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VHF antenna recommendations for AIS receivers and Class B transceivers - Chuck - Raymarine - Moderator - 03-24-16 12:56 PM
VHF antenna recommendations for AIS receivers and Class B transceivers
Some signal loss will generally result from the addition of any coupler, VHF extension cable, or antenna splitter installed between a VHF receiver/transmitter (ex. AIS receiver/transceiver, VHF radio) and its antenna. Accordingly, when seeking maximum performance from a VHF radio and AIS receiver/transceiver, it is recommended that each be interfaced to its own dedicated antenna onboard the vessel. However, NMEA recommends that VHF antennas not be installed within 4' of one another to prevent damage from reception of excessive signal to the receivers of the connected devices. Depending upon the design / layout of the vessel, it may accordingly not be possible to install more than one antenna on the vessel and and adhere to the recommended minimum spacing for VHF antennas (ex. sailing vessels where the VHF cable is installed atop the mast, etc.). In such cases, a Class B AIS antenna splitter (ex. AIS100, etc.) may be installed to support use of a single VHF antenna to support both the needs of an AIS receiver / transceiver and a VHF radio.
Raymarine has not specified a maximum gain restriction for VHF antennas which will be interfaced to AIS receivers and VHF radios which have been designed to additionally function as a AIS receiver (ex. Ray70, Ray260, etc.). However, black box Class B AIS transceivers (AIS650, AIS500, etc.) should be interfaced to a VHF antenna having a maximum gain of -3 dB. Should a Class B AIS splitter be installed onboard, the connected VHF antenna would not be subject to the maximum gain restriction specified above.
RAYFAQ#