47 C.F.R. § 80.866 Spare antenna.
Title 47 - Telecommunication
A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a single-wire transmitting antenna of the same length and must also include suitable insulators.
Title 47: Telecommunication
PART 80—STATIONS IN THE MARITIME SERVICES
Subpart R—Compulsory Radiotelephone Installations for Vessels 300 Gross Tons
§ 80.866 Spare antenna.