Simrad VHF/AIS Antennas

Antenna height, gain and cable loss

VHF and AIS range depends more on antenna height above the waterline than on transmitter power, since both are line of sight systems; a masthead antenna on a sailing boat will generally outperform a taller-gain antenna mounted lower on a powerboat. Higher-gain antennas flatten their radiation pattern, which extends range on a stable boat but can work against you on a boat that rolls heavily, since the signal can point above or below the horizon during the roll rather than staying level.

Cable run and connector quality matter as much as the antenna itself; a long run of thin coax or a poorly fitted PL259 connector can lose more signal than switching to a higher-gain antenna would gain back. Combined VHF and AIS antennas simplify installation where mast space is limited, though a dedicated antenna for each avoids any compromise in tuning across the two frequency bands. Check your existing cable run before assuming a new antenna alone will fix a range problem.