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Multiple > protocol : A loop antenna is a commonly used for ?

Question 175-1 : Adf receivers airborne weather radars gps transmitters satellite transmitters

.the aircraft equipment consists of two antennas the adf receiver and the adf instrument .two antennas are used the loop antenna and the sense antenna .the loop antenna can sense the direction of the signal from the station but cannot discriminate whether the station is in front or behind the aircraft the sense antenna can discriminate direction and solves the ambiguity of the loop antenna exemple 275 adf receivers.adf receivers.

Vlf very low frequency waves appear in the frequency spectrum ?

Question 175-2 : 3 khz 30 khz 30 mhz 300 mhz 300 mhz 3000 mhz 3 ghz 30 ghz

. 1682 exemple 279 3 khz - 30 khz3 khz - 30 khz

Lf low frequency waves appear in the frequency spectrum ?

Question 175-3 : 30 khz 300 khz 30 hz 300 hz 300 mhz 3000 mhz 3 mhz 30 mhz

. 1682 exemple 283 30 khz - 300 khz30 khz - 300 khz

Mf medium frequency waves appear in the frequency spectrum ?

Question 175-4 : 300 khz 3000 khz 30 mhz 300 mhz 3 mhz 30 mhz 30 ghz 300 ghz

. 1682 exemple 287 300 khz - 3000 khz300 khz - 3000 khz

Hf high frequency waves appear in the frequency spectrum ?

Question 175-5 : 3 mhz 30 mhz 30 mhz 300 mhz 300 mhz 3000 mhz 3 khz 30 khz

. 1682 exemple 291 3 mhz - 30 mhz3 mhz - 30 mhz

Uhf ultra high frequency waves appear in the frequency spectrum ?

Question 175-6 : 300 mhz 3000 mhz 30 mhz 300 mhz 3 mhz 30 mhz 3 ghz 30 ghz

. 1682 exemple 295 300 mhz - 3000 mhz300 mhz - 3000 mhz

Shf super high frequency waves appear in the frequency spectrum ?

Question 175-7 : 3 ghz 30 ghz 30 mhz 300 mhz 3 mhz 30 mhz 300 mhz 3000 mhz

. 1682 exemple 299 3 ghz - 30 ghz3 ghz - 30 ghz

Ehf extremely high frequency waves appear in the frequency spectrum ?

Question 175-8 : 30 ghz 300 ghz 30 mhz 300 mhz 3 mhz 30 mhz 3 ghz 30 ghz

. 1682 exemple 303 30 ghz - 300 ghz30 ghz - 300 ghz

Which of the following term describes the maximum deflection in an oscillation ?

Question 175-9 : Amplitude phase period frequency

. /com en/com062 587 jpg.amplitude maximum deflection in an oscilliation exemple 307 amplitude.amplitude.

Frequency is defined as the ?

Question 175-10 : Number of cycles occurring in one second in a radio wave expressed in hertz hz maximum deflection in a radio wave expressed in hertz hz minimum number of cycles occurring in one minute in a radio wave expressed in hertz hz length of a radio wave expressed as an angle

.a cycle is any complete round or series of occurrences that repeats or is repeated . 2549.the frequency is the number of cycles occurring in one second in a radio wave expressed in hertz hz exemple 311 number of cycles occurring in one second in a radio wave expressed in hertz (hz).number of cycles occurring in one second in a radio wave expressed in hertz (hz).

Single sideband modulation sbb is a modulation technique where only one ?

Question 175-11 : Hf volmet and hf two way communication hf one way communication vhf communication and hf volmet vhf vor and gnss

.there is redundancy in double sideband transmissions in that the information is contained in both the upper and lower sidebands additionally the original rf carrier wave having served its purpose to get the audio information into radio frequencies is now redundant so it is possible to remove one of the sidebands and the carrier wave because the remaining sideband contains all the information this is known as single sideband ssb operation .when using sky wave propagation for communication the differing refraction occurring at different frequencies leads to an increase in distortion if the bandwidth is too large the ionosphere comprises electrically charged particles which cause high levels of static interference on radio waves the use of ssb significantly reduces the effect of this interference the mf and hf frequencies used for long range communication are in great demand hence the use of ssb transmissions increases the number of channels available the use of ssb also reduces theamount of power required exemple 315 hf volmet and hf two-way communication.hf volmet and hf two-way communication.

Which statement about vhf/uhf frequencies is correct ?

