Operating instructions

ACCEPTANCE TESTING
5-19
RF input tests
Modulation analyzer - FM
Specification
Frequency range:
400 kHz to 1.05 GHz
Modulation frequency range:
10 Hz to 15 kHz
Deviation range:
0 to 75 kHz
Resolution:
10 Hz below 2 kHz deviation
1% above 2 kHz deviation
Accuracy (see Note 1)
±5% ± resolution at 1 kHz modulation frequency
Demodulation scope accuracy
±10%
Demodulation output socket
200 mV peak to peak ± 10% per 1 kHz deviation
Demodulation filters
300 Hz LP, 3 kHz LP, 0.3 to 3.4 kHz BP, 15 kHz LP, 750
μs de-emphasis
Residual FM:
Less than 30 Hz (300 Hz to 3.4 kHz)
Note 1:
At low modulation levels, the residual AM/FM may become significant.
Test equipment
Description Minimum specification Example
RF signal generator 5.5 MHz to 1 GHz. Deviation 0 to 75 kHz. Modulation
rate 1 kHz.
IFR 2041
Modulation meter RF I/P 5.5 MHz to 1 GHz. FM measurement accuracy
±0.5% of reading ±1 least significant digit at 1 kHz mod
rate for deviation > 5 kHz.
IFR 2305
Power splitter
6 dB 50 Ω 5.5 MHz to 1 GHz
WEINSCHEL
1870A
DVM 1 % accuracy 1 kHz Solatron 7150+
(1) Refer to Results table 5-21 on page 5-38. Connect the equipment as shown in Fig. 5-13,
connecting the incoming signal to the antenna input socket of the UUT.
(2) Set the Modulation meter to monitor FM in a 50 Hz to 15 kHz bandwidth, noise averaging
on.
(3) Set the UUT to [Tx TEST], RF IN/OUT [SELECT] antenna BNC input socket. From the
power up default, the instrument should already be set to demodulate FM with an IF filter of
30 kHz and AF filter of 0.3 to 3.4 kHz selected. Check that this is the case and select if
necessary.
(4) On the UUT, set [Tx Freq] 5.5 MHz. Set the RF signal generator to provide a signal of
5.5 MHz with 20 kHz deviation at 1 kHz modulation rate. Set the RF level to 6 dBm. (If a
2041 is being used then it should be set to normal noise mode.)