TEST PROCEDURES
46882/439 7-19
(6) Set the function generator to each of the frequencies shown in Table 7-33, checking that the
relative readings on the modulation meter are within specification.
(7) At those frequencies indicated in Table 7-33, set the modulation meter LF output control to
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id-position and measure the AF distortion on the audio analyzer, checking that the results
are within specification.
0 Hz (DC)
Note that to measure the FM deviation at DC, it will be necessary to use the DC offset facility on
the function generator. Proceed 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 7-33.
20 log
10
FM2
FM1
(14) Repeat (2) to (13) for source B and, if Option 1 is fitted, source C.
External FM frequency response (ALC on)
Test procedure
(1) Connect the test equipment as shown in Fig. 7-10.
(2) On the UUT set source A to:
[Carrier 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 ⇒ 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 7-34, checking that the
rel
ative 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 7-35, also
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easuring the AF distortion on the audio analyzer at those frequencies indicated.
(8) Repeat (2) to (7) for source B and, if Option 1 is fitted, source C.
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General