Fm Distortion Test - Wavetek 3000 Instruction Manual

4 .16 FM DISTORTION TEST
SPECIFICATION
METHOD
Distortion
<4% (3 to 10 kHz deviation),
-<2% (10 to 500 kHz deviation)
at a frequency of 1 kHz
EQUIPMENT
Modulation Meter Radiometer AFM2
Distortion Analyzer HP334A
8 . Record the larger of the two dB changes obtained in
steps 6 and 7 on line 42 of the PTR .
The measurement is made with a modulation meter and a dis-
tortion analyzer, which measures the distortion of the de-
modulated FM from the modulation meter . Distortion below 3
kHz deviation increases because of residual FM noise .
The
distortion at 3 kHz deviation is measured in an environment
where the noise level <60 dB relative to 2x10 -4 ubar .
PROCEDURE 1 .
Set the Signal Generator controls as follows :
FREQUENCY selector 520 .000 MHz
MODULATION MODE FMxl
MODULATION FREQ 1 kHz
MODULATION FM/AM
3 kHz
OUTPUT VERNIER Fully Clockwise
OUTPUT step attenuator +10 dBm
2 . Connect the equipment as shown in Figure 4-7 .
Figure 4-7 . FM Distortion Setup
PERFORMANCE TESTS
3 . Set the modulation meter to read FM deviation at 520 MHz .
Set the RF input attenuation to 20 dB, the IF bandwidth to
t400 kHz, the meter response to fast, the function switch to
4-25
Model 3000
Signal Generator
Modulation Meter
Distortion Analyzer
Input
RF
AF O
RF Out
IrIput
Output
O