Why did Stereo TV broadcast take so long to appear?
 

Seeing as modern FM stereo was established in the early sixties, why did it take so long to reach TV? Aren't they pretty much the same? Or was there lack of a commercial interest, or FCC regulations, like with the AM band?

I'll have a try..

Multiple interests worked on a stereo TV scheme for about 10 years before the Zenith system was finally approved by the FCC in 1984. At least they settled on one. They let AM stereo's 4 systems battle it out, and nobody won. Same thing with quadraphonic in the '70s.. died off from 4 competing systems confusing things, and everyone gave up for the time being, until surround sound resurrected it.

It was easier to do in Europe where they had 8mHz channels - all that spare bandwidth to play with. I think German scheme achieved better analog stereo (closer to FM broadcast quality) than US Zenith system which was a bit complicated with its use of DBX compression/expansion etc. for second channel

That complexity is why there were few if any stereo RF modulators in VCRs etc. only one TOTL Panasonic VCR, and two C-band satellite receivers I know of, had stereo RF out. I used a "Stereo 2000" modulator to send stereo from my satellite receiver on ch 3 to other sets in the house.

I'm just looking at pages 724-725 of the book 'Introduction to Communication
Systems, 3rd edition.', by Stremler, which presents a brief description of the
stereo system used from 1984 to the end of analog TV with the NTSC
standard. The pilot was at 15.734 kHz (instead of 19 kHz for FM radio),
in order to accomodate the tighter bandwidth available. I guess receiver
hardware to accomodate a pilot frequency so close to the upper limit
of the audio frequency range (nominally 15 kHz) was too hard to design for
mass production until the eighties. By the way, this pilot frequency was
chosen to be equal to the horizontal sweep frequency, another trick
worked out by those funny analog engineers. Let their technical abilities
not get forgotten in this so-called digital world...

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).

Interesting comments Robert, but I still think standard stereo FM with 19 kHz
pilot would be too wide for NTSC TV. Also, the TV standard as defined allows
for some extra audio channels, somewhat different from the SCA scheme.

Regarding the need for extra mikes, that certainly makes sense, but I do know
a number of radio stations that don't bother with extra mikes: the music is
in stereo but as soon as the announcer gets on the air, it is obvious that
the studio has a single mike!

By the way, we still have NTSC TV here in Canada (officially until Aug. 31, 2011),
and all the stations I know do send the stereo pilot. Is their audio actually in
stereo? I would not say I care much, especially when watching an older single
speaker TV set! Regards.

Actually, we still have NTSC in the states, as well:

Most low power (LPTV) stations are still analog.

All VCRs and most DVD players and video games output in NTSC.

Those converter boxes convert ATSC digital programs to NTSC, so, many people watching digital stations are still actually watching NTSC.

Those of us near the Mexican or Canadian borders can still get Mexican or Canadian stations in analog OTA. CBET (Windsor's CBC station) is watched frequently here (it is kinda sad to note that CTV, not CBC, has the Winter Olympic franchise this year, as CBC always had good Olympic coverage to supplement the US networks).

The biggie: Analog cable. Despite Comcast's "Project Cavalry" project, millions of Americans on other cable systems are watching NTSC just as they did before last June.

I seem to remember when I had analog cable TV, and this was probably 10 years ago, that none of the channels were in stereo except maybe MTV...even though the over-the-air channels' broadcast (or the original cable channels satellite feed) was in stereo, the cable company transmitted it in mono.