ACCEPTANCE TESTING
7-21
0 Hz (DC)
Note than to measure the FM deviation at DC, it will be necessary to use the DC offset facility on
the function generator proceeding as follows:
(8)
Set the function generator to +1.4142 V DC (temporarily connect the function generator
output to the DVM and set this voltage as close as possible to +1.4142 V).
(9)
Press CARRIER ERROR on the modulation meter.
(10) Set the function generator to
−
1.4142 V DC (temporarily connect the function generator
output to the DVM and set this voltage as close as possible to
−
1.4142 V).
(11) Measure the frequency indicated on the modulation meter carrier frequency window.
FM1 _____
(12) Reset the function generator to 1 V RMS, 1 kHz sine wave and measure the FM deviation.
FM2 _____
(13) Using the following formula, calculate the change in response checking that the result is
within the specification shown against 0 Hz in
Table 7-31
.
20log
10
2FM2
FM1
(14) Repeat (2) to (13) for source B.
External FM frequency response (ALC on)
Test procedure
(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 ALC Coupling] [EXIT]
(3)
Set the function generator to give 0.75 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 9.5 kHz and 10.5 kHz, then
set a reference using the relative function.
(6) Set the function generator to each of the frequencies shown in
Table 7-32
checking that the
relative readings on the modulation meter are within specification.
(7) Set the function generator to 1.25 V RMS and repeat (4) to (6) using
Table 7-33
, also
measuring the AF distortion on the audio analyzer at those frequencies indicated.
(8)
Repeat (2) to (7) for source B.
