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Video
Output
1. On the HP 85623 spectrum analyzer, press
C-1,
C-1,
300
m,
(SPAN),
100 (Hz),
(m),
-10
dBm,
[WSWP),
a
and IF
BJ
OFF
.
2. Connect the CAL OUTPUT to the INPUT
500
connector.
3. Disconnect W54 (coax 2) from
A4J4.
Connect a short SMB to SMB cable from A4J4 to
an SMB tee and connect W54 to the tee. Connect a test cable from the tee to the input
of an oscilloscope.
4. Set the oscilloscope controls as follows:
Amplitude scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . , 200 mV/div
Offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
+400mV
Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
..~dc
Sweep time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 pus/division
5. The oscilloscope should display a 4.8 kHz sine wave.
6. Disconnect the cable from the CAL OUTPUT and the INPUT
5Ofl
connectors.
7. Set the resolution bandwidth to 2 MHz.
8. Broadband noise should be displayed on the oscilloscope from approximately
i-200
mV
to
t400
mV.
9. As the
REF’
LK, is decreased in 10 dB steps from -10
dBm
to -70
dBm,
the noise
displayed on the oscilloscope should increase in 100
mV
increments. If this response is not
observed, refer to “Step Gains” and “Video Offset” in this chapter.
10. Reconnect cable W54 to A4J4.
Frequency
Counter
Prescaler/Conditioner
Refer to function block Q of A4 Log Amplifier Schematic Diagram (sheet 4 of 4) in the
HP 8560 E-Series Spectrum Analyzer Component Level Information.
The frequency counter
prescaler/conditioner
divides the frequency by two, and then
attenuates it. The circuit consists of frequency divider (U703A) and an output attenuator.
The frequency divider turns on only when the instrument is counting.
AM/FM
Demodulator
Refer to function block R of A4 Log Amplifier Schematic Diagram (sheet 4 of 4) in the
HP 8560 E-Series Spectrum Analyzer Component Level Information.
The demodulator circuitry on the log amplifier on A4 produces a low-level audio signal.
This audio signal is then amplified by the audio amplifier on A4. The FM demodulator
demodulates narrowband FM (5 kHz deviation) signals. The detector (block J) demodulates
AM signals.
1. If demodulation problems occur when the spectrum analyzer is in the frequency domain,
perform the Frequency Span Accuracy performance test and, if necessary, the YTO
Adjustments procedure.
9-16 IF Section