Selecting Antennas for VHF Voice and AIS
We strongly recommend separate antennas for VHF Voice communications and AIS, rather than the use of a Splitter box. This is because Channel 16, the most important channel for Voice, and AIS, occupy frequencies at opposite ends of the VHF frequency band, so any antenna that is optimised for Voice will be less efficient at the AIS frequency, and vice versa.
Comparing masthead antenna and Splitter, with pushpit-mounted dedicated AIS antenna.
With the masthead-mount you get, theoretically, extra range, but you compromise on efficiency if you’re not using a dedicated AIS-optimised antenna. Bearing in mind that the ship you’re ‘looking at’ on AIS has an extremely high antenna, it is our view that the extra height on the yacht isn’t worth having, given the likely loss of efficiency and added potential break-down point of a Splitter. If you have two masts, great, VHF radio for voice on one, AIS on the other, but if you’ve got just the one mast, we recommend having the VHF voice antenna atop that, and the AIS antenna on the pushpit. Only if that is impossible should you consider using a Splitter.
For power boats with deck-mounted antenna, you can have a matching pair. One side for the VHF voice radio, the other side for AIS.