Operating instructions

ACCEPTANCE TESTING
5-10 46882-311D
(12) Refer to Results table 5-9 on page 5-33. Set the UUT to [Rx TEST], RF IN/OUT [SELECT]
BNC output, [RF Gen], [LEVEL] 0 dBm, [ FREQ], 1000 MHz, [Mod Gen], [Gen1/Gen2],
to select modulation generator 2, and then [LEVEL], 1 kHz. After this key sequence
modulation generator 2 should be providing 1 kHz deviation at 1 kHz modulation rate.
Modulation generator 1 should be OFF.
(13) Set the signal generator into low noise mode 1 and to provide a signal of 55.63889 MHz at
0 dBm.
(14) Set the Modulation meter to measure FM in a 300 Hz to 3.4 kHz bandwidth with noise
averaging on. Select external LO by pressing FREQ TUNE, 0, ENTER. External LO should
now appear in the top left of the modulation window display and the frequency window
should display the IF frequency of 1.5 MHz
±
150 kHz. Note the DEVIATION LEVEL (Hz)
displayed on the modulation meter. Set the LF LEVEL control on the front panel of the
modulation meter to the horizontal mark and press HOLD ON/OFF.
(15) Set the DVM to measure AC volts and make a note of the voltage displayed MOD
VOLTAGE (V).
(16) On the UUT press [ON/OFF] to switch modulation generator 2 OFF, then note the
RESIDUAL VOLTAGE (V) displayed on the DVM.
(17) The residual FM in HZ RMS. can now be calculated as follows:-
RESIDUAL FM=
RESIDUAL VOLTAGE
DEVIATION LEVEL
MOD VOLTAGE
×
2
(18) Set the UUT RF Generator and the local oscillator to the frequencies shown in Results
table 5-9, confirming that the residual FM indicated on the Modulation meter is within the
limits shown in the right hand column.
Amplitude modulation
Specification
Carrier range: 400 kHz to 1.05 GHz
Resolution: 1%
Accuracy (up to 85% AM)
Carrier frequency 1.5 to
400 MHz.
±7% of setting ± 1 digit for modulation frequency 1 kHz.
±10% of setting ± 1 digit for modulation frequencies of 50 Hz to 5 kHz.
±15% of setting ±1 digit for modulation frequencies from 50 Hz to
15 kHz.
Distortion: Less than 2% at 1 kHz for modulation depth 30% , CCITT weighted.
Test equipment
Description Minimum specification Example
Modulation meter RF I/P 500 kHz to 400 MHz AM Measurement
accuracy up to 85% depth:- ±1% of reading at
1 kHz mod rate. ±2.5% of reading for mod rates
from 50 Hz to 15 kHz
IFR 2305