Mechanical TV Standards

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Mechanical Television

Mechanical TV Standards

The following is from James Hawes:

For the public, the US mechanical TV boom really started in 1928. The stations of the time had at best local standards and at worst no standards. A popular cartoon shows a TV viewer sitting in a chair on casters. To "change channels," he slides the chair down a row of scanners, each with its own TV standard! Sort of an in-joke, but it paints the true picture.

In October 1928, the RMA discussed the problem and recommended two regional standards, 60 and 48 lines. The 60-line format came from Frank Conrad at Westinghouse. RCA adopted 60 lines and abandoned 48 lines, the standard of Ernst Alexanderson at General Electric. After RCA began transmitting with 60 lines, most stations on the Eastern Seaboard followed suit. Of course, 60-line transmissions were too broad for standard medium-wave (AM band) channels. Responding to the situation in 1929, the FRC moved television to the 160-meter shortwave band. Channels in this band were broad enough for pictures of up to 70 lines at 20 fps. (Or more conservatively, 60 lines with ample guard bands. I assume square pixels.) See Abramson, The History of Television, 1880-1941, p. 128. Also Udelson, The Great Television Race, pp. 45-46.

In the late 1920s and early 30s, several mechanical TV transmission standards were being used. Here are the details on most of them:

Lines	Frames/ Second	Aspect Ratio (H:V)	Scan	Direction (r=right, l=left, t=top, b=bottom)	Sync	Notes
24	21	?	Progressive	l-r, t-b	?	WGY, 2XAF, 2XAD
30	12.5	3:7	Progressive	r-l, b-t	Phonic	Baird, England, 1928-32
30	12.5	1:1	Progressive	l-r, t-b	Phonic	Germany, France, 1930
36	?	?	Progressive	l-r, t-b	?	W2XAL, WRNY New York 1928
45	15	1:1	Triple interlace	r-l, t-b	Synchronous	W9XAL, WCFL, W9XK midwest, 1929-32
48	7.5	?	Progressive	?	?	2XAL New York 1928
48	10	?	Progressive	?	?	WRNY New York 1928
48	15	6:5	Progressive	l-r, t-b	Synchronous	East coast, 1930-31
48	20	?	Progressive	?	Synchronous	WGY (G.E.)
60	20	6:5	Progressive	l-r, t-b	Synchronous	East coast, 1930-32
80	15	?	Progressive	?	Synchronous, blacker than black sync pulse	W6XS Los Angeles, 1931-36
96	20	?	Progressive	?	?	W6XAH Bakersfield, 1931

Early Television