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1、AVIONICS FUNDAMENTALSVERY HIGH FREQUENCY OMNI RANGE1VORVery High Frequency Omni Range2Purpose of a VOR SystemVOR is an enroute, station-to-station Radio Navigation SystemProvides Heading and Bearing informationUsed to create “Airways”Assists in providing “Position Fix”Auto-tunes DME when a VOR frequ
2、ency is selected34Components of a VOR SystemAntennaReceiverControl HeadIndicationInterconnecting wiring and antenna coaxial cable5Large Aircraft VOR SystemsThe NAV receiver is typically located in the radio rack or avionics compartment6Frequency SelectorLarger aircraft have a remote mounted frequenc
3、y selector in the cockpit.Often a combined NAV/COM frequency selectorUsually mounted on the glareshield or pedestal78Light Aircraft NAV Control HeadSmaller aircraft employ a panel mounted receiverFrequency selection is on the front of the receiver910VOR Antennas11VOR IndicationsVOR indications can b
4、e displayed on a variety of different instruments.“Manual” VOR indications are displayed on “Course Deviation Indicator”type instruments12Manual VOR CDI Indicators13Horizontal Situation Indicator(H.S.I.)Each “dot” of deviation represents 5 degrees.14VOR Indications“Automatic” VOR indications are dis
5、played onCompass Instruments15Radio Magnetic Indicator(RMI)16TO/FROM INDICATIONThe TO/From indication will tell you what the aircraft would do, IF you were to turn onto the selected course heading.17VOR Theory of OperationThe VOR system operates in the VHF frequency band , from 108.0 to 117.95 MHz.
6、NON LOCALIZER FREQUENCIES18VOR Ground Station19VOR uses 2 types of modulationA 30 HZ FM Reference SignalA 30 HZ AM Variable SignalThe VOR receiver compares the PHASE difference between the two signals20FM Reference SignalA 30 HZ, FM “Sub carrier” is transmitted omnidirectional at (9960 HZ, +/- 480 H
7、Z)The “Sub carrier” is applied as Amplitude Modulation (AM) to the R.F.2130 HZ Variable SignalThe R.F. carrier wave (108-118 MHZ) is electronically rotated during transmission, at a speed of 1800 RPMOr30 Cycles Per Second(HZ)22Synchronizing the FM and AMThe FM Reference signal is synchronized with t
8、he rotating directional (AM) signalThe FM Reference will always be at its positive peak when the directional (AM) signal is pointed NORTH23Synchronizing the FM and AMVOR receivers will detect the AM signals positive peak, when the directional signal is pointed at the aircraft24Synchronizing the FM a
9、nd AMThe 30 HZ FM Reference will be “IN PHASE”With the 30 HZ Variable if the aircraft is directly NORTH of the VOR transmitterThe phase difference between the 30 HZ FM Reference, and the 30 HZ AM Variable will represent the bearing from the station25Resolving the Phase DifferenceThe phase difference is resolved by the OBS in the CDI during manual VOR operationsThe phase difference is resolved by the compass card during automatic VOR operations2627
