Anritsu MG3641A - Manual (Page 94)

SECTION 5 MEASUREMENT
5.1.1 Measuring 20 dB NQ sensitivity
The 20 dB NQ sensitivity is indicated the carrier input voltage (reading value of the output voltage of the signal
generator) required to suppress the noise output by 20 dB when there is no 20 dB noise quieting, e.g., signal input.
To obtain the noise output before suppressed, adjust the volume adjustment volume of the receiver so that the rated
signal output is obtained.
(1) Setup
Fig. 5-1. Measuring 20 dB NQ Sensitivity
(2) Measurement procedure
STEP PROCEDURE
1. Set the MG3641A/MG3642A frequency to 154.45 MHz.
2. Set the MG3641A/MG3642A frequency deviation to 70 % (3.5 kHz for maximum frequency deviation 5
kHz) of the specified maximum frequency deviation. Then, set the internal modulation frequency to 1 kHz.
3. Set the MG3641A/MG3642A to a sufficiently high output (ordinarily 30 dB
µ or more) and apply it to the
receiver.
4. Turn off the squelch of the receiver, synchronize the receiver with receiving frequency 154.45 MHz (so that
the reading value of the level meter is the maximum), then adjust the volume adjust volume of the receiver
so that the rated output of the receiver is obtained according to the indicator of the level meter.
5. Turn off the MG3641A/MG3642A output.
6. Use the level meter to measure the receiver noise output and set the meter indicator to 0 dB.
7. Turn off the MG3641A/MG3642A modulation and turn on the MG3641A/MG3642A output.
8. Adjust the MG3641A/MG3642A output level so that the indicator of the level meter is set to –20 dB.
9. The reading value of the MG3641A/MG3642A output level indicator is a 20 dB NQ sensitivity in step 8.
MG3641A/MG3642A
DA FM RX DL LM
(154.45MHz)
Pseudo-
antenna
FM
receiver
Standard
pseudo-load
Level
meter