Operating instructions

ACCEPTANCE TESTING
5-12 46882-311D
Frequency modulation
Specification
Carrier range 400 kHz to 1.05 GHz
Accuracy
†
±5% ± 10 Hz at 1 kHz modulating frequency.
± 10% ± 10 Hz for modulating frequencies from 50 Hz to 15 kHz.
Distortion Less than 1% at 1 kHz for deviation of 5 kHz, CCITT Weighted.
† At low modulation levels the residual AM/FM may become significant
Test equipment
Description Minimum specification Example
Modulation meter RF I/P 500 kHz to 1.05 GHz FM Measurement
accuracy ±0.5% of reading ±1 least significant
changing digit at 1 kHz mod rate for deviation
>5 kHz
IFR 2305
UUT
C2587
RF INPUT
BNC
OUTPUT
Modulation meter
Fig. 5-9 Internal FM accuracy checks
(1) Refer to Results table 5-15 on page 5-36. Connect the test equipment as shown in Fig. 5-9.
(BNC output on UUT).
(2) Set the UUT to [Rx TEST], RF IN/OUT [SELECT] BNC output, [RF Gen],
[LEVEL] 0 dBm, [FREQ] 0.5 MHz, [Mod Gen], [Gen 2], [LEVEL] 10 kHz, [FREQ] 1 kHz.
All other modulation generators and noise measurements should be switched OFF.
(3) Set the Modulation meter to monitor FM in a 50 Hz to 15 kHz bandwidth, Noise averaging
on.
(4) Check the Modulation meter indicates a reading within
±
5%
±
10 Hz of the deviation set.
Repeat with the UUT set to each of the remaining carrier frequencies shown in the Results
table 5-15.
(5) Refer to Results table 5-16 on page 5-36. Set the UUT to [RF Gen], [FREQ] 600 MHz,
[Mod Gen], [Gen 2], [LEVEL] 75 kHz.
(6) Check the modulation meter indicates a reading within
±
5%
±
10 Hz of the deviation set.
Repeat with the UUT set to provide deviations of 50 kHz, 25 kHz and 5 kHz.
(7) Refer to Results table 5-17 on page 5-36. With the deviation still set at 5 kHz, connect the
LF output of the Modulation meter to the AF input of the UUT. (Set the LF [LEVEL] control
to the brown marker on the Modulation meter.)
(8) Select the 0.3 to 3.4 kHz AF Filter on the UUT and select distortion measurement.
(9) Check that the distortion indicated on the UUT is less than 1%.