VHF antennas, including AIS antennas, work properly only when positioned in an upright position (vertically). On inland ships in particular, antennas are sometimes mounted on a swivelling antenna bridge to solve height problems with bridges. Attention should be given to keep the VHF antennas in the vertical position as much as practically possible because the antennas in horizontal position will cause loss of VHF communication and AIS information from other vessels in the area.