The third adjacent channel protection removal has been proposed but NOT enacted. By the late 1950s, most AM stations no longer had reliable reception beyond their protected contours. In the old days, a 250 watt AM station in South Georgia could be heard out 75 miles or so. There were no stations on the air and radio receivers were very sensitive. As more stations came on the air, following the FCC rules, reliable reception dropped to the protected contour.
We still have lots of FM stations enjoyed strong reception beyond their protected 60 dBu contours. Any new stations coming on the air, full power or translators must still protect the 60 dBu. You're right that reception is reduced beyond that contour strength but if you want to protect that far distant signal, you would have to get the FCC to greatly tighten signal protection and that is not going to happen.
Also, keep in mind that FM receivers today are much more sensitive than they were even in the 1970s. FM receivers have improved, AM receivers have declined.
A 1930s tube AM receiver picks up a lot better than an AM radio in a high end car will today in 2010 and that's without an outside long wire antenna on the 1930s radio.
The demise of many AM radio stations had something to do with programming but the dulling down of AM radio receivers and no longer requiring electric utility companies to "sniff" power lines for electrical AM radio inteference played as big or a bigger role and ultimately the blame must be placed on AM radio station operators of that day who didn't use their political influence to protect their franchise...especially in rural areas. All that being said, FM sounds better and most instances is cheaper and less complicated to operate.
My experience has been that by the time the FCC gets around to resolving a problem, it's way too late to make much of a difference.
FM translators are making a huge positive difference for smalll market AM radio stations.
secondchoice said:
The Commission has removed some of the protection (IIRC the third adjacent) for the C’s under the guise of creating a bunch of “community” low power stations. IMHO these should go to class D AMs.
A better answer is to take channel 5 and 6 analog TV channels for “an all digital band”. These stations would be max 50KW at 500 ft (similar to the B’s in the northeast). Being all digital there would be very little adjacent channel issues and good building penetration. I would require a (shareware or free) digital scheme that has not noticeable time delay. The C and D AM’s can simulcast for 5 years then the AM band is cleaned up for high power AM stations with HD. Also there has to be a reduction to 3 or 4 signals (AM and FM) per market limit per owner. If you can not make money with 4 signals in a market then you need to sell out to someone who can!