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 1.51.0 SWR ratio from 159-162 MHz, Digital Antennas 4.5 dB gain AIS antennas offer unsurpassed durability and performance compatible with all AIS transponders.Customers and installers love the 500 GOLD Series easy installation connector system.