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RACELOGIC Support Centre

02 - Speed Sensor GPS Antenna


The GPS antenna supplied with the VBSS is a 5 V active antenna. For the best possible signal quality, it is important to maintain a clean connection between the antenna and the Speed Sensor. Before fixing the antenna to the VBSS, ensure that there are no dust particles in either connector. Replacement antennae are available by contacting your Racelogic 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 (a metallic vehicle roof is perfect for this).

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 that clouds and other atmospheric conditions do not affect the VBOX’s performance.


GPS antennas require a ground plane to operate correctly. This helps to reduce unwanted reflections of the GPS signal caused by nearby objects, and usually the metal roof of a vehicle performs this function. However, if a test requires an antenna to be placed either off the vehicle, or on a vehicle that does not have a metallic roof, a special ground plane antenna must be used. This has an internal ground plane and can operate perfectly without the need for mounting on a metal surface. Ground plane antennas are available from your Racelogic distributor.

Satellite Elevation Mask (dual antenna units only)

This feature can be used to improve GPS signal quality when nearby obstacles like trees and building are reflecting or temporarily obscuring the signal from satellites at low elevation. Raising the mask will cause the GPS engine to ignore satellites below the mask angle, so must be used carefully as it also reduces the total number of received satellites. 

The elevation mask angle can be changed in the GPS tab within VBOX Setup Software or using a VBOX Manager.

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GPS Coldstart

A GPS coldstart may be required when:

  • The GPS engine has locked up.
  • VBSS is struggling to acquire satellite lock

A GPS coldstart forces the GPS engine to reset its downloaded almanac of current satellite positions. This can be useful if the VBSS is having trouble locking onto satellites, which typically occurs if the unit has not been used for several weeks or if it was last used a long distance (over one thousand miles) away from the current location.

After performing a GPS coldstart leave the VBSS powered up in a static location where the antenna has an unobstructed view of the skies until the ‘GPS’ LED becomes solid green.


How to perform a coldstart

There are two ways that a coldstart can be performed on the Speed Sensor.
  1. Software: Connect the Speed Sensor to PC using the RS232 connector of the RLCAB093 loom. Open VBOX Setup software, select the Speed Sensor from the drop down menu and connect to this unit. From the General tab, there is a button to perform a GPS Coldstart. The LED's on the Speed Sensor will all turn red, and return to normal function when the coldstart procedure has completed.
  2. Digital Input: If the Speed Sensor's Digital Input is configured to Lap Pulse mode, a coldstart can be performed by grounding the input while connecting the Speed Sensor to power. If done correctly, the LED's on the Speed Sensor will all turn red, and return to normal function when the coldstart procedure has completed.
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