The other day I used Sea Tow's automated radio check system in Tampa Bay and it was kind of cool. You go to VHF channel 27 and transmit your request and in a couple of seconds a recording of your transmission will be played back. You can verify for yourself loudness and modulation. Is mostly available on the weekends when boaters are out. It may have been available for a while but the other day I just happened to pay attention as they redirected someone to channel 27.