1200 MHz (1.2 GHz), where there is enough bandwidth for such widebandtransmissions. This is often used as a repeater's input frequency, with output being standard VSB on the four channels listed above.

In a nutshell

 

 

SCREEN SHOT OF AN AMATEUR TELEVISION TRANSMISSION

 

 

INFORMATION FROM

ON FAST SCAN TV

 

CLICK ON >>>ATV PART 1 PDF<<< CLICK ON

 

CLICK ON >>>ATV PART 2 PDF<<< CLICK ON

 

CLICK ON >>>ATV PART 3 PDF<<< CLICK ON

 

 

 

FAST SCAN ATV GROUPS

 

 

Welcome to the Amateur Television Directory, the internets first stop for finding sites related to Amateur Television and Ham Radio. Find out where Amateur Television is being used in your state or country.

You can also find out where to buy transmitters, receivers, antennas, cameras, and all the other things you will want (need) to get your Amateur Television station on the air.

 

CLICK ON >>>ATV-TV WEB SITE<<< CLICK ON

 

 

Welcome to the Home Page of
The Amateur Television Network

Fast Scan Amateur Television in Alabama, Arizona, Northern California
Southern California, Georga, Illinois, Indiana, Kentucky, New Mexico, Nevada,
Texas, Washington, Delaware, Maryland, New Jersey, and Pennsylvania.
( . . . and worldwide by way of the internet.)


Welcome internet ATV viewers!


Enjoy yourself as you explore our web site.

If you are interested in developing a chapter of ATN for your area you can contact Don Hill at hillda@cox.net
or Mike Collis at wa6svt@aol.com

Thank you for visiting the ATN web site.
 
CLICK ON >>>ATN WEB SITE<<< CLICK ON
 

 

SLOW-SCAN AMATEUR TELEVISION

From Wikipedia, the free encyclopedia

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

 

A technical term for SSTV is narrowband television. Broadcast television requires 6 MHz wide channels in North America, because it transmits 25 or 30 pictures per second (in the NTSC, PAL or SECAM systems), but SSTV usually takes up to only 3 kHz of bandwidth. It is a much slower method of still picture transmission, usually lasting from about eight seconds to a couple of minutes.

 

Since SSTV systems operate on voice frequencies, amateurs use it on shortwave (also known as HF by amateur radio operators), VHF and UHF radio.

 

 

SLOW-SCAN TRANSMISSION WITH "RST" REPORT AND CALL SIGN

 

Concept

 

The concept of SSTV was introduced by Copthorn 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

 

SSTV was used to transmit images of the far side of the Moon from Luna 3.

 

The first space television system was called Seliger-Tral-D and was used aboard Vostok. Vostok was based on an earlier videophone project, it used two cameras, with persistent LI-23 iconoscope 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 Vostok capsule, including Sputnik 5, containing the space dogs Belka and Strelka, whose images are often mistaken for the dog Laika and the 1961 flight of Yuri Gagarin, the first man in space on Vostok 1.
  • Vostok 2 and thereafter used an improved 400-line television system referred to as Topaz.
  • A second generation system (Krechet, incorporating docking views, overlay of docking data, etc) was introduced after 1975.

 

A similar concept, also named SSTV, was used on Faith 7 as well as on the early years of the NASAApollo program. The Faith 7 camera transmitted one frame every two seconds.

 

SSTV was used to transmit images from inside Apollo 7, Apollo 8, and Apollo 9, as well as the Apollo 11Lunar Module television from the Moon, see Apollo TV camera.

 

  • The SSTV system used in NASA'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 FCC had legalized the use of SSTV for advanced level 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 from a surplus radar set. The special cathode ray tube would have "long persistence" phosphors that would keep a picture visible for about ten seconds.

 

The modem 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 and transmitter.

Current systems

A modern system, having gained ground since the early 1990s, uses a personal computer and special software in place of much of the custom equipment. The sound card of a PC, with special processing software, acts as a modem. The computer screen provides the output. A small digital camera or digital photos provide the input.

Modulation

SSTV uses analogue frequency modulation, in which every different value of brightness 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 transmitter, which in part modulates the carrier wave.

 

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.

