Agilent Technologies 856290216 service manual KHz if Filters, MHz if Filters

2.If an FM signal cannot be demodulated, perform the Demodulator Adjustment procedure. If the output of A4C707 cannot be adjusted as described in the Demodulator Adjustment procedure, troubleshoot the FM Demodulator or Audio MUX circuits on A4.

4.8 kHz IF Filters

Refer to function block N of A4 Log Amplifier Schematic Diagram (sheet 3 of 4) in the HP 8560 E-SeriesSpectrum Analyzer Component Level Information.

Problems with the 4.8 kHz filters can result in spurious signals appearing 2.88 kHz to

3.52kHz above the frequency of the desired response. Also, ERR 536 RBW <300 may occur when problems exist with the 4.8 kHz IF filters.

Measure the passband of the 4.8 kHz IF filters as described in the following procedure.

1.On the HP 85623 spectrum analyzer, press [CAL), IF Al3J UFF , (SPAN), and 600 (Hz.

2.Disconnect W27 from A4J3 and inject a 10.7 MHz signal of -20 dBm into A4J3.

3.Fine-tune the frequency of the signal generator to center the signal on the screen. Set the signal generator to sweep one 2 kHz span about this center frequency. Press (mSWP) on the HP 85623 spectrum analyzer.

4.Set another spectrum analyzer, such as the HP 8566A/B, to 4.8 kHz center frequency and 2 kHz span.

Caution If a dc block is not used, damage to the HP 8566A/B results. The

HP 8566A/B and many other spectrum analyzers have dc-coupled inputs and cannot tolerate dc voltages on their inputs.

5.Connect the VIDEO OUTPUT ( rear panel) of the HP 85623 spectrum analyzer through a 20 dB attenuator and dc block to the input of the HP 8566A/B. Set the sweep time of the HP 8566A/B to 10 seconds.

6.Set the HP 8566A/B t o single trigger and press TRACE A CLEAR-WRITE . Trigger a sweep of the HP 8566A/B and the signal generator simultaneously. The HP 8566A/B shows the passband of the 4.8 kHz IF filters. The 3 dB bandwidth of the filters should be 1.2 kHz.

The passband of the filters should be flat within 2 dB over 800 Hz.

7.Reconnect W27 (coax 3) to A4J3.

10.7MHz IF Filters

1.Press (PRESET], (FREQUENCY), 300 (MHz), (SPAN), 600 (Hz), (CAL), and IF BDJ OFF.

2.Disconnect W29 (coax 7) from A5J3. Set the signal generator for a 10.7 MHz signal at -50 dBm and connect it to A5J3.

3.Fine tune the frequency of the signal generator to center the signal on the HP 85623 spectrum analyzer display. Set the signal generator to sweep one 2 kHz span about this center frequency.

4.On the HP 85623 spectrum analyzer, press (-1.

5.Disconnect W27 (coax 3) from A5J5. Connect a test cable from A5J5 to the input of an HP 8566A/B.

IF Section 9-17