User`s guide

Chapter 3 - Receiver Descriptions

The antenna status information is output in the following I/O messages:

• @@Ha(12 Channel Position/Status/Data Message)

• @@Hb (12 Channel Short Position Message)

• @@Ia (12 Channel Self-Test Message).

NOTE: Detection of an under current situation will

not prevent the M12+ from operating. The M12+ will

continue to operate normally, but will raise the error

flag in the three messages, indicating a possible

antenna problem.

A chart of the typical output voltage vs. the load current is shown below in figure 3.2. Note that

there is some drop to the output voltage as higher currents are drawn due to IR losses across the

current sense resistor and pass transistor. The system engineer should consider this drop if the

coax run to the antenna is going to be long, and/or the gain of the antenna being used is

adversely affected by lowered input voltage. Note that the M12+ can accept any voltage from

+2.5 to +5.5 Vdc on the antenna bias pin (Pin 9.)

Figure 3.2 M12+ antenna drive circuit performance

Motorola GPS Products - M12+ User's Guide Revision 6.X 09FEB05