ACCEPTANCE TESTING
7-20
External FM frequency response (ALC off, DC coupled)
Test procedure
UUT
50
load
MOD I/O
RF
OUTPUT
OUTPUT
Temporary
connection
C4671
Function
Generator
Audio
Analyzer
DVM
2305
Modulation Meter
RF
INPUT
LF
OUTPUT
INPUT
Fig. 7-9 External modulation and modulation distortion test set-up
30 Hz to 100 kHz
(1)
Connect the test equipment as shown in Fig. 7-9.
(2)
On the UUT set source A to:
[Carr Freq]
15
[MHz]
[RF Level]
0
[dB]
[FM
Devn]
100
[kHz]
[FM
ON/OFF]
[UTIL]
[Mod’n
Mode]
Press
[Down]
until “FM external” can be selected
[Select Mode] [EXIT]
[SIG
GEN]
[Select Coupling] [Ext DC Coupling] [DCFM Nulling] [EXIT]
(3)
Set the function generator to give 1 V RMS, 1 kHz sine wave.
(4)
On the modulation meter, select CAL, FM, 10 Hz
Þ
300 kHz filter.
(5)
On the modulation meter, check that the FM reading is between 47.5 kHz and 52.5 kHz,
then set a reference using the relative function.
(6) Set the function generator to each of the frequencies shown in
Table 7-31
checking that the
relative readings on the modulation meter are within specification.
(7) At those frequencies indicated in
Table 7-31
, set the modulation meter LF output control to
mid-position and measure the AF distortion on the audio analyzer, checking that the results
are within specification.
