Who Invented Radio: Guglielmo Marconi or Aleksandr Popov? (spectrum.ieee.org)

"Making a definitive claim of who was first is complicated by inadequate documentation of events, conflicting definitions of what constitutes a radio, and national pride."

What constitutes "a radio"?

Not the original patent for the radio. Later improvements to the tuner were invalidated as not being novel enough to grant patent rights to.