3 interviews I did for local radio.
My first, hospital radio, was a grilling by a well informed amateur journalist and DJ who ended by playing a record of my choice – which he mocked. At the time I liked Abba. I never received any feedback from the hospital listeners who were either not there or too sick to care.
The second was on BBC local radio. It was a telephone interview on a Sunday afternoon on an issue affecting my local community. Who listens to BBC local radio on a Sunday afternoon? Lots of people. Want 2 weeks of minor local fame? Get on BBC local radio.
The third interview was for a commercial radio station. The DJ who interviewed me was again well informed because he’d asked for a briefing email before the show. The questions were fair but searching and only vaguely connected to my briefing email. However, don’t knock commercial radio; when you see them at work, they are very professional.
And radio as a promotional tool? Not sure. I think you would have to appear a lot of times to make any impact.