AIS Antennas4' Length, 4.5dB GainIn conjunction with the USCG Automatic Identification System (AIS) requirements for commercial vessels, Digital Antenna created a series of 4 AIS antennas that meet the exacting AIS frequency requirements. Designed with a low 1.5:1.0 SWR ratio from 159-162 MHz, Digital Antennas 4.5 dB gain AIS antennas offer unsurpassed durability and performance compatible with all AIS transponders.All of our antennas are made in the USA, assembled, tested and tuned by hand for maximum performance, quality and durability.All 4' AIS Antennas Feature:Powerful brass radiators Soldered connections Power directing ferrite choke bead High gloss urethane finish 316 stainless steel ferrule 4.5dB gain 800 GOLD SeriesMount: Stainless steel double female ferrule for mounting 114 threaded base Connector: Quality female SO-239 (UHF female) Cable: Not included use our VHF/AIS cables and two DA645 connectors