Nortel DualMode 800, Maintenance Manual

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5-4 Master Oscillator tests
411-2051-500 Draft 00.01 November 1999
Oscillator frequency test procedure using TRUs
This test is to be used to test frequency on TRUs:
1. Select and offline a TRU to use for the test.
2. Connect the interface terminal to the RS-232 port on the front panel of the
TRU under test. See Chapter 11, DualMode Radio Unit Tests, in this
manual.
3. Set up TRU for test (refer to Chapter 11 in this manual).
HSMO frequency test — transceiver carrier method
This test ensures that the HSMO is operating at the assigned frequency of 4.8
MHz
±
1.2 Hz. See Figure 5-2 for set-up.
Note: The measured frequency deviation from the assigned channel may not
fall within the
±
0.25 PPM specification. This is due to the following:
• IFR accuracy at
±
0.20 PPM translates to
±
175 Hz uncertainty
• a +100 Hz offset to ensure proper baseband operation
These translate into a slightly different deviation measured with the IFR1600:
• -75 to +275 Hz good
• -165 to +365 Hz questionable
• beyond above swap
Step Action Observation
1 Ensure that the communication monitor can
listen to the TRU under test by either the
sniffer or through an antenna.
2 Set the communication monitor to monitor
the forward channel under test.
3 Use the frequency meter/frequency error
meter to measure the offset.
±
220 Hz of the assigned frequency
4 Record the assigned frequency (in MHz) and
the frequency error (in Hz) on the test forms.
5 If the results are questionable then repeat for
at least one more transceiver.