NorthStar Navigation GM1708 961XD - Manual (Page 52)

SECTION TWO - Installation
Page 42 961 INSTALLATION MANUAL Revision A
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.
Table 4: Troubleshooting the radar interface
Component Symptom Possible Solutions/Reasons
961 CONTROL HEAD The display is either knocked out
completely, or the screen flashes
after the radar is turned on (a white
flash corresponds to each revolution
of the radar, when the radar range is
set to 6 nm or above). • Stand directly in front of the display to
determine if the problem is related to
interference to the control head.
• Put the radar into “standby” mode; if the
display still flashes, a non-radar type of
interference is occurring.
• Call the Northstar Service Department
to determine if the necessary internal
radar shielding has been installed. If
yes, ensure that the 961 head (and pro-
cessor) aren’t in the direct path of the
radar aperture.
• Ensure that there’s a maximum separa-
tion between the 961 control head/pro-
cessor and the radar cables. Whenever
possible, run the cables of the radar
and the 961 on opposite sides of the
vessel.
961 PROCESSOR The display is either knocked out
completely, or the screen flashes
after the radar is turned on (a white
flash corresponds to each revolution
of the radar, when the radar range is
set to 6 nm or above). • Stand directly in front of the processor
to determine if the problem is related to
interference to the processor.
• Be sure that the processor is mounted
as far away vertically from the radome.
The best location for the processor is
out of the weather, so try to mount it in
the salon or as low as possible.
• Determine if the 961 processor has the
RF-125 shielding modification installed
(if you need assistance, call the North-
star Service Department).