Symmetricom Z3801A, User Manual

Page: 42 / 98

Chapter 2 Features and Functions
In Case of a Problem
2-12 User Guide
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 Receiver’s rear-panel
ANTENNA J1
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 2-1. 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 Re5 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.
NOTE
Remove the Tee connector and restore antenna connection as loading of
the Tee connector will prevent proper reception of the GPS signal by
the antenna.