Depth Of Modulation (Dom); Fm Demodulation - Deviser S7200 User Manual

Part II: Settings and Measurements
4-7

Depth of Modulation (DOM)

From the Channel Measurement mode, tap DOM to start the Depth of Modulation function. Depth of
modulation is measured as the percentage of the total amplitude change of the carrier, as the signal
progresses from sync tip to peak white.
4-8

FM Demodulation

From the Channel Measurement mode, tap FM DEMOD to listen to FM audio broadcast / analog TV audio.
FM Frequency Demodulation, Loop Count = 1
4-8.1 Settings
Channel: The channel to measure. Select any analog TV/FM channel in the active channel plan.
Frequency: Input range 4-1220 MHz.
Loop Count: Input range 1-100. If >1, the signal deviation trace appears, refreshing every 20 loops.
Button Operation
Listen: Activates audio playback of the FM signal. Tap Vol+ or Vol- to adjust the volume.
Test Results
Level: Displays the level of the current analog signal.
FM Deviation: Signal deviation. See lower green bar. Disabled when Listen mode is on.
FM Max Deviation: Displays the maximum recorded FM Dev in the current session. See lower red bar.
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You can measure depth of modulation on a TV
channel with a vertical interval test signal (VITS). A test
signal transmitted on the VITS of program video
provides a reference to calibrate the video depth of
modulation.
Transmission standards require that the DOM ratio be in
the range of 87.5%. At horizontal sync position, the
carrier reaches maximum amplitude. At the peak
white color position, the carrier amplitude is 12.5% less
than the maximum amplitude.
FM Frequency Demodulation, Loop Count > 1