Raymarine RAY91 Installation And Operation Instruction Manual page 120

• If there is no change in the radio's audio noise then the device is not causing RF interference.
Note: If RF interference is present then it is likely that both VHF and AIS reception are being
degraded by the device.
Multiple antenna installations
Important additional considerations when installing multiple antennas.
To prevent potential channel interference when installing two or more VHF radios on the same
vessel, ensure that the antennas are located at least 2.4 m (8 ft.) away from each other.
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