As stated, 453.65, and they are usually communicating over aircraft frequencies with Bangor AP. I have heard them on both. Where you live has a lot to do with how you will hear them. They switch towers a lot and there are times where I cant hear the communication do to the hole I live in. They can be on any tower from Mt Washington to Sanford to Bangor? or points north. The dispatch and the helicopter both switch depending on where the helicopter is. It isn't a simulcast system.