I've ever seen that used a condensor.
It's almost always, always, always, an RE-20 or SM-7.
I don't know anything about the Heil, but I would guess an SM-57 also, unless you're looking at used, which changes the playing field somewhat, but probably not much.
That $100 limit is really going to, well, limit your choices.
I've heard of guys having success with the MXL V67 as a voice-over mic, but that's an application that's more different from yours than you would think.
What kind of radio show, as in one host, one guest, a group discussing sports, a morning comedy team thing? How many people are going to be on the air in the same room at the same time? Is it going to be the same people every time, or will you have a rotating group of guests? What I'm getting at there is can you pick a specific mic for the person, or will the same mic have to suit a bunch of different people?
Here's what you have to take into consideration:
Voices
Meaning, what works best for a big loud guy might not work best for a quiet, sultry girl. Those are extremes, but you get the idea.
Location
If it's just one person, or one person interviewing a guest, then you can take more control over the environment to exclude extraneous noise, in which case you might be able to get away with using a condensor. If it's a bunch of guys cutting up, you're going to want dynamics, or all you'll hear is a bunch of background noise.
Just my opinion.