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At what Frequency operate TCAS
Билет № 22
1). Cycle - The interval between any two points that measures the completion of a single wave movement.
2). Amplitude modulation (AM)- is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength (amplitude) of the transmitted signal in relation to the information being sent. For example, changes in signal strength may be used to specify the sounds to be reproduced by a loudspeaker, or the light intensity of television pixels. This contrasts with frequency modulation, in which the frequency of the carrier signal is varied, and phase modulation, in which the phase is varied, by the modulating signal.
3). At what Frequency operate NDB. These facilities normally operate in a frequency band of 190 to 535 kilohertz (kHz), according to ICAO Annex 10 the frequency range for NDBs is between 190 and 1750 kHz, and transmit a continuous carrier with either 400 or 1020 hertz (Hz) modulation. All radio beacons except the compass locators transmit a continuous three-letter identification in code except during voice transmissions.
Билет № 23
1). Hertz - Hertz (abbreviated: Hz) is the standard unit of measurement used for measuring frequency. Since frequency is measured in cycles per second, one hertz equals one cycle per second.
2). Frequency modulation (FM)- is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. In analog signal applications, the difference between the instantaneous and the base frequency of the carrier is directly proportional to the instantaneous value of the input-signal amplitude.
Frequency modulation uses the information signal, to vary the carrier frequency within some small range about its original value.
3). At what Frequency operate VOR - VORs operate within the 108.0 to 117.95 MHz frequency band and have a power output necessary to provide coverage within their assigned operational service volume. They are subject to line-of-sight restrictions, and the range varies proportionally to the altitude of the receiving equipment.
Билет № 24
1). Keying - refers to the modulation. Modulation is the process of impressing intelligence upon such a wave. Carrier waves may be changed to transmit information in the following ways: Keying consists of starting and stopping the continuous carrier wave so as to break it up in the form of dots and dashes. A radio navigation facility may break its carrier to identify itself by means of dots and dashes.
2). Describe the term Polar Diagrams-a diagram in which a point of origin is surrounded by a curve whose radius at any given point is proportional to the magnitude of some property measured in the direction of that point.
3). At what Frequency operate GNSS-by frequency we have receivers that operate with navigation signals in more than just the standard upper L-band from about 1560–1610 MHz where we find GPS L1, Galileo E1, Compass B1, and GLONASS L1. The obvious additional frequency is the lower L-band, from about 1170 to 1300 MHz, where again the same four constellations have signals.
Билет № 25
1). Amplitude- the strength or width of one wave the greater the distance from the transmitting site, the smaller this distance.
2). Describe the term Pulse modulation-pulse modulation a type of modulation in which a train of pulses is used as the carrier wave, one or more of its parameters, such as amplitude, being modulated or modified in order to carry information.
3). At what Frequency operate DME - operating frequency range of a DME according to ICAO Annex 10 is from 960 MHz to 1215 MHz. Aircraft equipped with TACAN equipment will receive distance information from a VORTAC automatically, while aircraft equipped with VOR must have a separate DME airborne unit.
Билет №26
1). Frequency - the number of cycles per second, expressed in three units—Kilohertz (KHz), which measures the number of cycles per second, Megahertz (MHz), which measures millions of cycles per second, and Gigahertz (GHz), which measure billions of cycles per second.
2). Sidebands - In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process. The sidebands consist of all the Fourier components of the modulated signal except the carrier. All forms of modulation produce sidebands.
At what Frequency operate TCAS
TCAS involves communication between all aircraft equipped with an appropriate transponder (provided the transponder is enabled and set up properly). Each TCAS-equipped aircraft interrogates all other aircraft in a determined range about their position (via the 1,030 MHz radio frequency), and all other aircraft reply to other interrogations (via 1,090 MHz). This interrogation-and-response cycle may occur several times per second.
Билет №27
1). Wavelength. The distance travelled by a radio wave in one complete cycle.
2). Refraction. When a radio wave travels obliquely from a medium of one density to another of different density, it is bent or refracted at the surface separating the two media. The refraction occurs because radio waves travel at slightly different velocities in different media. Thus at the interface between the media there is a slight change of wavelength.
The following are well-known examples of refraction:
· COASTAL REFRACTION where there is a change of direction when the radio wave crosses the coast. This is due to the different levels of attenuation and the different speed of radio waves over land and water.
· ATMOSPHERIC REFRACTION where changes in direction occur due to variations in temperature, pressure and humidity, particularly at low altitude. Normal levels of atmospheric attenuations cause the radio horizon to be different to the visual horizon.
· IONOSPHERIC REFRACTION where changes in direction occur when the radio wave passes through the ionized layers of the earth’s upper atmosphere.
3). At what Frequency operate Loran C- is acronym for ‘’Long range navigation”. LORAN C is a hyperbolic system operating at a frequency of 100 kHz. In uses the principle of differential range by pulse technique to measure the time difference between the arrival, at an aircraft’s receiver, of a series of pulses from a Master transmitter and a series of pulses from up to four Slave or Secondary transmitters; this arrangement of transmitters is known as a chain. Loran C is also used as a non-precision approach aid in the USA.
Loran C was planned to be shut down by the end of year 2000 but has now been extended until the end of 2008, and it is very likely that it will be extended for several more years beyond 2008.
Билет №28
1). Wavelength-Frequency Relationship.For a transmission of frequency of 1 Hz, a wave will travel a distance of 300 000kilometres.The relationship between frequencies, wavelength and the speed of radio waves is as follows:
WAVELENGTH = SPEED OF RADIO WAVES/FREQUENCY
FREQUENCY=SPEED OF RADIO WAVES/WAVELENGTH
2). Reflection. The term so used when a radio waves bounces off a solid surface, Reflection from targets causes radar pulses to return to the aerial from which they were transmitted but in some circumstances, there are adverse effects of reflection. The direct and ground reflected waves have followed different paths and are therefore likely to arrive at the receiving aerial out of phase. This can cause fading of temporary loss of signals.
3). Frequency operate ILS.Instrument Landing system is a runway approach aid providing lateral (localizer) and vertical (glideslope) guidance that allows aircraft to safely approach the runway from several miles out.
Localizers transmit in the VHF band on frequencies between 108 and 112 MHz. This range of frequencies is shared with VOR so only the odd tenths (plus 50 kHz) are available for ILS. Typicals localizer frequencies are 108.10, 108.15, 108.30 etc.
Glide Slope transmissions are in the UHF band on frequencies between 329 and335 MHz.
Билет №29