It seems there's a gap in the format list on Medium for radio broadcast's. It sounds like the guidelines here say to use "Digital Media", but whilst most modern broadcasts have an online component, older broadcasts do not. Similarly it wouldn't be right to say "I don't know" because the station they were broadcast would be most likely be known. Therefore I'd like to propose adding the following hierarchy of formats:

• Radio
  • Analogue Radio
    • FM
    • AM
  • Digital Radio
    • DAB
    • IBOC
    • ISDB-TSB
    • DRM

I've taken this list from: https://beonair.com/types-of-radio-broadcasting

Please all see https://community.metabrainz.org/t/style-guidelines-for-bbc-radio-1-essential-mix/515760 for a longer discussion around this and the background behind this ticket.