Actual terrestrial radio station or an web streaming station?
If it's an actual terrestrial radio station (like a college radio station), then you run a lot of risks airing live callers without a delay unit. Many radio stations use VoxPro to record and digitallly edit on the fly.
If it's a streaming web station, then it depends on your broadcast setup. Are you using a physical board/mixer, or are you just plugging microphones via USB into your laptop?