1
MHz
Resolution
Bandwidth
Problems
Check the crystal shorting switches as follows:
1. On the HP 85623 spectrum analyzer, press
(-1
and set the controls as follows:
Resolution bandwidth
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 MHz
Span
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500kHz
Center frequency
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
2. On the HP 85623 spectrum analyzer, connect the 300 MHz CAL OUTPUT to the INPUT
500.
3. If the trace flatness is not within 2.5
dB,
a failure probably exists.
4. A trace similar to Figure 9-13 indicates a crystal short failure.
5. Press (SPAN to set the spectrum analyzer to 3 MHz. A trace that slopes across the screen
(see Figure 9-14) indicates a failed LC pole. To isoiate the broken pole refer to the shape
factor information in “30 kHz Resolution Bandwidth Problems.”
+ATTEN
10dB
RL
0dBm
lBdB/
CENTER
300.0000MHz
SPAN
500.0kHz
*RBW
1.0MHz
VBW
1.0MHz
SWP 50ms
SK182
Figure 9-13. Faulty Crystal Short
IF Section 9-29
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