Question 175-12 : For both vhf/uhf propagation the space wave is the only propagation path of practical use there is no sky wave under normal conditions vhf has under normal conditions a sky wave wherease uhf has not for both vhf/uhf propagation the space wave is the main propagation path vhf frequencies below 120 mhz may be subjected to sporadic e reflection and then have a sky wave for both vhf/uhf the surface wave is the main propagation path of practical use neither vhf/uhf has a sky wave under any conditions for vhf the surface wave is the main propagation path and for the uhf the space wave

.radio waves in vhf uhf shf and ehf propagate as space waves .radio waves in vlf lf mf and hf propagate as surface/ground waves and sky waves exemple 319 for both vhf/uhf propagation, the space wave is the only propagation path of practical use. there is no sky wave under normal conditions.for both vhf/uhf propagation, the space wave is the only propagation path of practical use. there is no sky wave under normal conditions.

Diffraction is the process by which ?

Question 175-13 : Radio wave travel over and around obstacles a space wave penetrates the ionosphere a ground wave is attenuated over rough ground a direct wave is bent around the form of the earth

.diffraction is the phenomenon by which wave energy bends around an object exemple 323 radio wave travel over and around obstacles.radio wave travel over and around obstacles.

Antennas.an ac will be induced ?

Question 175-14 : In a wire parallel to a wire fed with an ac but remote from it in a wire perpendicular to the wire fed with an ac but remote from it in a wire parallel to the wire fed with a dc but remote from it in a wire connected in series to a wire fed with a dc

.inductive coupling refers to the phenomenon that exists when a magnetic field created by an electrical current induces an effect on something else when this happens the two then become mutually reactive or coupled by the inductive effects of the magnetic field for example when an electrical current passes through a wire the electromagnetic field created can induce an electrical current in another wire causing the two to be inductively coupled the principles and effects of inductive coupling find use in devices such as transformers and electric motors.the effects of inductive coupling can be used in one of three primary ways first the inducing field can create a specifically desired electrical current such as in transformers second the inducing field can create a specifically desired mechanical effect such as in electric motors finally the inducing field can create a resonance which itself can create specifically desired electrical currents such as in radio transmission and reception and non contact charging devices.in transformers an electrical current conducts through a wire wound around a core of some type called the primary winding this wire is intentionally placed near another wire wound around the same core called the secondary winding .the electromagnetic field created by passing current through the primary winding then induces an electrical current in the secondary winding.resonant devices work in a way similar to transformers though without the paired windings in these devices a standing electromagnetic field is created when this field encounters an antenna the effect of inductive coupling causes the antenna to resonate which in turn induces an electrical current at its feed point in the case of a radio the induced current is amplified and heard over the radio in a charging device the induced current is directly applied to a battery's terminals to recharge it exemple 327 in a wire, parallel to a wire fed with an ac, but remote from it.in a wire, parallel to a wire fed with an ac, but remote from it.

In aviation the reflection on ionosphere layers phenomenon is used in the ?

Question 175-15 : Hf uhf vlf vhf

.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 331 hf.hf.

The wavelength of a radio signal transmitted at the frequency 118 7 mhz is ?

Question 175-16 : 2 53 m 25 3 m 2 53 cm 25 3 cm

.wavelength meters = speed of light / frequency..wavelength = 300 000 000 / 118 700 000 = 2 53 m exemple 335 2.53 m.2.53 m.

In the propagation of mf waves the phenomenon of fading is particularly found ?

Question 175-17 : At night due to the combination of the sky and ground waves by day due to the combination of sky and ground waves at night and when raining by day and when raining

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

A radio signal looses strength as range from the transmitter increases this is ?

Question 175-18 : Attenuation refraction propagation ducting

.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 343 attenuation.attenuation.

Skip distance is the ?

Question 175-19 : Range from the transmitter to the first sky wave highest critical frequency distance wavelength distance of a certain frequency thickness of the ionosphere

.skip distance is the distance between the transmitter and the point on the surface of the earth where the first sky return arrives exemple 347 range from the transmitter to the first sky wave.range from the transmitter to the first sky wave.

The wavelength of a radio transmitted on frequency 121 95 mhz is ?

Question 175-20 : 2 46 m 24 60 cm 2 46 cm 24 60 m

.wavelength meters = speed of light / frequency..wavelength = 300 000 000 / 121 950 000 = 2 46 m exemple 351 2.46 m.2.46 m.

What describes polarization ?

Question 175-21 : Orientation of the plane of oscillation of the electrical component of the electromagnetic wave orientation of the antenna to the north pole orientation of the plane of oscillation of the magnetic component of the electromagnetic wave rotation of the antenna around a fixed axis

. 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 355 orientation of the plane of oscillation of the electrical component of the electromagnetic wave.orientation of the plane of oscillation of the electrical component of the electromagnetic wave.

Modulation is ?

