TrimTrac ProE Locator Technical Manual v2.0e
70
GPS Antennas
The TrimTrac ProE has an internal GPS antenna or can be used with an optional
external GPS antenna. When an external GPS antenna is first connected, the
TrimTrac ProE will not recognize that an external GPS antenna is attached until
the next time it enters the FIX State. On the other hand, if the external GPS
antenna is disconnected for five or more seconds, then the device will begin using
the internal GPS antenna immediately without first having to enter the FIX State.
Whether the device is using the internal or external GPS antenna is indicated (and
whether the device has a complete almanac) in each POSITION_REP and
STATUS_MESSAGE for which a position fix was attempted. Battery life may
be impacted when an external GPS antenna is used.
GPS Almanac Collection
When the TrimTrac ProE is used for the first time after being provisioned, the
unit may not have a complete or current GPS almanac. If the TrimTrac ProE
needs to collect or update the GPS almanac, it will do so by keeping the GPS
receiver operating in the background after a position fix is computed. This GPS
almanac collection will not interfere with the other operations of the TrimTrac
ProE. Whether the device has a complete almanac (and whether the device is
using the internal or external GPS antenna is indicated) in each POSITION_REP
and STATUS_MESSAGE for which a position fix was attempted.
GPS Almanac Loading
A current almanac can be collected from any operational TrimTrac ProE using the
PC-based TrimTrac GPS Almanac Tool. This collected almanac can, in turned,
be loaded into any other TrimTrac ProE.
Converting GPS Time (UTC), GMT and Local Times
Sample source code for converting GPS (UTC), GMT, and local times is available
on the
www.trimtrac.com
/documents partners’ page.
Orientation
When using the internal GPS antenna, the TrimTrac ProE should be in a near
horizontal position with a reasonably clear view of the horizon and sky. If
something on the vehicle—for example, the air conditioning unit on a cab or the
trailer connected to a tractor—blocks a significant portion of the horizon and the
GPS signals, the GPS receiver will take longer to acquire enough satellites for a
position fix. If the TrimTrac ProE frequently times out before completing a
position fix, try moving the TrimTrac ProE to a new location where it, or the
optional external GPS antenna, is not blocked as much.
GPS Jamming
The TrimTrac ProE should be installed as far away as possible from transmitting
antennas, including satellite communication, radar, VHF and cellular. These
transmitters may emit jamming signals that interfere with the GPS receiver’s
Summary of Contents for ProE Locator
Page 112: ...TrimTrac ProE Locator Technical Manual v2 0e 94 Figure 24 HPA Processing in TRANSMIT ...
Page 113: ...TrimTrac ProE Locator Technical Manual v2 0e 95 Figure 25 MPA Processing in TRANSMIT ...
Page 114: ...TrimTrac ProE Locator Technical Manual v2 0e 96 Figure 26 LPA Processing in TRANSMIT ...
Page 177: ...TrimTrac ProE Locator Technical Manual v2 0e 159 ...
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Page 205: ...TrimTrac ProE Locator Technical Manual v2 0e 187 Quick Reference Tables ...
Page 232: ...TrimTrac ProE Locator Technical Manual v2 0e 214 Figure 37 Control Module Wiring Diagram ...