Nu_Roo_2 said:
Interesting article. So the effective "near 100%" end of simulcasting in large/medium markets would have been at least a couple years later, after the mandated 50% split forced operators to pay attention to the band and listeners started catching on to its virtues. Of course many years down the road, AM began to slide and numerous faltering AMs started fully simulcasting their FMs.
In Dayton, Ohio...it actually begin in and around 1964, not so much with a simulcast split up, but with the addition of WDAO-FM...which was programmed from start up as what we today call an "Urban" format. And, interestingly enough, 'DAO in those days and in years later was big on playing "crossover" Top 40 music. (Back then, it was the Supremes, Temptations, James Brown, etc.).
In an interview I did a couple of years ago, WTUE Program Director Bill Struck (who was PD during most of the station's days as a "top 40" outlet), said he believed WDAO's presence on the FM band from 1964 on was actually drawing young listeners to the band years before it happened in other cities. And he credited WDAO with making it easier for WTUE to gain a foothold in younger listeners after they came on the air in the early 70's, because those listeners were already listening to FM.
If you read threads on this topic on boards from other cities here, you'll see where the posters say the audience change to FM happened there in the mid 70s...for some, even the late 70's. So, at the very least, whether by accident or design, Dayton was on the cutting edge of listeners moving from AM to FM...