"The radio" is sort of like a half-duplex analog wi-fi WAN. "A radio" refers to the hardware one uses to hook up to "the radio" network. I know, the terminology full of obtuse colloquialisms.
My GF at the time asked me why I always had the same mix tape* and I told her if my tape deck** worked, we could listen to more than three different bands.
I assume radio is still as shitty and monotonous.
*I'm old.
** This was basically an analogue memory stick. CRAZY I KNOW!