Residual Am Test - Wavetek 3000 Instruction Manual

PERFORMANCE TESTS
4 .8
RESIDUAL AM TEST
SPECIFICATION
>65 dB below carrier in a 50 Hz to 15 kHz post-detection
bandwidth .
METHOD
EQUIPMENT
Modulation Meter Radiometer AFM2
Distortion Analyzer HP334A
A modulation meter
operating in AM mode is used to demodu-
late the Signal Generator output at the
minimum leveler
point where AM noise is maximum .
A distortion analyzer (oper-
ating in level mode)
is used to increase the resolution of
the demodulated output of the modulation meter . The system
is calibrated at a 10% AM level . The 10% AM is removed and
the residual AM is read in dB below the calibrated 10% AM
level . 20 dB is added to the reading to relate the residual
AM to the carrier .
PROCEDURE
1 . Set the Signal Generator controls as follows :
FREQUENCY selector
500 .000 MHz
MODULATION MODE AM
MODULATION FREQ 1 kHz
MODULATION FM/AM 0% AM
OUTPUT VERNIER
-7 dBm reading on OUTPUT meter
OUTPUT step attenuator
0 dBm
Figure 4-2 .
Residual AM Setup
3 .
Set the modulation meter to read %AM at 500 MHz . Set
the RF input attenuation to 10 dB, the IF bandwidth to ±400
kHz, the meter response to fast, the function switch to +AM,
the meter range switch to 10 and the filter bandwidth to 50
Hz-15 kHz .
2 .
Connect the equipment as shown in Figure 4-2 .
Model 3000
Signal Generator
Modulation Meter
Distortion Analyzer
Input
RF
AF O
RF Out
Input
OutDut