I cannot seem to find any information on this subject for the United States. Are there any public bands one might be able to use for an AM transmitter? Is it legal to transmit over an unused AM radio channel if your transmitter has a really small output power? My idea is to attempt a wireless intercom circuit in my own house, but I don't want the FCC knocking at my door or to get into any legal trouble if I can succesfully accomplish this. My circuit will just operate on a 9V battery or less.