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Question 203-1 : In aviation, the reflection on ionosphere layers phenomenon is used in the following frequencies ? [ Exam pilot ]

Hf.

.hf radio communications is dependent for most of its applications on the use of the ionosphere. this region in the atmosphere enables radio communications signals to be reflected, or more correctly refracted back to earth so that they can travel over great distances around the globe. ionospheric propagation is normally though of as an hf propagation mode, although, it use can extend above and below the hf portion of the spectrum on many occasions...once a signal passes through the d region, it travels on and reaches first the e, and next the f regions. at the altitude where these regions are found the air density is very much less, and this means that when the free electrons are excited by radio signals and vibrate, far fewer collisions occur. as a result the way in which these regions act is somewhat different. the electrons are again set in motion by the radio signal, but they tend to re radiate it. as the signal is travelling in an area where the density of electrons is increasing, the further it progresses into the region, the signal is refracted away from the area of higher electron density. in the case of hf signals, this refraction is often sufficient to bend them back to earth. in effect it appears that the region has reflected the signal...the tendency for this reflection is dependent upon the frequency and the angle of incidence. exemple 303 Hf.

Question 203-2 : The wavelength of a radio signal transmitted at the frequency 118.7 mhz is ?

2.53 m.

.wavelength meters = speed of light / frequency..wavelength = 300 000 000 / 118 700 000 = 2.53 m. exemple 307 2.53 m.

Question 203-3 : In the propagation of mf waves, the phenomenon of fading is particularly found ?

At night, due to the combination of the sky and ground waves.

.fading when a receiver picks up the sky signal and the surface signal, the signals will interfere with each other causing the signals to be cancelled out. exemple 311 At night, due to the combination of the sky and ground waves.

Question 203-4 : A radio signal looses strength as range from the transmitter increases, this is called ?

Attenuation.

.attenuation as any radio wave travels away from the transmitter it becomes weaker looses power , or is attenuated. this results from the rf signal inducing currents into the surface of the earth. a good conducting surface, such as water, will give the signal back with little loss of energy. a poor conductive surface, such as a hot desert, will simply absorb the energy. the degree of surface attenuation also varies directly with frequency...there are two main reasons for attenuation. the spreading of available rf energy over a greater area.. rf energy is absorbed by the earth, atmosphere or ionized layers. exemple 315 Attenuation.

Question 203-5 : Skip distance is the ?

Range from the transmitter to the first sky wave.

.skip distance is the distance between the transmitter and the point on the surface of the earth where the first sky return arrives. exemple 319 Range from the transmitter to the first sky wave.

Question 203-6 : The wavelength of a radio transmitted on frequency 121.95 mhz is ?

2.46 m.

.wavelength meters = speed of light / frequency..wavelength = 300 000 000 / 121 950 000 = 2.46 m. exemple 323 2.46 m.

Question 203-7 : What describes polarization ?

Orientation of the plane of oscillation of the electrical component of the electromagnetic wave.

. polarisation electromagnetic radiation is comprised of the e and h fields, which stand for electric and magnetic, respectively..the electric field arises from voltage, and the magnetic on from current. the two act at rightangles to each other.. 2552.a wave's polarisation is noted with reference to the electrical field, so a vertically polarised wave has a vertical electrical field, wich will come from a vertical aerial for efficiency, the receiver must have the same orientation.. 2553.the shape traced out in a fixed plane by the electric vector as such a plane wave passes over it, is a description of the polarization state. the following figures show some examples of the evolution of the electric field vector black , with time the vertical axes , at a particular point in space, along with its x and y components red/left and blue/right , and the path traced by the tip of the vector in the plane purple the same evolution would occur when looking at the electric field at a particular time while evolving the point in space, along the direction opposite to propagation... in linear polarisation the plane of oscillation is fixed in space whereas in circular or eliptical polarisation, the plane is rotating. exemple 327 Orientation of the plane of oscillation of the electrical component of the electromagnetic wave.

Question 203-8 : On which bearings errors caused by the shoreline/coastal effect reach their maximum ?

Bearings 000° 030° degrees to the coastline.

Coastal refraction or shoreline effect.low frequency radio waves will refract or bend near a shoreline, especially if they are close to parallel to it..least when bearings normal to coastline... radio waves passing the coastline at small angles suffer refraction due to different conducting and reflecting properties over land and sea. a false bearing indication is obtained at aircraft flying over sea and taking bearings from ndb located over land. the effect is less for an ndb on coast than one inland and on a bearing 90° to coastline then at an oblique angle. hence, given the choice use beacon at coast and rely on bearings perpendicular to the coastline.. 2554 exemple 331 Bearings 000°-030° degrees to the coastline.

Question 203-9 : The doppler effect onto the radio signals is ?

