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Appendix D Performance Tests
Complete Performance Tests
D-22 Operating and Programming Guide
Test 2: 10 MHz Holdover Aging and 1 PPS
Accumulated Time Error (Unlocked)
The following tests are identical to the previous tests, with the
exception that during the actual test, the Receiver is not locked to the
GPS. However, the test must adhere to the restrictions noted below
with the specification in order for the results to be valid.
Specifications Tested
Holdover aging: < 1 x 10
-10
/day average frequency change in 24 hours
unlocked after 3 days locked operation for any 10 degrees C range
between 10 degrees C and 40 degrees C.
Accumulated time error: <8.6 us accumulated in 24 hours unlocked
after 3 days of locked operation with a fixed antenna location, any
10 degrees C range between 10 degrees and 40 degrees C.
Procedure
1 Ensure that the Receiver has been in GPS Lock mode for at least three
(3) days without entering holdover mode by typing the following
command on the terminal or computer:
:DIAG:LOG:READ:ALL? and press the Enter (or Return) key.
Verify that there are no messages to indicate that holdover mode was
started during the last 72 hours of operation.
2 Ensure that the temperature restrictions described above will be met
for the next 24 hours.
3 Connect the 10 MHz reference output from the reference 1 PPS source
(5071A or another stable, traceable house standard) to the rear-panel
Ref In of the Universal Counter, as shown in Figure D-6, to provide an
external timebase for the Counter.
4 Connect the rear-panel 1 PPS from Receiver under test to Channel 1 of
the Universal Counter.
5 Connect the 1 PPS from the reference standard (5071A) to Channel 2.
Ensure that the inputs are set to DC-coupled, 50 Ohms, and rising
edge. Set the trigger level for both inputs to 1 Volt dc.
6 Disconnect the antenna cable (N-type connector) at the rear of the
Receiver to force it into Holdover Mode.
7 Ensure that the Holdover indicator is illuminated and the GPS Lock is
not illuminated.