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For example, I like the idea of low power AM to complement LPFM, to serve local areas…
One thing I forgot to mention, and was reminded of this while watching a somewhat unrelated video (Analog vs Digital on the techquickie youtube channel) in which AM radio was mentioned in passing.
My reason for choosing AM, as opposed to FM, primarily has to do with simplicity of the technology.
Also I've had another idea too, which is a bit more involved, involving reshuffling the band.
Expand the FM band to 76 MHz (like I've heard proposals to do.) Move as many AMs to FM as possible, with a transition period just long enough to make sure the equipment works. Coverage of the FM should be preferably greater than the former AM, not including skywave or low-frequency high-conductivity high-AM-power groundwave, primarily emphasizing the good-signal zone, not including DX.
Restructure AM so that the lower frequencies are used for wide-area coverage, the middle frequencies are for regional stations, and the highs are for local stations. Also, digital would get its own set of frequencies - you wouldn't, for example, have 1280 kHz in digital in Long Beach, CA, and in analog in New York, NY.
On the low frequencies, each network (be it ESPN, Premiere, Westwood One, whoever syndicates Rush & Hannity, Salem, Family Radio, Air 1, K-Love, Radio Disney, etc.) would get their own dedicated frequency, and build their own networks of high-power high-efficiency transmitters to blanket the 48 states. (High power meaning 1 megawatt or more, high efficiency meaning 510 mV/m/km/kW or more.) Channel spacing would be wider, like 30 kHz, with audio out to 15 kHz, to eliminate first-adjacent overlaps. (You could stand next to a 570 transmitter site and hear 600 without any interference or desense in full quality.) These transmitters would be synchronized, and the only deviation from simulcasting would be the TOH callsign ID. All ads would be of a national nature. (Of course going locally-oriented would be okay for emergencies.) However, if we could get
wireless data service on smartphones, laptops, etc. to where you can get it anywhere in the country that it'd be possible to detect an AM signal, including remote wilderness areas, and also inside buildings that AM doesn't penetrate due to structure or RFI,
without the customer having to pay a monthly service fee, just buy the radio, or have already bought the wifi-capable phone or laptop ... then my high-power AM nationwide network coverage idea wouldn't be necessary. But, the wireless service would need to cover every square inch of the 48 states with a solid signal, and cannot have recurring costs to the consumer, other than repairing failing or replacing aging equipment.
For the medium frequencies, they'd all be independently owned and operated, serving various regional areas, from as small as a single medium-large metro area like Washington, DC, to as large as a few states like the four corners states.
Last, but not least, and this was the category I was thinking about with LPAM & similar ... the high frequencies would be for the low power stations, like LPAMs and possibly the graveyards. (Although I'd expect all of those would get moved to FM.) Using high frequencies, I think, would be because you don't need as tall of an antenna to be efficient, and the signals die off faster over distance. Once you got outside the local coverage area, it wouldn't be as far to go before your signal dies out. Also, being AM (and no HD/IBOC to be used), it would be simple technology, and in many cases especially LPAM, station owners could all but build their own transmitter & antenna just by scrapping electronics from no-longer-needed appliances or gadgets, or even make their own capacitors, resistors, diodes, etc, where necessary, if they're skilled enough. Also receivers would be simple to make, just like normal AM radios.

(Of course DSP can offer better performance, but at least a simple diode, coil, variable capacitor, amplifier, earphone, etc. would work. (Even a typical 1st grader would be able to get a low powered station on to cover the geographical area in which his or her classmates live.) Also, the low-power stations, as much as possible, would not need to have their antennas fenced.