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<nettime-ann> [ann] VSSTV - VERY SLOW SCAN TELEVISION
gebseng {AT} vinylvideo.com on Tue, 21 Mar 2006 20:03:39 +0100 (CET)


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<nettime-ann> [ann] VSSTV - VERY SLOW SCAN TELEVISION


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VSSTV - VERY SLOW SCAN TELEVISION

a new installation by Gebhard Sengm=FCller, in collaboration with Jakob 

Edlbacher (technical design), Johannes Obermayr (control 
engineering), Ludwig Ertl (programming), Gerhard Proksch-Weilguni 
(additional mechanics) and Andreas Konecky (additional programming)

Very Slow Scan Television (VSSTV) is a new television format that we 
have developed building upon Slow Scan Television (SSTV), an almost 
50-year-old image transmission system used by Ham Radio amateurs. In 
contrast to regular TV, SSTV runs on a dramatically reduced frame rate.

Developed in 1957 by Copthorne Macdonald, Slow Scan Television uses 
the shortwave radio band (Ham Radio) to transmit television images. 
Ham Radio not only broadcasts information (as is the case with 
conventional radio), but also uses the radio spectrum for personal 
communications, usually on a point-to-point basis over a previously 
negotiated frequency. In contrast to telephone conversations, this 
communication is open and can be listened to by anyone who happens to 

be tuned into the same frequency. The Ham Radio band was reserved for 

the purpose of voice transmission, and therefore uses only a small 
amount of bandwidth. Broadcasting images within this narrow bandwidth 

requires reducing their quality and rules out transmitting moving 
images. Furthermore, the visual information has to be converted into 
an audio signal.

According to British Ham Radio operator Guy Clark (N4BM), =93The 
original idea was to find a method of transmitting a television 
picture over a single speech channel. This meant that a typical (at 
that time) 3MHz wide television picture had to be reduced to around 
3kHz (1000:1 reduction). It was decided at the outset that the 
scanning rates must be very slow, which precludes the use of moving 
pictures. The choice of time base for synchronizing was the readily 
available domestic power supply at 50 or 60 Hz (depending on the 
country of origin). This gave a line speed of 16.6Hz and 120 or 128 
lines per frame (against the then UK standard of 405 lines (now 625) 
per frame), giving a new picture frame every 7.2 or 8 seconds. =85 The 

original SSTV systems were based on ex-government radar screens and 
cathode ray tubes with very long persistence (=93P7=94) phosphors. This 

allowed an image to be painted on the screen over a period of a few 
seconds.=94 The modulation technique often transmits defective images, 

evident in trapezoid distortions in the image caused by time 
synchronisation problems.=94

SSTV may suggest a parallel TV universe, one that developed during an 

era in which television monopolies were consolidating their hold over 

mass media culture. But it also shows similarities to current 
streaming and netcasting technologies where personal flair and taste 
determine the range of images broadcast.

Texts and pictures refer to the location of the sender and his or her 

identifier. Self-referential features dominate. Guy Clark writes: 
=93What kinds of pictures are sent? Reviewing pictures saved during the 

last few weeks I found: Hams in their shacks, lots of pet dogs, a 
frog, kangaroo, astronauts in the Space Shuttle (SSTV has been 
transmitted from some missions!!!), bridges, birds, Elvis Presley, 
rock formations, an old fashioned microphone, antique cars, flowers, 
children, Jupiter, a cow, someone playing bagpipes, a UFO, many 
colorful butterflies, boats, and cartoon characters with personalized 

messages. Even the Russian Space Station MIR has been transmitting 
SSTV pictures recently!=94

VSSTV uses broadcasts from this historic public domain television 
system =97available anytime over freely accessible frequencies=97and 
regular bubble wrap to construct an analogous system in which the 
packing material functions as the aperture mask. Just as a Cathode 
Ray Tube mixes the three primary colors to create various hues, V
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