Symmetricom 58503B, Руководство по началу работы, Страница: 60 / 90

Chapter 2 Features and Functions
In Case of a Problem
2-24 Getting Started Guide
Holdover frequency is maintained to better than ±1
×
10
−
10
per day
(phase accumulation <8.6
µ
s after 1 day). When the GPS reference
signal is restored, the Receiver automatically switches back to normal
mode of operation.
In Case of a Problem
Hours after powerup, Receiver not establishing GPS
lock
Symptom
Date, time, and position still show power-up defaults, or these
parameters are incorrect.
Receiver Position Mode = Survey.
Receiver cycling from one set of satellites to another.
No satellites consistently tracked.
Solution
Check antenna:
• Verify antenna has an unobstructed view of the sky—antenna is
not under or beside an impervious object.
• Verify antenna is connected.
• Verify antenna is connected properly:
– cable run not too long.
– cable with antenna attached neither shorted nor open.
• Verify antenna is being properly driven— Hint: (1) Connect
Tee-connector to the
ANTENNA
input; connect antenna cable to one
end of Tee. Measure a little less than
+
5 Volts from the other end of
the Tee using a digital voltmeter (DVM) as shown in Figure 2-8. If
your reading is a lot less than
+
5 Volts, you will have to determine
if the line amplifier or lightning arrester is at fault by using
conventional troubleshooting isolation techniques. If the line
amplifier and lightning arrester are good, then the antenna may be
faulty. (2) If the Receiver’s
+
5 Volts is okay, check +5 Volts at the
antenna end of the cable with a voltmeter connected between the
center conductor and shell. If insufficient voltage is present, it may
indicate that the shield of the cable is not making adequate contact
to one of the cable connectors.
• After the antenna connection has been verified, cycle power on the
Receiver to facilitate rapid recovery from the fault.