18
GPS Antenna and Cable Information
4.2
Verifying Antenna and Cable Operation
Proper antenna and cable operation may easily be verified after installation.
If the FAULT LED
is ON, indicating that a fault exists, press the STATUS key for a fault message (see Table 2.2).
Also, the antenna itself has a two-color Operate LED located at the base of the antenna to signal
operating status. GREEN indicates proper operation (i.e. it is getting the correct voltage); AMBER
indicates improper operation (i.e. the voltage is low).
4.2.1
GPS Signal Strength
Use the SR command through a terminal program to view the receiver status. SR returns latest
receiver status, which includes the GPS signal strength. See Receiver Status under Section 10.3.6.
4.2.2
Checking the Antenna Voltage
A more comprehensive antenna test is to apply 5 Vdc to the antenna, through F connector (center
positive). The Arbiter antenna (P/N AS0087800) should draw 30 mA. The GPS clock provides a
+5 Vdc signal at 30 mA nominal, which is carried through the antenna cable to the GPS antenna.
Without the signal, the antenna and the GPS clock will not synchronize with the Global Positioning
System, and can generate an out-of-lock alarm if the Out-of-Lock feature is enabled.
4.2.3
Power Supply Check
The Antenna Voltage test (above) actually tests the main power supply voltage. The clock should
provide between 4.9 and 5.1 Vdc to the antenna.
4.2.4
Checking the Antenna Resistance
Checking the internal resistance of the Arbiter GPS antenna is not as useful as checking antenna
current mentioned above. Antenna resistance measures several megohms with meter probes at one
polarity and less so if you change the meter probe polarity.
4.3
GPS Surge Arrester
Figure 4.4 illustrates the GPS surge arrester kit (P/N AS0094500), which is mounted in line with
the antenna cable. The surge suppressor has two female F connectors, which are bidirectional, and
two ground lugs with hardware for connecting to a solid ground.
Figure 4.4: GPS Surge Arrester
Antenna
Receiver
Surge Arrester/Grounding Block
AS0094500A