ACCEPTANCE TESTING
6-17
External AM
Specification
Accuracy:
With ALC OFF the modulation is calibrated for an input level of
1.0 V PD RMS sine wave.
Bandwidth:
±
1 dB, DC to 30 kHz relative to 1 kHz
Typically
±
1 dB DC to 50 kHz, relative to 1 kHz.
Test equipment
Description Minimum
specification Example
Modulation meter
Modulation frequencies from 30 Hz to 50 kHz.
Aeroflex 2305
Function generator
DC to 50 kHz.
HP3325B
Power meter
Capable of measuring levels at 400 MHz.
Aeroflex 6960B
and 6912 sensor
Test procedures
C0433
UUT
50
Ω
Load
EXT MOD 1
INPUT
RF
OUTPUT
➤
➤
Function Generator
OUTPUT
➤
Modulation Meter
RF
INPUT
Fig. 6-10 External AM test set-up
(1) Connect the test equipment as shown in Fig. 6-10.
(2) Set the UUT to
[RF Level]
+7 dBm (+4 dBm for instruments fitted with Option 012)
[Carrier
Freq.]
400 MHz
[AM]
80%. Then select EXT MOD 1 INPUT, DC coupled as follows:
[Select Source]
[Select External]
[Ext1 DC Coupling]
[SIG GEN]
(3) Set the function generator to give 1 V RMS at 1 kHz sine wave.
(4) With the modulation meter set to measure AM, set a reference using the relative function.
(5) Set the function generator to the frequencies shown in Table 6-12 and measure the change in
external AM response which should be less than 1 dB with respect to 1 kHz.
Table 6-12 External AM test frequencies
Modulation frequency
100 Hz
1 kHz
30 kHz
300 Hz
10 kHz
50 kHz