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(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)At those frequencies indicated in Table
0 Hz (DC)
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 1V 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
20 log10 | 2FM2 | |||
| ||||
FM1 | ||||
|
External FM frequency response (ALC on)
Test procedure
(1)Connect the test equipment as shown in Fig.
(2)On the UUT set:
Carr Freq | 15 MHz |
RF Level | 0 dBm |
Mod Mode | FM External |
FM1 Level | 10 kHz |
Source On |
|
Mod On |
|
ALC coupling |
|
(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)Set the function generator to 1.25 V RMS and repeat (4) to (6) using Table