ACCEPTANCE TESTING
6-13
External modulation
Specification
With ALC off, the modulation is calibrated for an input level of 1.0 V
PD RMS
With ALC on, the modulation is calibrated for input levels between
0.7 V and 1.4 V PD RMS
Distortion:
Additional 0.1% from 50 Hz to 20 kHz at 1 V RMS with ALC on
Flatness:
Typical 1 dB bandwidth, 10 Hz to 500 kHz
Test equipment
Description Minimum
specification Example
Function generator
10 Hz to 500 kHz sine wave ±0.6 dB flatness
HP 3325B
Digital multimeter
10 Hz to 500 kHz
Datron 1061A
Audio analyzer
Capable of measuring THD down to 0.03% from
50 Hz to 20 kHz
Rohde & Schwarz
UPA3
Mod ALC on flatness
Test procedures
C0221
UUT
Digital Multimeter
INPUT
50
Ω
Load
EXT MOD 1
INPUT
LF
OUTPUT
➤
➤
Function Generator
OUTPUT
Fig. 6-7 External modulation test set-up
Mod input 1
(1) Connect the test equipment as shown in Fig. 6-7.
(2) Set the function generator to 1 V RMS sine wave output at a frequency of 1 kHz.
(3) Set the UUT to EXT MOD 1 INPUT with ALC ON as follows:
[LF]
[Mod Drive]
[SIG GEN]
[FM]
90 kHz
[Select Source]
[Select External]
[Ext1 ALC Coupling]
[SIG GEN]
(4) Set the digital multimeter to read dB and measure and record this value.
(5) Set the function generator to the frequencies given in Table 6-9 and measure the LF output
relative to that reading taken in (4) above. The difference should be less than 1 dB.
(6) Set the function generator to give 0.7 V output and repeat (4) and (5) above.
(7) Set the function generator to give 1.4 V output and repeat (4) and (5) above.