When I say that the channels are encrypted and you can only hear one side of the converstion the reason is you are transmitting on one frequency but your radio automaticaly receives on another because the on shore operations from the telephone company tranmits on a different channel. I am very sure you can not transmit boat to boat on any of the ship to shore dual frequency channels. Your radio does not have the same frequency in transmit and receive as it does in single frequency channles such as 68 or 69. Again the reason for the clutter on the single freq. channels. The channels you have available for ship to ship communications of other than safety related (ch06) are very limited, all other channels are fairly strictly regulated and may involve problems for the user for other purposes.