Maxon Telecom MM-6854 Manuel D’Utilisation

Issue 1.0

ME 820047

03/00

Page 39

This is an area, which is often overlooked and is, in fact, very important.

Cost and corner cutting are frequently observed in installations and, consequently, reliability suffers
and problems are seen.

We can only offer a few suggestions in this document, however, expert help is available from a
number of experienced installation companies.  Knowledge of the vehicle in which the equipment is
being installed is invaluable.

The majority of GSM antennas do not require an additional ground plane. However, it is important that
any antennas are installed in the best possible location and, if necessary, provided with a suitable
ground plane.

The CA8401 antenna, which Maxon sell as an accessory, is designed for mounting inside of the
vehicle.  This avoids any problems with car washes or vandalism.  Mounting instructions are provided
with the aerial.

Ideally, multiple antennas should be separated by a minimum of a wavelength (at the lowest
frequency), whilst still retaining a good ground plane for each antenna.  For instance, for a 400MHz
antenna, the ideal separation should be a minimum of 0.75m from any other antenna.

With the use of composite materials, especially on trucks, materials may have to be used to fabricate
a suitable ground plane, if required.

Note: It is important that the antenna ground is not connected to the modem ground.  This will not
happen where through-glass antennas are used.  Antennas, which are through-chassis mounting and
connect to the vehicle chassis should not be used.  Failure to observe this may result in damage to the
unit and will invalidate the warranty.

It is important that a “clean” source of power is used for the supply to the modem.  Ideally, this is
achieved by taking the supply directly from the battery terminals.  With modern vehicles, getting
access to the battery is very difficult and therefore alternative sources have to be found.  The next best
source is the main fuseboard and then around the steering column.

Frequently, either a large voltage glitch, or total loss of voltage may be observed on some trucks at
start-up.  The loss of voltage to the GSM data modem is avoided by the use of an internal battery.

It is recommended that star earthing is used for all connections to the –ve terminal of equipment.  This
avoids the possibility of earth loops.

The power supply should be in the range of +9V to +28VDC.

Maxon can supply, as an accessory, a mains power supply which is capable of powering
MM-6854 modems.  This power supply has the part number CA6823 and is a 12V, 1A power supply.

It is strongly suggested that fuses for the data modem, and any associated equipment, are located in a
place away from the main fusebox.  This is to avoid the possibility of the fuses being “borrowed” by the
driver for other uses.

A 500mA anti-surge fuse should be used for +12V powering or a 800mA anti-surge fuse used for
+24V powering.