Frequency Counter Prescaler/Conditioner; Am/Fm Demodulator - Agilent Technologies 8564EC Service Manual

IF Section
Log Amplifier (P/O A4 Assembly)
4. Set the oscilloscope controls as follows:
Amplitude scale ................................................... 200 mV/div
Offset ........................................................................ +400 mV
Coupling ............................................................................... dc
Sweep time ....................................................... 50 µs/division
5. The oscilloscope should display a 4.8 kHz sine wave.
6. Disconnect the cable from the CAL OUTPUT and the INPUT 50Ω
connectors.
7. Set the resolution bandwidth to 2 MHz.
8. Broadband noise should be displayed on the oscilloscope from
approximately +200 mV to +400 mV.
is decreased in 10 dB steps from −10 dBm to
9. As the
REF LVL
−70 dBm, the noise displayed on the oscilloscope should increase in
100 mV increments. If this response is not observed, refer to
Gains" and "Video
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 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 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.
448
Offset".
"Step
Chapter 9