Maxon Telecom MM-6854, MM-6864 manual Installation, Antennas, Power Sources, Fusing

MM6854/64 Dual Band GSM Data Modem

7 INSTALLATION

7.1 Introduction

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.

7.2 Antennas

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.

7.3 Power Sources

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.

7.4 Fusing

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.

Issue 1.0	ME 820047
03/00	Page 39