Motorola M12 Oncore User's Guide download pdf (Page 25)

Chapter 3 – Receiver Description

Motorola GPS Products - Oncore User’s Guide

Installer Caution

(Continued)

RF Shielding

The RF circuitry sections on the Oncore GPS receiver board are protected with a tin

plate shield to guard against potential interference from external sources. When a

design calls for the Oncore to be near or around RF sources such as radios, it is

recommended that the Oncore be tested and tried in the target environment to

identify potential interference issues prior to final design.

In worst case situations, the Oncore receiver PCB may require an additional

enclosure in a metal shield to eliminate electromagnetic compatibility (EMC)

problems..

Real-Time Clock (RTC)

When powered up, the RTC in the Oncore receiver will have an incorrect time unless

it was previously set and maintained by external backup power. To ensure a faster

time to first fix, the time, date, and GMT offset should be input if both the main power

and battery backup power have been disconnected.

Thermal Considerations

The receiver operating temperature range is -40øC to +85øC, and the storage

temperature range is -40øC to +105øC. The antenna operating range is-40øC to

+100øC. Before installation, you should perform a thermal analysis of the housing

environment to ensure that temperatures do not exceed +85øC when operating

(+105øC stored). This is particularly important if

air circulation in the installation site is poor,

other electronics are installed in the enclosure with the Oncore receiver PCB, or

the Oncore receiver PCB is enclosed within a shielded container due to

electromagnetic interference (EMI) requirements.

Grounding Considerations

The GT and UT Oncore receivers now have a different grounding scheme than

previous Oncore receivers for improved EMI/EMC performance. The RF shields on

both sides of the module are connected to ground at multiple points. The ground

plane of the receiver is connected to the four mounting holes.

For best performance, it is recommended that the mounting standoffs in the

application be grounded. The GPS receiver will still function properly if it is not

grounded via the mounting holes, but the shields may be less effective.

Revision 5.0 08/30/02

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Motorola M12 Oncore User's Guide Page 25