46 CFR §140.715

1. (a)Towing vessels must meet the communications requirements of 33 CFR part 26 and 33 CFR 164.72, as applicable.
2. (b)Towing vessels not subject to the provisions of 33 CFR part 26 or 33 CFR 164.72 must have a Very High Frequency-Frequency Modulated (VHF-FM) radio installed and capable of monitoring VHF-FM Channels 13 and 16, except when transmitting or receiving traffic on other VHF-FM channels, when participating in a Vessel Traffic Service (VTS), or when monitoring a channel of a VTS. The VHF-FM radio must be installed at each operating station and connected to a functioning battery backup.
3. (c)All towing vessels must have at least one properly operating handheld VHF-FM radio in addition to the radios otherwise required.