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The 15.734 pilot was chosen not so much over bandwidth issues, but the fact that NTSC color TV uses 15.734 (and some pocket change) as the video line frequency.
This line frequency gets all over a typical TV set in many ways. The video signal itself consists of concentrations of RF every 15.734¢¢ kHz, many older sets actually use B+ boost (from the horizontal sweep circuit and full of 15.734¢¢ and its harmonics) to power a gated quadrature detector tube, and the horizontal sweep circuit sends 15.734¢¢ to other circuits by happenstance (through the power supply and/or magnetic field induction). Thus, a 19kHz pilot would have caused an annoying 3,266 Hz howl in a whole bunch of TV sets. L-R subcarrier sidebands at multiples of 19kHz could have caused problems with the NTSC color subcarrier as well. Using 15.734¢¢, the harmonics are "interleaved" with the chroma, just as the luminance is.
I think the real barrier to stereo TV was that the broadcasters may not have wanted it. From the broadcasters' perspective, stereo TV would have meant adding stereo exciters at many points in the broadcast chain, replacing perfectly good monaural audio boards with stereo ones, and having to set up microphones in two or more places in every studio set. Going stereo may have helped one station get an edge over the rest, but this would only result in every other studio/network/station going stereo, too. A big investment for a net audience gain of zero.
This same school of thought affected the adoption of FM, and is what really killed AM stereo (demonstrated in 1960, but kept off the market until 1983, by which time it was too late).
Last edited by Robert Grant; 02-18-2010 at 09:59 PM.
Reason: fix mathematical error
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