The shift of frequency of the wave due to the relative movement between the transmitter and the receiver.

exemple 335 The shift of frequency of the wave due to the relative movement between the transmitter and the receiver.

Question 203-10 : The d layer and e layer of the atmosphere are part of the ?

Ionosphere.

. 2551.the ionosphere is the ionized component of the earth's upper atmosphere from 60 to 400 km above the surface, which is vertically structured in three regions or layers d, e and f. exemple 339 Ionosphere.

Question 203-11 : When raising the frequency of an electromagnetic wave. the ?

Wavelength decreases.

.the relationship between wavelength and frequency is.wavelength = speed of light / frequency..if frequency increases, wavelength decreases. exemple 343 Wavelength decreases.

Question 203-12 : The phenomenon when a wave bends when it passes around an impenetrable obstacle is ?

Diffraction.

.diffraction is the phenomenon by which wave energy bends around an object. exemple 347 Diffraction.

Question 203-13 : The phenomenon of a change in direction of an radio wave em wave occurring due to a change in its speed is called ?

Refraction.

.refraction is the process by which a signal's propagation path bends and the signal changes its speed as it moves from one medium to another different density of the mediums. generally the rf energy travels in straight line = following great circle paths. however, in some cases, when there is a change in certain factors the signal's path may change direction. the actual extent of the signal's path change varies significantly with the change of the environment...there are 3 main types of refraction.a coastal = the path of rf signal may change as it crosses a coastline..b atmospheric especially low altitude = changes in the path of rf signal may be caused by the changes in temperature, pressure or humidity..c ionospheric = paths of rf signals may change as they pass through ionized layers. exemple 351 Refraction.

Question 203-14 : A reason that gps satellites use helical antennae is ?

That the signal has a circular polarization.

.helix antennas also commonly called helical antennas have a very distinctive shape, as can be seen in the following picture. 2555.a helical antenna is an antenna consisting of a conducting wire wound in the form of a helix. in most cases, helical antennas are mounted over a ground plane. exemple 355 That the signal has a circular polarization.

Question 203-15 : The mix of an electromagnetic wave with another is called ?

Interference.

.interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude. interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency...this question exists also with this statement superposition of two em waves of the same or nearly the same frequency is called interference. exemple 359 Interference.

Question 203-16 : Speed of a radio wave ?

300 000 km/s.

exemple 363 300 000 km/s.

Question 203-17 : For long range ndb's the most common type is ?

Lf, non a1a.

.non a2a bfo off for a2a idents, 15 w power, 10 25nm range...non a1a bfo on for a1a idents, lf non a1a is used for long range. exemple 367 Lf, non a1a.

Question 203-18 : Mountain effect, occurring for instance with ndbs, is caused by what physical phenomenon ?

Reflection.

.mountain effect mountain areas can cause reflections and, to a lesser extent, diffractions and lead to the error direction reading by adf..this effect, similar to night effect, is obtained in mountainous areas where the energy received from an ndb consists of two or more waves, one of them direct and others by reflection from the mountains. bearing indications are found to change rapidly until the affected area is passed...for information, night effect radio waves take two paths to the radio compass receiver. the first and normal path is along the earth's surface. if only these waves were received, the compass would point directly to the ndb. the second path is via one or more wave refracting layers above the earth the ionosphere returning to earth to mix with direct waves. complete changes in the nature of the waves take place on this path and produce errors in direction. exemple 371 Reflection.

Question 203-19 : Which physical effects affecting wave propagation as shown in the figure. 2556 ?

A = refraction b = absorption c = reflection

exemple 375 A = refraction b = absorption c = reflection

Question 203-20 : Which letter in the figure below indicates the 'skip zone'. 2557 ?

C.

.read carefully skip zone not 'distance'...skip zone dead space is the distance between the limit of the surface wave and the sky wave. exemple 379 C.

Question 203-21 : Which letter in the figure below indicates the 'skip distance'. 2557 ?

D.

.read carefully skip distance not 'zone'...skip distance is the distance between the transmitter and the point on the surface of the earth where the first sky return arrives..it is the range from the transmitter to the first sky wave. exemple 383 D.

Question 203-22 : You are flying over sea parallel to the coastline. an ndb is situated 10 nm inland. in which sectors in the diagram does the shoreline/coastal effect reach its minimum. 2558 ?

Sectors a + b

.coastal refraction or shoreline effect.low frequency radio waves will refract or bend near a shoreline, especially if they are close to parallel to it..least when bearings normal perpendicular to coastline...radio waves passing the coastline at small angles suffer refraction due to different conducting and reflecting properties over land and sea. a false bearing indication is obtained at aircraft flying over sea and taking bearings from ndb located over land. the effect is less for an ndb on coast than one inland and on a bearing 90° to coastline then at an oblique angle. hence, given the choice use beacon at coast and rely on bearings perpendicular to the coastline. exemple 387 Sectors a + b

Question 203-23 : You are flying parallel to the coastline. an ndb is positioned about 10 nm inland. in which areas will you observe the shoreline/coastal effect. 2558 ?

