The purpose of this article is to provide background information and detailed instructions on how to determine if it is required to install the external GPS Antenna on a MiX 4000.
The new generation hardware uses the latest GNSS devices from u-blox that can concurrently receive positions from more than one space-based satellite positioning systems. The MiX 4000 for example uses the MAX-8Q that has concurrent reception of up to 3 GNSS (GPS, Galileo, GLONASS, BeiDou). Both the USA maintained “Global Positioning System” (GPS) and the Russian “Global Navigation Satellite System” (GLONASS) systems are therefore supported and each can provide global coverage.
In about 80% of installations, the internal antenna should provide sufficient tracking and accuracy and since it is a lower cost and also easier to install, this should be the default choice for any new installation.
There are however a few situations where the install position or other vehicle features will prevent the GPS from having a clear view of the sky or to obtain a 3D lock and in these cases, it will be required to fit the external GPS antenna.
Note that the external antenna is an active antenna (and physically bigger) that can be placed in an ideal position to face the sky, so it will always outperform the smaller and passive internal antenna (with no amplification) even if the unit is placed in the same position.
The goal of this document is to help installers determine when an external GPS antenna is required and when the internal antenna is sufficient.
What can influence the performance of the internal antenna?
The internal antenna is a passive patch antenna (with no amplification) that sits on the top of the PCB and the following scenarios can influence the performance:
- If the unit is installed upside down (the antenna is pointing to the ground).
- If the unit is installed vertically (the antenna is pointing to the sides/front/back of the vehicle).
- If the unit is installed on one of its sides (antenna is pointing to the sides/front/back of the vehicle).
- If the unit is installed inside another box (fire/tamper protection).
- If the unit is installed in the dash close to/or behind metal plates.
- If the unit is installed in a metal enclosure (e.g. under the bonnet/in boot).
- If another active antenna (that transmits in the same frequency range) is installed in close vicinity.
- If the unit is installed behind a metal grid or mesh.
How to test if the internal antenna is good enough?
Place the unit in the position where you plan to install it and power it up and take the ignition wire to 12V to ensure that the unit is in a trip.
Connect with the MiX Techtool to the unit and check the GPS lock state. If the unit does not display a 3D lock after 60 seconds (1 minute) after ignition ON, then the internal GPS antenna will not be good enough and you must fit an external GPS antenna.
See the pictures below for examples of a system with and without GPS lock:
Internal Antenna
The picture below indicates that the internal patch antenna is placed in the left and front of the unit:
This means that the unit must be installed with this side pointing to the roof of the vehicle in order for the GPS to have a clear view of the sky.
If the unit is installed on one of its sides or vertically, the internal antenna will not have a clear view of the sky and the performance will be compromised.
The internal antenna is also a passive antenna and smaller than the external antenna, which means that the external antenna will always outperform the internal antenna even if they are installed in the same location.
The full specification for the internal patch antenna can be found in the attached document, MiX 4000 Internal Antenna.pdf at the end of this article.
External Antenna
The external antenna in the picture below is an active antenna with a bigger antenna surface and has a 5m cable so that it can always be installed in the best position where it has a clear view of the sky.
The external antenna, therefore, provides a superior GPS signal to the MiX 4000 and will always outperform the internal antenna in terms of:
- Number of satellites
- HDOP and VDOP
- Time to lock
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