Question 175-22 : Addition of a low frequency signal tone voice onto high frequency carrier wave elimination of disturbances for improving reception tuning receiver into the frequency of the transmitter addition of a high frequency signal tone voice onto low frequency carrier wave

.modulation is addition of information onto a radio wave during transmission .the goal is to modify the radio frequency signal in order to superimpose audio and/or data signal a low frequency signal will be modulated by changing one ore more of its parameters amplitude frequency phase and then added onto a carrier wave which consists of a high frequency this process is known as 'modulation' and is necessary for transporting information via cable or through the air exemple 359 addition of a low frequency signal (tone, voice) onto high frequency carrier wave.addition of a low frequency signal (tone, voice) onto high frequency carrier wave.

On which bearings errors caused by the shoreline/coastal effect reach their ?

Question 175-23 : Bearings 000° 030° degrees to the coastline bearings 030° 060° degrees to the coastline bearings perpendicular to the coastline any bearings in hf band

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 363 bearings 000°-030° degrees to the coastline.bearings 000°-030° degrees to the coastline.

The doppler effect onto the radio signals is ?

Question 175-24 : The shift of frequency of the wave due to the relative movement between the transmitter and the receiver increasing or decreasing of the emitting aircraft ground speed the interference between the direct wave and that reflected by the ground the fluctuation of their propagation velocity

exemple 367 the shift of frequency of the wave due to the relative movement between the transmitter and the receiver.the shift of frequency of the wave due to the relative movement between the transmitter and the receiver.

The d layer and e layer of the atmosphere are part of the ?

Question 175-25 : Ionosphere troposphere tropopause stratosphere

. 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 371 ionosphere.ionosphere.

When raising the frequency of an electromagnetic wave the ?

Question 175-26 : Wavelength decreases wavelength and amplitude increases wavelength remains the same wavelength increases

.the relationship between wavelength and frequency is .wavelength = speed of light / frequency..if frequency increases wavelength decreases exemple 375 wavelength decreases.wavelength decreases.

The phenomenon when a wave bends when it passes around an impenetrable obstacle ?

Question 175-27 : Diffraction attenuation refraction propagation

.diffraction is the phenomenon by which wave energy bends around an object exemple 379 diffraction.diffraction.

The phenomenon of a change in direction of an radio wave em wave occurring due ?

Question 175-28 : Refraction absorption diffraction attenuation

.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 383 refraction.refraction.

A reason that gps satellites use helical antennae is ?

Question 175-29 : That the signal has a circular polarization that the signal has a linear polarization the reduced size of the antennae the reduced weight of the antennae

.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 387 that the signal has a circular polarization.that the signal has a circular polarization.

The mix of an electromagnetic wave with another is called ?

Question 175-30 : Interference reflection diffraction refraction

.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 391 interference.interference.

Speed of a radio wave ?

Question 175-31 : 300 000 km/s 300 000 m/s 300 000 km/h 300 000 m/h

exemple 395 300 000 km/s.300 000 km/s.

For long range ndb's the most common type is ?

Question 175-32 : Lf non a1a mf non a1a mf non a2a lf non a2a

.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 399 lf, non a1a.lf, non a1a.

Mountain effect occurring for instance with ndbs is caused by what physical ?

Question 175-33 : Reflection diffraction absorption refraction

.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 403 reflection.reflection.

Which physical effects affecting wave propagation as shown in the figure . 2556 ?

Question 175-34 : A = refraction b = absorption c = reflection a = diffraction b = reflection c = reflection a = absorption b = absorption c = diffraction a = refraction b = attenuation c = interference

exemple 407 a = refraction b = absorption c = reflectiona = refraction b = absorption c = reflection

Which letter in the figure below indicates the 'skip zone' . 2557 ?

Question 175-35 : C d a b

.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 411 c.c.

Which letter in the figure below indicates the 'skip distance' . 2557 ?

Question 175-36 : D c a b

.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 415 d.d.

You are flying over sea parallel to the coastline an ndb is situated 10 nm ?

Question 175-37 : Sectors a + b sectors a + d sectors c + d sectors b + d

.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 419 sectors a + bsectors a + b

You are flying parallel to the coastline an ndb is positioned about 10 nm ?

Question 175-38 : Area c + d deflection to the coastline area a + b deflection to the coastline area a + d deflection to the coastline area b + 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 423 area c + d, deflection to the coastline.area c + d, deflection to the coastline.

The phenomenon of a change in direction of an em wave occurring at an interface ?

Question 175-39 : Reflection diffraction absorption refraction

Ecqb03 august 2016 exemple 427 reflection.reflection.

What is required to enable an antenna to transmit an electromagnetic wave ?

Question 175-40 : The antenna has to be fed with an alternating current of high frequency the antenna mast must be normal to the ground the antenna has to be fed with a direct current of high frequency the antenna has to be fed with a direct current of low frequency

Ecqb03 august 2016 exemple 431 the antenna has to be fed with an alternating current of high frequency.the antenna has to be fed with an alternating current of high frequency.

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