Micom 3T Operations Instructions download pdf (Page 123)

Using the MICOM-3 GPS Receiver

105

Therefore, after turning a GPS receiver on for the first time after a long period of inactivity, it is

essential to let the GPS receiver operate continuously for at least 15 minutes, to enable it to collect

updated almanac data. After this initial 15-minute interval, a GPS receiver can relatively rapidly

acquire the satellites and calculate its position; thereafter, a GPS receiver must remain on only for a

few minutes in order to be able to provide navigation data.

The internal GPS receiver is always powered when the transceiver is turned on. Therefore, if the GPS

antenna is connected, the GPS receiver can start the acquisition process as soon as the transceiver is

turned on, and can then track the satellites continuously. Turning the MICOM-3 transceiver off will

force the GPS receiver to reacquire the satellites.

GPS Antenna

Antenna Description

The GPS antenna is a compact active omnidirectional antenna with magnetic

mounting, which attaches easily and firmly to vehicle’s steel body parts, even

when painted. The antenna will not attach to non-magnetic alloys (e.g.,

aluminum alloys), nor to parts made of composite materials (e.g., fiberglass).

The antenna connects to the GPS connector of the MICOM-3 transceiver through a 5-meter (15 feet)

long coaxial cable, which is part of the antenna. This cable carries both DC power for the antenna,

and the received GPS signals.

The antenna is 42 mm wide by 50.5 mm long by 13.8 mm high (1.65”×1.99”×0.55”), and it requires

a minimal ground plane of 60 by 60 mm (2.36”×2.36”) to provide the specified performance.

Selecting a Proper Location for the GPS Antenna

GPS satellites transmit their special signals in the 1575 MHz range: such signals do not penetrate

conductive or opaque surfaces. When selecting the location of the GPS antenna, you should also be

aware that strong local interference as well as reflections from nearby objects may disrupt normal

reception and degrade the signal quality.

Thus, GPS antennas should be installed on horizontal surfaces, in a place that provides a clear view of

the sky, which, in as far as possible, is not obstructed by large objects. For example, the roof of the

passenger’s cabin is a good place for the GPS antenna.

Moreover, you should not park the vehicle under dense foliage or other cover, for example, in a

garage, if you want to get a position fix from your GPS receiver.

Note

When the GPS antenna is installed on a metal surface for prolonged periods, care

must be taken to insulate the antenna, to prevent galvanic corrosion.

Installing the GPS Antenna

Before starting, select a good location for the GPS antenna and plan the route for the cable

connecting it to your transceiver. The cable route should be selected in the same way you would

select the route for antenna cables: however, never run the GPS antenna cable in parallel to the

transceiver’s cables!

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Micom 3T Operations Instructions Page 123