Narrow 10 kHz resolution bandwidth: Check for printed-circuit board contamination. Clean the board as required.

IF Gain Compression in 10 kHz resolution bandwidth: FET transistors Q202, Q203, Q501, and Q503 can deteriorate with age. Measuring less than 0 volts on the FET source indicates a bad FET.

ATTEN 1 0 d B

 

R L 0dBm

10dB/

B R O K E N SYMMEbTRY

\

\

C E N T E R 300.0000MHz

 

S P A N 100.0kHz

* R B W 3.0kHz

V B W 3.0kHz

SWP 70ms

S K 1 8 4

Figure 9-15. Faulty Crystal Symmetry

Step Gains

Refer to function blocks B, H, and I of A5 IF filter schematic diagram (sheets 1 of 3 and 2 of 3) in the HP 8560 E-Series Spectrum Analyzer Component Level Information.

1.On the HP 85623 spectrum analyzer, press (PRESET), [SPATJ), ZIZRO SPAIN , (-1, and 10.

2.Press LCAL) and IF BDJ OFF.

3.Disconnect W29 (coax 7) from A5J3 and W27 (coax 3) from A5J5.

4.Inject a -5 dBm, 10.7 MHz signal into A5J3.

5.Monitor the output of A5J5 with another spectrum analyzer.

6.Simultaneously decrease the signal generator output and HP 85623 spectrum analyzer reference level in 10 dB steps down to a -50 dBm reference level.

7.At each step, the signal displayed on the other spectrum analyzer should be close to +lO dBm. (More subtle IF gain problems might require smaller signal generator and reference level steps.)

8.Reconnect W29 to A5J3 and W27 (coax 3) to A5J5.

IF Section 9-31

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Agilent Technologies 856290216 service manual Step Gains, Faulty Crystal Symmetry