Editing AM broadcasting (section)

===HD radio===
{{Main|HD Radio}}
[[File:Hdradio-logo.svg|right|200px|thumb|alt=]]

HD Radio is a digital audio broadcasting method developed by [[iBiquity]]. In 2002 its "hybrid mode", which simultaneously transmits a standard analog signal as well as a digital one, was approved by the FCC for use by AM stations, initially only during daytime hours, due to concerns that during the night its wider bandwidth would cause unacceptable interference to stations on adjacent frequencies.<ref>{{cite news |first=TaNoah |last=Morgan |date=11 October 2002 |title=Digital radio approved by FCC |newspaper=[[Baltimore Sun]] |url=https://www.baltimoresun.com/news/bs-xpm-2002-10-11-0210110010-story.html}}</ref> In 2007 nighttime operation was also authorized.<ref>{{cite news |first=Peter |last=Gutmann |date=23 August 2007 |title=HD Radio rules take effect |website=Radio+Television Business Report (RBR.com) |url=https://www.rbr.com/hd-radio-rules-take-effect-by-peter-gutmann/}}</ref>

The number of hybrid mode AM stations is not exactly known, because the FCC does not keep track of the stations employing the system, and some authorized stations have later turned it off. But as of 2020 the commission estimated that fewer than 250&nbsp;AM stations were transmitting hybrid mode signals.<ref>{{cite news |title=Proposed rule: All-digital AM broadcasting, revitalization of the AM radio service |date=25 November 2019 |periodical=[[The Federal Register]] |url=https://www.federalregister.gov/documents/2020/01/07/2019-27609/all-digital-am-broadcasting-revitalization-of-the-am-radio-service}}</ref> On October 27, 2020, the FCC voted to allow AM stations to eliminate their analog transmissions and convert to all-digital operation, with the requirement that stations making the change had to continue to make programming available over "at least one free over-the-air digital programming stream that is comparable to or better in audio quality than a standard analog broadcast".<ref>{{cite news |title=Final rule: All-digital AM broadcasting, revitalization of the AM radio service |date=3 December 2020 |periodical=[[The Federal Register]] |url=https://www.federalregister.gov/documents/2020/12/03/2020-25252/all-digital-am-broadcasting-revitalization-of-the-am-radio-service}}</ref>