VIS code

A digitalVIS (vertical interval signaling) code can be sent before the image, identifying the transmission mode used. It consists of bits of 30 milliseconds in length. The code starts with a start bit at 1200 Hz, followed by 7 data bits (LSB first; 1100 Hz for 1, 1300 Hz for 0). An even parity bit 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 RGB color components are sent separately one line after another in the order R, G, B. Some Robot modes use a YC color model, which consists of luminance (Y) and chrominance (R-Y and B-Y). The modulating frequency changes between 1500 and 2300 Hz, corresponding to the intensity (brightness) of the color component. The modulation is analogue, so there is not a defined number of pixels in each line; they can be sampled using any rate (though in practice, the image aspect ratio is conventionally 4:3). Lines end in a 1200 Hz horizontal synchronization pulse of 5 milliseconds (after all color components of the line have been sent).

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.

 

FamilyDeveloperNameColorTimeLines
AVTBen Blish / AEA8BW or 1 of R, G, or B8 s128×128
16wBW or 1 of R, G, or B16 s256×128
16hBW or 1 of R, G, or B16 s128×256
32BW or 1 of R, G, or B32 s256×256
24RGB24 s128×128
48wRGB48 s256×128
48hRGB48 s128×256
104RGB96 s256×256
MartinMartin EmmersonM1RGB114 s240¹
M2RGB58 s240¹
RobotRobot SSTV8BW or 1 of R, G or B8 s120
12YC12 s128 luma, 32/32 chroma × 120
24YC24 s128 luma, 64/64 chroma × 120
32BW or 1 of R, G or B32 s256 × 240
36YC36 s256 luma, 64/64 chroma × 240
72YC72 s256 luma, 128/128 chroma × 240
ScottieEddie MurphyS1RGB110 s240¹
S2RGB71 s240¹

¹ Martin and Scottie modes actually send 256 scanlines, but the first 16 are usually grayscale.

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 Amiga home computer popular all over the world before the IBM PC family gained sufficient audio quality with the help of special sound cards. 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 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 modulation, SSTV transmissions can be heard on the following frequencies:

 

BandFrequencySideband
80 meters3845 kHz (3730 in Europe)LSB
40 meters7170 kHz (7043 in Europe)LSB
20 meters14,230 kHzUSB
15 meters21,340 kHzUSB
10 meters28,680 kHzUSB

 

 

Amateur Radio Slow Scan TV

by Rob Aarssen (VE3RDN)

 

SSTV Brief Explanation!
The best way to understand slow scan TV is to imagine it as colour fax pictures but sent over the radio rather than the phone. The pictures are transmitted via tones (1200-2300 HRZ) over the air. There are several simple ways to get setup for slow scan TV, the simplest of which use your computer and software with a hardware interface. There are interface circuits which work excellent and cost less than $20 to build or nil if from your junk box.
 
My experience with slow scan has been great fun. I've exchanged picture QSLs with different people in many different countries throughout the world. The quality of the pictures is somewhat dependent upon the computer, (monitor & graphics card), and somewhat on the software, hardware. The better systems support Hicolour which gives typical picture resolutions of 320 x 240 in 32 thousand colours. These pictures are almost photographic quality and are very impressive to say the least.
 
Once you've tried it your hooked. Imagine being able to swap mug shots with other Amateurs. See who you're talking to. Send diagrams and schematics over the air. It's great. Listen to HF on 14.230 and 14.233 almost anytime to hear the action. Don't be afraid to break in for info. The SSTV hams are usually very willing to help other interested parties or help you get started in slow scan. Go for it and I'll see you on the air.

 

CLICK ON >>>VE3RDN SSTV WEB SITE<<< CLICK ON

 

 

SSTV TRANSMISSION EXAMPLES

 

    

 

    

 

    

 

SOME SEXY SSTV TRANSMISSION EXAMPLES

 

 

 

 

 

 

INFORMATION FROM

ON SSTV

 

 

CLICK ON >>>GETTING STARTED WITH SSTV PDF <<< CLICK ON

 

CLICK ON >>> SSTV IS NOT EXPENSIVE ANY MORE PDF <<< CLICK ON

 

 

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