HP 8562E - Page 345

*ATTEN 10dB
RL 0dBm
lOdB/
I I I
CENTER 300.0000MHz
*RBW 1.0MHz
VBW 1 .BMHz
SPAN 3.000MHz
SWP 50ms
SK183
Figure 9-14. Faulty LC Pole
30 kHz Resolution Bandwidth Problems
Shape factor too high: Shape factor is the ratio of the 60 dB bandwidth to the 3 dB
bandwidth. Shape factor should be less than 15:l. If one of the LC poles malfunctions, the
shape factor may be the only indication of the failure. Isolate the non-functioning pole with
the IF signature. Region E of Figure 9-8 illustrates the four LC-pole adjustments. Take
several signatures to examine the LC-pole adjustments. If one of the four sections of Region E
is consistently longer than the others, the corresponding LC pole is faulty.
IF gain compression: FET transistors Q301, Q303, Q700, and Q701 can deteriorate with age.
Measuring less than 0 volts on the FET source indicates a bad FET.
Bandwidth too wide: Check for contamination on the printed-circuit board. Clean the board
as required.
3 kHz and 10 kHz Resolution Bandwidth Problems
Asymmetric Filter Response: Check the crystal symmetry control with the following steps:
1. Press (KZZiJ
2. Set the HP 85623 spectrum analyzer controls as follows:
Resolution bandwidth
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 kHz
Span
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100kHz
Center frequency
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
3. On the HP 85623 spectrum analyzer, connect the 300 MHz CAL OUTPUT to the INPUT
5os1.
4. A trace similar to Figure 9-15 indicates a failed crystal-symmetry circuit.
9-30 IF Section