Radio Navigation Flashcards
(44 cards)
Cycle
Interval between any 2 points measuring the completion of a single wave movement
Diffraction
Bending which occurs when a wave grazes the edge of a solid object through which it cannot pass
Attenuation
- Loss of wave as it travels through a medium
- Example is driving away from a radio station
Ionosphere
- Layer of rarified ionized gas believed to be caused by ultra-violet solar radiation
- Ranges from 60 to 200 miles above the earth and vary according to time of day, season, and latitude
Ground Waves
- Parts of the transmitted radiation that follows the surface of the earth
- Not subject to ionospheric interference or weather
- Suffers from surface attenuation proportional to the frequency
- Lower frequencies = less attenuation
Space Waves
Parts of the transmitted radiation that travel directly into space
Sky Waves
- Parts of the transmitted radiation that is reflected or refracted from the ionosphere
- Continues to reflect between the earth and sky until completely attenuated
- Skip Zone
- The distance between the end of the useful ground wave and the point where the sky wave is returned to earth
Ground Waves Radio Frequency Categories
- Very Low Frequency (VLF)
- Low Frequency (LF)
- Medium Frequency (MF)
Sky Waves Radio Frequency Categories
High Frequency (HF)
Space Waves Radio Frequency Categories
- Very High Frequency (VHF)
- Ultra High Frequency (UHF)
- Super High Frequency (SHF)
- Extremely High Frequency (EHF)
- Line of sigh transmission
- Signals not affected by time of day, season, precipitation, or atmospheric conditions
Characteristics of VHF Signals
- Do not follow the curvature of the earth
- Do not bend around obstructions
- Primarily space waves
- Reception is limited by line of sight
VHF Omnidirectional Range (VOR)
- Frequency Range is 108.1-117.95 MHz (VHF)
- 3 letter morse code identifier
- Transmits 2 signals, a reference phase and variable phase
- Beacon rotates at 6 RPM, green light flashes the instant the beacon passes magnetic north
- Actual VOR does this electronically
- Beams emitted by VOR called radials
VOR components - Omni Bearing Selector (OBS)
Selects Desired Radial
VOR components - Course Deviation Indicator (CDI)
- Shows aircraft position relative to selected radial
- Each dots equals 2 degrees up to a maximum of 10 degrees either side of radial
VOR components - Sense Indicator (TO/FROM)
Indicates whether the aircraft is the TO or FROM side of the VOR
VOR interpretation
- VOR interpretations are dependant only on the position relative to the selected radial
- Rule of thumb is that in order to properly navigate, the heading and the OBS must agree or else reverse sensing will occur
VOR Homing (Direct to VOR site)
- Tune to proper frequency
- Confirm proper morse code using IDENT
- Rotate OBS knob to obtain a TO indication
- Rotate the OBS until the CDI centers with a TO indication
- Fly the heading under the OBS indicator
- Adjust heading as needed to keep CDI centered
VOR Position Fixing (Finding exact location using 2 VOR’s)
- Tune and Identify VOR-A
- Centre the needle with a FROM indication, OBS is radial the aircraft is on
- Draw a line on map from centre of VOR compass rose out through the indicated radial
- Repeat for VOR-B
- Aircraft’s position is where lines intersect
VOR Serviceability Checks - VOR Test Facility (VOT)
- Sends out one radial, 360º
- CDI centres 360º FROM and 180º TO
- CDI must centre within 4º
VOR Serviceability Checks - VOR Check Point
CDI must centre within 4º
VOR Serviceability Checks - Dual VOR
- Same radial on two VOR’s
- CDI must agree within 4º
VOR Serviceability Checks - Airborne VOR Check
Over a known fix or landcmark CDI must agree within 6º
VOR Facilities
- Stand Alone VOR is radial information only
- VOR and co-located DME
- TACAN is similar to a VOR but uses UHF frequencies and is for military use, always has DME
- Often a TACAN is co-located with a VOR and is called a VORTAC
Automatic Direction Finder (ADF)
- Frequency Range between 190 and 415 kHz and 510-535 kHz (LF/MF)
- 1,2, or 3 letter Morse code identifier
- Transmits a single non-directional signal
- Mostly ground waves and some sky waves
- Follows curvature of the earth
- Reception is greater than VHF at low altitudes and over longer distances