1、2021/6/71 AVIONICS FUNDAMENTALS VERY HIGH FREQUENCY OMNI RANGE 2021/6/72 VOR Very High Frequency Omni Range 2021/6/73 Purpose of a VOR System VOR is an enroute, station-to-station Radio Navigation System Provides Heading and Bearing information Used to create “Airways” Assists in providing “Position

2、 Fix” Auto-tunes DME when a VOR frequency is selected 2021/6/74 2021/6/75 Components of a VOR System Antenna Receiver Control Head Indication Interconnecting wiring and antenna coaxial cable 2021/6/76 Large Aircraft VOR Systems The NAV receiver is typically located in the radio rack or avionics comp

3、artment 2021/6/77 Frequency Selector Larger aircraft have a remote mounted frequency selector in the cockpit. Often a combined NAV/COM frequency selector Usually mounted on the glareshield or pedestal 2021/6/78 2021/6/79 Light Aircraft NAV Control Head Smaller aircraft employ a panel mounted receive

4、r Frequency selection is on the front of the receiver 2021/6/710 2021/6/711 VOR Antennas 2021/6/712 VOR Indications VOR indications can be displayed on a variety of different instruments. “Manual” VOR indications are displayed on “Course Deviation Indicator” type instruments 2021/6/713 Manual VOR CD

5、I Indicators 2021/6/714 Horizontal Situation Indicator (H.S.I.) Each “dot” of deviation represents 5 degrees. 2021/6/715 VOR Indications “Automatic” VOR indications are displayed on Compass Instruments 2021/6/716 Radio Magnetic Indicator (RMI) 2021/6/717 TO/FROM INDICATION The TO/From indication wil

6、l tell you what the aircraft would do, IF you were to turn onto the selected course heading. 2021/6/718 VOR Theory of Operation The VOR system operates in the VHF frequency band , from 108.0 to 117.95 MHz. NON LOCALIZER FREQUENCIES 2021/6/719 VOR Ground Station 2021/6/720 VOR uses 2 types of modulat

7、ion A 30 HZ FM Reference Signal A 30 HZ AM Variable Signal The VOR receiver compares the PHASE difference between the two signals 2021/6/721 FM Reference Signal A 30 HZ, FM “Sub carrier” is transmitted omnidirectional at (9960 HZ, +/- 480 HZ) The “Sub carrier” is applied as Amplitude Modulation (AM)

8、 to the R.F. 2021/6/722 30 HZ Variable Signal The R.F. carrier wave (108-118 MHZ) is electronically rotated during transmission, at a speed of 1800 RPM Or 30 Cycles Per Second (HZ) 2021/6/723 Synchronizing the FM and AM The FM Reference signal is synchronized with the rotating directional (AM) signa

9、l The FM Reference will always be at its positive peak when the directional (AM) signal is pointed NORTH 2021/6/724 Synchronizing the FM and AM VOR receivers will detect the AM signals positive peak, when the directional signal is pointed at the aircraft 2021/6/725 Synchronizing the FM and AM The 30

10、 HZ FM Reference will be “IN PHASE” With the 30 HZ Variable if the aircraft is directly NORTH of the VOR transmitter The phase difference between the 30 HZ FM Reference, and the 30 HZ AM Variable will represent the bearing from the station 2021/6/726 Resolving the Phase Difference The phase difference is resolved by the OBS in the