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Quick Start - VBOX 3i Dual Antenna

For Slip and Pitch measurements

Required equipment (All supplied as standard unless specified)



2 x GPS & GLONASS antenna RLCAB001 or RLCAB066-2 (for PC connection) Tape measure
Cigar lighter 12 V adapter lead VBOX Manager + RLCAB005-C Blank compact flash card Laptop PC (not supplied)

 1. Place VBOX in vehicle then mount the GPS/GLONASS antennas on the vehicle roof in-line with the direction of motion, and clear from any obstructions. Connect the primary antenna (normally at rear of vehicle) to port A, and the secondary antenna to port B on the VB3iSL.

Note: It is important to connect the antennas to the VB3iSL before power is connected. The VB3iSL adjusts the signal gain to the antenna based on the current incoming GPS signal strength.


See these articles if having difficulty obtaining satellite lock: Satellite elevation mask      GPS Cold start


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2. Note that any alignment error can be zeroed using the ‘ALIGN ANTENNAS’ option on VBOX Manager.

3. Make sure the antennas are rotated so the wires exit in the same direction as each other.

4. Accurately measure separation distance to the nearest 5 mm, for best accuracy measure from the point at which the cable exits the antenna.

5. For normal operation, place the primary antenna (Socket A) at the rear of the car, and the secondary antenna (Socket B) at the front. All measurements are made from the primary antenna.

6. Power up VB3iSL.

7. Connect VBOX Manager to VB3iSL port dedicated to Racelogic CAN bus (determined in CAN tab of VBOX Tools Setup or VBOX Setup).

8. Go into SETUP>DUAL ANTENNA->SEPARATION and enter the separation of the antennas

9. Allow the unit time to acquire full satellite lock.  The number of satellites in view is indicated by the SATS LED; the total of green flashes indicates GPS count, whilst an orange flash indicates the GLONASS satellite count.  If the VBOX has not been used for a long time, or the location where it is being tested has changed drastically, a GPS coldstart may be required.

10. Move forward in a straight line, in an open area, and the DUAL LED should turn green to indicate dual antenna lock has been obtained. Once the DUAL LED is lit (green) you are ready to begin testing.
Note: It takes around 30-60 seconds to reach full accuracy on the pitch measurement.

For Slip and Roll measurements

1. Follow the same steps as ‘Slip & Pitch measurement’ guide, but mount the antennas 90° to the true heading of the vehicle such that the primary antenna (Port A) is on the left hand side of the roof.  Minimum recommended separation between the antennas is 0.5m on a level plane, but the greater the separation distance, the better the accuracy.

2. Using VBOX Manager, go into SETUP->VBOX->DUAL ANTENNA-> and tick ‘ROLL MODE’.

3. Go into SETUP->VBOX->DUAL ANTENNA->SEPARATION and enter the separation of the antennas.

4. Try to avoid placing the antennas close to the edge of the roof as this may result in poor dual lock. This is because reflections from the ground will disturb the signals.

5. Driving forward should now bring on the green DUAL LED.

Note: If the IMU integration feature of the VBOX3i is to be used refer to this article ‘IMU Integration’ 

Dual Antenna Placement

Careful attention must be paid to placement of the antennas.

It is essential that the separation of Antenna B from Antenna A is exactly the same as the separation value set inside the VBOX 3i via VBOX Manager, or within VBOX Setup. If the separation is incorrect, data may not be given or may be inaccurate.


The measured distance between the antennas should be the 2D distance between the antennas as viewed from above. It is not the straight-line distance between the antennas regardless of the mounting angle.


The supplied tape measure will help ensure an accurate antenna separation.


Antenna A is the primary antenna, from which all calculations are based. Therefore the primary antenna should be placed relative to where you wish to make your measurements from.  For example, If you wish to make measurements from the centre of the vehicle, this can be achieved by placing the primary antenna at the centre of the vehicle or translating the position using the slip angle translation function in VBOX Manager.

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