Chapter 3 143
Manual Adjustment Procedures
9. Demodulator Adjustment
Equipment
AM/FM signal generator ...................................................8640B
Oscilloscope ......................................................................54501A
Adapters
Type N (m) to BNC (f) (2 required) ............................ 1250-1476
Type N (f) to 2.4 mm (f) ...................................................11903B
Cables
BNC, 122 cm (48 in) ........................................................10503A
Oscilloscope probe ...........................................................10432A
Procedure
1. Press LINE to turn the spectrum analyzer off. Place the spectrum
analyzer in the service position as illustrated in Figure 3-18 on page
142.
2. Connect the oscilloscope probe from the oscilloscope channel 1 input
to probe A4C723 (the end closest to A4U707) as in Figure 3-19 on
page 144. Press
LINE to turn the spectrum analyzer on. Connect the
8640B RF OUTPUT to the spectrum analyzer INPUT 50Ω .
3. Set the 8640B controls as follows:
Range MHz .............................................................. 61to128
Frequency ............................................................100.000MHz
Output level ......................................................................−10dBm
RF .......................................................................................ON
AM ....................................................................................OFF
FM .................................................................................... INT
Modulation frequency ...............................................1000Hz
Peak deviation .............................................................. 5kHz
Scale FM ......................................................................(k/MHz)
4. Adjust the 8640B FM deviation vernier for a full-scale reading on
the meter. Set the FM to off.
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