Medium wave and HD radio do not do well together. Lightning discharge from lightning has been shown to knock out AM-HD signals well within their service area. Good luck getting severe weather warnings from an HD only AM station. Skywave can bring interference from distant stations. Strong skywave brings WBBM's HD sidebands with enough noise to interfere with my local 790 WTNY. The sideband method is inefficient and has made the whole AM band one noisy mess.
The fact that AM stations are switching to analog FM shows that AM has become a mess because of HD and less people are listening to it. Also the fact that HD isn't working because many of these HD AM stations have had an FM-HD simulcast for years yet feel the need to get their own analog FM signal. When scanning the AM band I've caught an ad from WCBS telling people to listen to 101.1 FM-3 to get WCBS 880 in HD. There was no mention of 880 having its own HD signal. Basically nobody listens to HD on AM.
The fact that AM stations are switching to analog FM shows that AM has become a mess because of HD and less people are listening to it. Also the fact that HD isn't working because many of these HD AM stations have had an FM-HD simulcast for years yet feel the need to get their own analog FM signal. When scanning the AM band I've caught an ad from WCBS telling people to listen to 101.1 FM-3 to get WCBS 880 in HD. There was no mention of 880 having its own HD signal. Basically nobody listens to HD on AM.