Narrow-bandwidth television

Narrow-bandwidth television (NBTV) 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 (though channels ranging into a few tens of kilohertz and beyond can also be used). This is in contrast to regular TV systems that use a channel about six to eight megahertz wide.

Design

There are two ways to make this work: reduce the scan rate, or reduce the image size. When the scan rate is reduced, this is referred to as slow-scan TV. With the latter type, the number of lines in an image may be reduced to just a few dozen.

The earliest mechanical television systems often used narrow channels for sending moving images. Often, the images were only a few dozen lines in size. However, most narrow-bandwidth TV nowadays uses computers and other electronic systems.

Mechanical TV standards

Name	Details
Nipkow 1884	24 lines. Patent granted but Nipkow did not build a system.
WGY, 2XAF, 2XAD	24 lines, 21 frame/s, progressive scan
England 1926 (Baird)	30 lines, 5 frame/s, black-and-white experimental transmissions
England 1928 (Baird)	30 lines, 5 frame/s, first experimental colour TV transmissions
2XAL New York 1928	48 lines, 7.5 frame/s, progressive scan
Baird, England, 1928-32	30 lines, 12.5 frame/s, 3:7 vertical aspect ratio, vertical progressive scan, ~70x30 pixels per frame, sound, live TV from studio
W9XAA/WCFL, W9XAO/WIBO, W9XAP/WMAQ (Western Television / Sanabria), Chicago, 1928-33	45 lines, 15 frame/s, 1:1 aspect ratio, triple interlace scan. Live TV from studio. (Above transmissions: Picture station / sound station)[1]
W9XK/WSUI, Iowa City, Iowa (Used Western Television / Sanabria system), 1933-39	45 lines, 15 frame/s, 1:1 aspect ratio, triple interlace scan. Includes sound on WSUI. Educational TV pioneer. Live TV from studio. [1]
Germany, France, 1930	30 lines, 12.5 frame/s, 3:4 aspect ratio, horizontal progressive scan
New York City, Schenectady, Boston, 1930-31	48 lines, 15 frame/s, 6:5 aspect ratio, horizontal progressive scan
W6XS Los Angeles, 1931	80 lines, 20 frame/s, progressive scan
W6XAH Bakersfield, 1931	96 lines, 20 frame/s, progressive scan
New York, Schenectady, Boston, 1932	60 lines, 20 frame/s, 6:5 aspect ratio, horizontal progressive scan
Berlin 1932	30 lines, 12.5 frame/s, 4:3 horizontal aspect ratio, ~40x30 pixels per frame, test movies and live images
Königswusterhausen 1932	39 lines, 12.5 frame/s, 4:3 horizontal aspect ratio, ~31x30 pixels per frame, movies
Doberitz 1932	48 lines, 25 frame/s, 4:3 horizontal aspect ratio, ~64x48 pixels per frame, sound, talking movies
Berlin R.P.Z. 1932	60 lines, 25 frame/s, 4:3 horizontal aspect ratio, ~83x60 pixels per frame, test movies and live images
Italy 1932	60 lines, 20 frame/s, 4:3 horizontal aspect ratio, ~45x60 pixels per frame, test movies and live images
France 1932	60 lines, 12.5 frame/s, 3:7 vertical aspect ratio, vertical scanning ~35x60 pixels per frame, sound, live images
Switzerland 1932	30 lines, 16.6 frame/s, 4:3 horizontal aspect ratio, ~40x30 pixels per frame, test movies and live images
USSR 1932	30 lines, 12 frame/s
Belgium 1932	30 lines, 12.5 & 16.6 frame/s, 4:3 horizontal aspect ratio, ~40x30 pixels per frame, sound, talking movies

References

1. ^ ^{a b} "Early Chicago Television, Mechanical Tv, Ua Sanabria". Hawestv.com. http://www.hawestv.com/mtv_chicago/mtv_cgo.htm. Retrieved 2010-03-02. 

External links

• W9XK Experimental Television at the University of Iowa
• The Narrow Bandwidth Television Association