VB20SL User Guide
Page 8 of 30
When measuring slip at a specific point on a vehicle (for example over a given wheel), the primary
antenna must be placed over this point on the vehicle, whilst the secondary antenna should be
placed towards the centre of the vehicle.
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.
If only one antenna will be placed ‘off-vehicle’ then only one Ground Plane antenna need be
purchased.
Antenna Separations >2M
When the antenna separation is >2M it is advised where possible to mount the antennas as level
as possible so
that the ‘LEVEL’ option can be enabled, otherwise the RTK lock is not so reliable
and the Slip and Roll/Pitch data can drop out or become intermittent.
The VB20SL must only be used with the supplied antenna, unless instructed otherwise by
Racelogic.
GPS Antenna
The GPS Antennas supplied with the VB20SL are 3.5v active antennas. For the best possible signal
quality, it is important to maintain a clean connection between the antennas and the VBOX. Before
fixing the antennas to the VBOX, ensure that there are no dust particles in either connector.
Replacement antennas are available by contacting your VBOX distributor.
The antenna is a magnetic mounting type for quick and simple mounting to the vehicle roof. For
optimum GPS signal reception, make sure that the antenna is fitted to the highest point of the vehicle
away from any obstructions that may block satellite reception. The GPS antenna works best with a
metal ground plane underneath (eg. Vehicle roof).
Please also note that when using any GPS equipment, a clear sky view is important. Objects in the
surrounding area such as tall buildings or trees can block the GPS signal causing a reduction in the
number of satellites being tracked, or introducing reflected signals that can decrease the accuracy of
the system.
NOTE: VB20SL can struggle with maintaining an RTK lock required for Slip and Pitch
measurement if the antennas are placed too close to Roof Bars. If a poor mounting position
cannot be avoided then use Ground plane antennas, RLVBACS065.
