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3-13 FREQUENCY
MODULATION TESTS
This procedure verifies the operation of the 682XXB/683XXB fre
-
quency modulation input sensitivity circuitry.
The RF OUTPUT of the 682XXB/683XXB is monitored on a Spectrum
Analyzer display. In Unlocked Wide FM mode, the Spectrum Analyzer
is used as a frequency counter to measure the actual FM deviation and
determine FM accuracy. In Unlocked Narrow, Locked, and Locked
Low-Noise FM modes, the Spectrum Analyzer is used to monitor the
carrier level. FM accuracy is determined by measuring the actual FM
deviation necessary to reduce the carrier level to its lowest level.
These tests qualify how the FM input signal affects the signal genera
-
tor’s RF output.
Test Setup
Connect the equipment, shown in Figure 3-8, as fol
-
lows:
1. Connect the 682XXB/683XXB rear panel 10 MHz
REF OUT to the Spectrum Analyzer External Ref
-
erence Input.
2. Connect the RF OUTPUT of the 682XXB/683XXB
to the Spectrum Analyzer RF Input.
FM Input
Sensitivity
Procedure
The following procedure lets you measure the FM
deviation for a specific input sensitivity in Unlocked
Wide, Unlocked Narrow, Locked, and Locked Low-
Noise FM modes and determine FM accuracy.
682XXB/683XXB MM 3-33
10 MHz
REF OUT
682XXB / 683XXB
EXT REF
INPUT
RF OUT
Spectrum Analyzer
RF IN
Figure 3-8. Equipment Setup for Frequency Modulation Tests
PERFORMANCE FREQUENCY
VERIFICATION MODULATION TESTS