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Thursday, December 10, 2015

Channel 1

RCA 630-TS, the first mass-produced television set, 1946–1947
Detroit Steve sent me a link to a story by J. W. Reiser on Tech-Notes dot tv about why our television sets start with channel 2 instead of channel 1. Television got started back in 30's. A lot of people were very excited about it, but the manufacturers needed a standard for the signals so TV sets could receive signals being transmitted by commercial broadcasters. As you might expect there was a bunch of pushing and shoving involved, and then WW2 came along and disrupted things six ways from Sunday. Anyway it's good story. Here's an excerpt about the early history:
During the first few months of 1933, the Radio Corporation of America (RCA) demonstrated the first successful all-electronic television system.  Broadcasts were made from the RCA experimental television transmitter, W2XBS, located at the top of the Empire State Building in New York City.  The characteristics of that early all-electronic television system were modest:
Lines:
Frames:
Scanning:
Bandwidth:
Video carrier:
Audio carrier:
240
24 per second
Sequential (no interlacing)
2 MHz
AM modulated, full sideband
AM modulated, full sideband
Yet, the results were far better than any mechanical television system had ever accomplished.  For those experiments, the video carrier was approximately 45 MHz.

It may be hard for us to appreciate fully what RCA had accomplished in 1933.  But to give you an idea: Many of the experimental television broadcasts were still using frequencies in the 2 to 3 MHz range, and bandwidths of 100 kHz.  In addition, the earlier systems were mechanical using gears, motors, mirrors, etc.  As television advanced, each step pointed towards non-mechanical systems, and higher bandwidths and carrier frequencies.

The Federal Communications Commission (FCC) was established by an act of Congress on June 22, 1934.  It was about that time that a portion of the VHF radio spectrum was allocated to television for the first time (see Table 1).
Table 1
The colors are just so you can see how various frequencies got moved around. 

You can see from the table that there used to be a Channel 1, but since was a 'community' channel, it got squoze out by the big boys.


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