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Line 1: '''Difference in the Depth of Modulation''' or '''DDM''' is a method used by the [[Instrument Landing System]] in conjunction with the associated airborne receiving equipment to define a position in airspace.<ref>[http://stinet.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA138301 Evaluation of Instrument Landing System DDM (Difference in Depth of Modulation) Calibration Accuracies<!-- Bot generated title -->]</ref> DDM is usually expressed in percentage, however may also be expressed in microAmperes. Instrument Landing system ground stations provide [[radio frequency]] signals that vary linearly in the depth of [[modulation]] from the centre or Course Line at a rate of 0.00145% per metre. The two individual audio modulation frequencies and their associated sidebands are 150[[Hertz\|Hz]] and 90Hz. ==Method==

Difference in the depth of modulation: Difference between revisions