Racelogic VBOX II User Manual page 23

GPS antennas require a ground plane to operate correctly. Usually, the metal roof of a vehicle performs this function.
However, if a test requires an antenna to be placed off of the vehicle, then a special Ground Plane 'mushroom-style'
antenna must replace the off-vehicle antenna, as these antennas are capable of operating without a ground plane. The
Ground Plane 'mushroom' style antennas RLVBACS065 are available from your VBOX distributor.
RLVBACS065 'mushroom' type Ground Plane Antenna
https://en.racelogic.support//Product_Info/VBOX_Data_Loggers/VBOX_II_Range/VBOX_II_User_Guide/05_-
_VBOX_IISX_Single_Antenna_Placement
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