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06 - VB3i Dual Antenna Setup


VBOX Manager has been developed to control the operating functions of a VB3iSL. This section describes how to setup your vehicle with two antennas.


Within the Dual Antenna menu, select the enable option in order to see the full dual antenna system menu, with a tick shown next to enable.

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Antenna Separation

The most important factor for dual antenna testing is the correct configuration of the separation distance between the two antenna centre points. This allows the VB3iSL / VBSS100SL to acquire and maintain dual antenna lock. The physical separation distance between the two antennas should be measured as accurately as possible, and entered in to the Separation option of the Dual Antenna menu.

To provide consistent reference, the two antennas should be aligned with the gold antenna connectors pointing in the same direction.  This then allows a connector-to-connector physical reference measurement to be made.

When the antennas are setup on an un-even plane, and not perfectly level, the hypotenuse (3D distance) measurement should be used.

Where possible, antennas should be placed on a level plane.  A maximum of 10° different between the primary and secondary antenna is permitted.  

antenna_separation_1.png (1).png antenna_separation_2 (1).png antenna_separation_3 (1).png antenna_separation_4 (1).png

Note: Whenever the physical antenna separation is altered, this should be changed accordingly within VBOX Manager. 

Roll Mode (optional)

The VB3iSL / VBSS100SL allows the user to separately test roll and pitch measurements during their testing. By default, the VB3iSL / VBSS100SL will be setup for pitch determination. If the user wishes to setup their antennas across the width of the car to measure roll angle, then the Roll Mode option must be toggled in the Dual Antenna menu. Click this option to toggle between Pitch Mode (no-tick), and Roll Mode (tick).

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roll mode 5.png

Align Antennas

To measure the slip angle with the most precision, try and get the alignment of the antennas as close as possible to the centreline of the vehicle. Any residual errors in this alignment can be removed using the AUTO ALIGN feature available in VBOX Manager.

  align_antennas_1.png (1).png align_antennas_2 (1).png  


The calibration process requires the driver to drive in a straight line for a short period of time, whilst maintaining a constant speed, greater than 25 km/h.
Note any existing alignment offset from a previous setup should be removed by using the CLEAR function. This should be completed before the AUTO ALIGN.
Note that any camber on the road or a strong side wind will affect this alignment.

The calculated alignment offset will be applied to the determined heading of the secondary antenna (True Heading). The True Heading Offset will be displayed in the header comments section of a recorded .vbo, when viewed in a text editor suite, such as Notepad++.



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Selecting the CLEAR option will remove any offset applied to the slip channel.

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 Note: You must have dual antenna lock to be able to perform this calibration.


Level Antennas

The Pitch measurement uses the relative height difference between the antennas to calculate the Pitch Angle relative to the ground. If the roof of your vehicle is not perfectly flat in relation to the ground, then this will show up as a Pitch offset. You can automatically remove any offset by performing the AUTO LEVEL feature available on VBOX Manager.

Note that any existing antenna level offset from a previous setup should be removed by using the CLEAR function.  This should be completed before the AUTO LEVEL.

It is recommended that you perform the AUTO LEVEL on a flat, level section of road.

level_antennas_1 (1).png level_antennas_2 (1).png

 Selecting the Clear option will remove any offset applied to the pitch channel.

level_antennas_3 (1).png

Slip Angle Translation

In twin antenna mode you may wish to take slip measurements from other locations on the vehicle, for instance the centre of gravity or slip over the wheels. This can be set using the SLIP TRANSLATION function in VBOX Manager. The five additional locations are set using longitudinal and lateral offsets from the primary antenna location (antenna 1 in the picture below). Longitudinal translation offsets should be defined as positive when forward of the primary antenna, negative when behind the antenna. Lateral translation offsets should be defined as negative when to the left of the antenna, positive when to the right.

VB3iSL - IMU assistance: when an IMU module is connected to the VB3iSL, the yaw rate channel will be used in the calculated slip channels, as the signal to noise ratio is much lower than the GPS derived yaw rate. Therefore no extra noise is added during the slip translation process. 

VBSS100SL - Gyro assistance: VBSS100SL has an integrated gyroscope which requires the unit to be mounted flat. The Gyro Yaw Rate will be used in the calculated slip channels as the signal to noise ratio is much lower than the GPS derived yaw rate. Therefore no extra noise is added during the slip translation process. 

slip_translation_1.png (1).png slip_translation_2 (1).png slip_translation_3 (1).png slip_translation_4 (1).png


slip translation 5.png

In section 1 on the diagram below there is a lateral offset between the primary antenna and the target area for slip measurement. Same again for section 2, there is a longitudinal offset. These offsets will need to be applied by VBOX Manager (ensure you apply the correct sign when entering the offsets).  

slip translation 6.png

Each calculated slip point will require two offsets, LAT & LNG (or lateral & longitudinal), for the VBOX to calculate the channels correctly. Note: if the primary antenna moves the offsets will need to be measured again, for example swapping between a pitch and roll setup.

slip translation 7.png

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