The problem with AM is the audio fidelity. Yes, interference from natural and manmade causes
is an issue as well as interference from other broadcasters. But even if you fixed that, AM just doesn't sound very good. 10kHz of bandwidth was fine when the standards were set in the 20s or 30s. That's about all a 78rpm record could do. Until the audio sounds better, AM isn't going to improve. Even many talk stations are moving to FM now. So how can AM be improved?
If AM stations were able to use their 10kHz for 10kHz worth of audio, it would sound much better. Currently, the upper and lower sideband are each 5kHz but contain the same information. If only 1 sideband was used then the frequency range could be extended. It wouldn't quite be FM, but it would be enough to do justice to most popular music. The static would still be there but it would be better than the IBOC nonsense that currently interferes in most places.
They could do away with the carrier but that would make receivers more complex and leave it
non-compatible with existing radios. An older radio tuning into a new "hi-fi" AM stations would probably exhibit a lot of ringing due to the narrow filters. But they would still sound good on the talk stations that wouldn't need hi-fi right away. A receiver equipped with the wider filters would sound good. I suppose it might be necessary to center the sideband where the carrier now sits so as not to interfere with stations not making the transition. A station on 650khz would put it's carrier at 645khz with the sideband occupying from 645 to 655. The downside is that current receivers often won't tune 645khz.
There would be many challenges to changing over to something like this. It might even be better to just go completely digital; possibly with a narrow band FM carrier. There were some hi-fi AM stations at one time that occupied 20kHz channels from 1500-1600. I'm not sure why they were scrapped. Maybe it didn't work very well. I could see there might be phase problems on a signal that wide on those frequencies. AM is turning into a place to warehouse a format so that it can be simulcast on an FM translator. Many are now simulcast on FM HD2 channels. It's losing it's place as many talk stations are now moving to FM; taking the one format that still worked on AM. It would be nice to make AM viable again in it's own right as an analog format. It may make noise when lightning flashes, but at least it doesn't cut for 2 seconds like digital does.
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