Chapter 9 441
IF Section
Performance Test Failures
Performance Test Failures
Failures in IF-Section-related performance tests may be investigated
using the following information.
IF Gain Uncertainty Performance Test
Failure of this performance test indicates a possible problem with the
8564EC or 8565EC spectrum analyzer IF gain circuits. Assuming
no major IF problems causing IF adjustment errors, IF gain problems
in the first 50 dB of IF gain (REF LVLs of 0 dBm to −50 dBm with 10 dB
ATTEN) are a result of faults on the A5 IF Assembly. IF gain problems
in the next 60 dB of IF gain (REF LVLs of −60 dBm to −110 dBm, 10 dB
ATTEN) result from log amplifier faults on the A4 assembly.
A signal level of −5 dBm is required at input (A5J3) for displaying a
signal at top screen with 10 dB input attenuation and a 0 dBm
reference level.
Isolate IF gain problems on the log amplifier assembly (A4) with the
following steps:
1.On the 8564EC or 8565EC spectrum analyzer, press
PRESET,
SPAN, ZEROSPAN, FREQUENCY, 1 GHz, AMPLITUDE, −50 dBm.
2. Press
CAL and IF ADJ OFF.
3. Disconnect cable W27 (coax 3) from A5J5 and connect cable W27 to
the output of a signal generator.
4. Set the signal generator controls as follows:
Amplitude ................................................................ +10dBm
Frequency ............................................................... 10.7MHz
5. Simultaneously decrease the signal generator output and the
8564ECor8565ECspectrumanalyzerREFLVLin10dBsteps.
The signal displayed by the spectrum analyzer should remain at the
reference level for each step. If the signal deviates from the reference
level, troubleshoot the video offset circuitry on the A4 assembly.
6.Repeatsteps1through5withthe8564ECor8565ECspectrum
analyzer set to linear.
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