Area c + d, deflection to the coastline.

.coastal refraction or shoreline effect.low frequency radio waves will refract or bend near a shoreline, especially if they are close to parallel to it..least when bearings normal perpendicular to coastline....radio waves passing the coastline at small angles suffer refraction due to different conducting and reflecting properties over land and sea. a false bearing indication is obtained at aircraft flying over sea and taking bearings from ndb located over land. the effect is less for an ndb on coast than one inland and on a bearing 90° to coastline then at an oblique angle. hence, given the choice use beacon at coast and rely on bearings perpendicular to the coastline. exemple 391 Area c + d, deflection to the coastline.

Question 203-24 : The phenomenon of a change in direction of an em wave occurring at an interface between two different media, so that the wave returns into the medium from which it originated, is called ?

Reflection.

Ecqb03, august 2016 exemple 395 Reflection.

Question 203-25 : What is required to enable an antenna to transmit an electromagnetic wave ?

The antenna has to be fed with an alternating current of high frequency.

Ecqb03, august 2016 exemple 399 The antenna has to be fed with an alternating current of high frequency.

Question 203-26 : An electromagnetic wave has two types of energy field ?

An e electrical field and h magnetic field.

.an electromagnetic wave consists of an oscillating electric field e and an oscillating magnetic field h which propagates at the speed of light.. 2552.the e and h fields are perpendicular to each other. exemple 403 An e electrical field and h magnetic field.

Question 203-27 : In aviation electronic systems the so called doppler principle may be used in ?

Vor, gps and mts and the turbulence mode of awr.

.mts multi spectral targeting system. exemple 407 Vor, gps and mts and the turbulence mode of awr.

Question 203-28 : The wavelength of a radio signal transmitted at the frequency of 3 ghz is ?

10 cm.

.wavelength in meter = 300 / frequency in mhz.wavelength in meter = 300 000 / frequency in ghz.wavelength = 300 000 / 3 000 000 = 0.1 m. exemple 411 10 cm.

Question 203-29 : The phase angle of a wave is ?

The fraction of one wavelength expressed in degrees from 000° to 360°.

exemple 415 The fraction of one wavelength expressed in degrees from 000° to 360°.

Question 203-30 : Wavelength is defined as the ?

Physical distance travelled by a radio wave during one cycle of transmission.

. 2549 exemple 419 Physical distance travelled by a radio wave during one cycle of transmission.

Question 203-31 : Antenna...the ils glide path antenna must be located ?

At approximately 300 m after the threshold and approximately 120 m laterally from the runway centreline.

exemple 423 At approximately 300 m after the threshold and approximately 120 m laterally from the runway centreline.

Question 203-32 : The maximum separation distance between a vor and a dme having the same identifier is ?

2000 ft 600 m.

exemple 427 2000 ft (600 m).

Question 203-33 : The ground wave surface wave propagates as follows ?

It travels along the earth' surface and follows the curvature of the earth.

exemple 431 It travels along the earth' surface and follows the curvature of the earth.

Question 203-34 : The sky wave propagates as follows ?

A wave transmitted into space will be reflected back to the earth's surface by the ionosphere.

Ecqb04, november 2017. exemple 435 A wave transmitted into space will be reflected back to the earth's surface by the ionosphere.

Question 203-35 : An electromagnetic waves travelling through the air directly from the transmitter to the receiver, is a ?

Space wave.

Ecqb04, november 2017. exemple 439 Space wave.

Question 203-36 : Radio waves in the vhf and higher frequency bands propagate mainly as ?

Space waves.

Ecqb04, november 2017. exemple 443 Space waves.

Question 203-37 : From which physical phenomenon do sky waves originate ?

Refraction.

exemple 447 Refraction.

Question 203-38 : The skip zone is defined as ?

The area, where neither the ground waves nor the sky waves are received.

Ecqb04, november 2017. exemple 451 The area, where neither the ground waves nor the sky waves are received.

Question 203-39 : The amplitude of an electromagnetic wave is defined as the ?

Maximum deflection in an oscillation or wave.

. 2549.amplitude maximum deflection in an oscillation. exemple 455 Maximum deflection in an oscillation or wave.

Question 203-40 : The definition of frequency modulation is ?

The information is carried by a modification of the frequency of the carrier.

.frequency modulation the information that is impressed onto the carrier wave by altering the frequency of the carrier.. 2560 exemple 459 The information is carried by a modification of the frequency of the carrier.


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