HP 8920A - To Make an FM Hum and Noise Measurement

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Chapter 6, Call Processing Subsystem
Using the ANALOG MEAS Screen
To Make an FM Hum and Noise Measurement
1. If not already done, condition the Test Set. See "Conditioning the Test Set for Call
Processing" on page 141 for further information.
2. If not already done, configure the Test Set. See "Configure the Test Set" on page 142
for further information.
3. Connect the mobile station to the Test Set as shown in Figure 17, "Connecting a
Mobile Station to the Test Set," on page 119.
NOTE: The mobile station’s speaker output must be connected to the Test Set’s AUDIO IN and the
mobile station’s microphone input must be connected to the Test Set’s AUDIO OUT in order
to use the ANALOG MEAS screen.
4. Turn on the mobile station.
Ensure that the Test Set is in the connected state. See "Page a Mobile Station" on page
145 for information on how to bring a mobile station up on a voice channel.
5. If the ANALOG MEAS screen is not displayed, select the ANLG MEAS field from the
To Screen menu. The ANALOG MEAS screen will be displayed.
NOTE: It is recommended that the mobile station’s microphone be muted, if possible, when making
measurements on the mobile stations RF carrier. If the microphone is not muted it is possible
for extraneous noise to be picked up by the microphone and adversely affect the
measurements.
6. The following example illustrates how to make a FM Hum and Noise measurement:
a. Select the Amplitude field and set it to −47 dBm.
b. Select the AFGen1 Freq field and set it to 1 kHz.
c. Select the upper AFGen1 To field and set it to Audio Out.
d. Select the AF Anl In field and select FM Demod.
e. Select the Filter 1 field and select C MESSAGE.
f. Select the Filter 2 field and select >99kHz LP.
g. Position the cursor on the De-Emphasis field and select 750 us.
h. Select the Detector field and select PK+.
i. Select the measurement field and select AF Freq.
j. Select the lower AFGen1 To field and adjust the signal level until the FM Devi-
ation field on the upper portion of the CRT reads 8 kHz.
k. Select the Detector field and select RMS.
l. Select the FM Deviation field.
m. Press the blue SHIFT key, the INCR -10 key, then the ENTER key. This sets a zero
reference point.
n. Select the lower AFGen1 To field and press the ON/OFF key. This turns off the
modulating signal to the mobile station transmitter.
o. The FM Hum and Noise figure is displayed in the FM Deviation field.