NorthStar 951X Installation Manual page 48

SECTION TWO - Installing the unit
b. Testing the GPS portion of the splitter and a combo antenna: When using a combo antenna and split-
ter, the splitter gets 7.75 VDC from the beacon receiver, and then feeds the combo pre-amp with that
same voltage level. The splitter must have this 7.75 VDC supplied to the differential port in order for
the GPS and the differential signal to be passed through the splitter. To test the GPS portion of the
combo antenna, disconnect the splitter and plug the combo antenna directly into the GPS BNC con-
nector (provided that the 5.5 VDC is present). This troubleshooting technique effectively eliminates
the splitter from the equation. If the splitter is bad, GPS may not work when connected normally
(provided that the 7.75 VDC from the beacon receiver is present). Note that the combo antenna
should never be plugged directly into the GPS port under normal circumstances because the voltage
feeding the amplifier is too low and this will result in low GPS signal levels being sent to the GPS
receiver.
c. The beacon receiver (8500) supplies the 7.75 VDC to the 8410 (in the case of a whip-type antenna
installation), or the splitter (in the case of a combo antenna installation), which in turn feeds the
combo antenna.
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951/952 INSTALLATION MANUAL Revision B