The timeline is wrong. We expected an FCC decision in 1977, when AM still had over half the listening. The FCC made a decision, which was immediately halted by Mr Kahn's lawsuit. It took 5 years to get to the "marketplace" decision, and then that was an effort by the FCC to prevent another suit by Mr Kahn.
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I don't want to sound argumentative with you, of all people, but my timeline is not wrong. It was 1980 when the FCC made the Magnavox decision. They had started "testing" about 1975. Technically there were 5 systems when the "marketplace" decision happened, but Belar dropped out almost immediately. I am unaware of any lawsuit by Mr. Kahn in the 70s, but know he filed one in the late 80s claiming Motorola's system did not meet FCC standards. If you recall, what was the lawsuit about in the 70s?
Also, the ease of making a multi-system chip does not count for the cost of licensing the technology from the 4 or 5 companies competing to be the standard. It was expensive. That's why only one such radio was made. (sure wish I had one)
10 or 15 years too late, the 1993 FCC decision was just too late for AM radio. I have studied AM Stereo for decades as part of my love of radio. I was acutely aware of every move made in the battles over it at the time it was happening. I have always wondered where the band would be today if it had managed to get a good stereo standard adopted back when most listeners were tuned in to AM. It amazes me that today only about 8-10% of listening in the DFW area is on the AM band. Would it be 20-30% if stereo had been adopted in the late 70s or early 80s? Probably not, but who knows.