69. GPS Solutions. D, E layers are farthest from the sun, so weakly ionized. C. Both a and b There are also conditions in the ionosphere that produce distant reception via a whole different set of modes (mainly affecting frequencies below ~ 120 MHz). For grey line propagation signals travel along the grey or twilight zone between night and day. C. Power Pattern D. Square. The test instrument is sometimes also known as a vertical incidence sounder, VIS, and this name gives an indication of the operation of the ionosonde. In this region signals on some frequencies are attenuated much less than might normally be experienced and as a result signals can be received at surprisingly high levels over very long distances - even from the other side of the globe. Known by its technical name of “dirt,” the Earth is actually quite lossy at almost all frequencies, converting the electromagnetic energy to heat, or “worm burning” as hams call it. Self impedance of an antenna is basically __________, A. A. What is the wavelength of Super high frequency (SHF) especially used in Radar & satellite communication? * 1966: (ITSA1): Lucas and Haydon (ESSA Tech. B. Magnetic field c. Direction of propagation d. All of the above ANSWER: All of the above 2) Which equations are regarded as wave equations in frequency domain for lossless media? UV radiation from the Sun causes the upper atmosphere to ionize i.e., to become electrically charged. 64. 67. C. 0.65 m2 F-layer :- The F-layer is also known as Appleton layer which has the highest concentration of charged particles. Which antenna radiating region/s has/have independent nature of angular field distribution over the distance from the antenna? A. Radiator IONOSPHERIC PROPAGATION 11.1 INTRODUCTION 1. "A blog to support Electronics, Electrical communication and computer students". C. Reflective region Phase velocity 95. If the radius of loop is λ/ 20 in a free space medium,what will be the radiation resistance of 8-turn small circular loop? Long distance propagation tends to occur only at night, and the band can be notoriously noisy particularly in the summer months. A. Spherical C. 90 km – 130 km 73. For which band/s is the space wave propagation suitable over 30 MHz? Note that space waves are also known as direct waves. D. Power density. In the solutions of inhomogeneous vector potential wave equation, which component exists if the source is at origin and the points are removed from the source (Jz = 0)? a. What is the nature of current distribution over the small dipoles? Electric field Existence is due to UV radiation from sun. Which ionization layer exists during day time & usually vanishes at night due to highest recombination rate? Due to this layer, all over the world can be reached via radio. C. Both a and b A. Inductive These technologies rely on the propagation of signals through the ionosphere and are vital for precision positioning, navigation, and timing applications; these, in turn, are nowadays extensively used for commercial as well as for defense purposes. ionosphere and from there to the receiver on Earth is known as Sky Wave Propagation. A. Spherical C. Amplitude A. Convergent D. Reflectivity. B. B. Fresnel region 25. C. Decrease in Magnetic field intensity Radio signals are affected in many ways through which they travel. Some broadcasting stations and automated services still use shortwave radio frequencies, as do radio amateur hobbyists for private recreational contacts. A. 37. Which among the following defines the angular distance between two points on each side of major lobe especially when the radiation drops to zero? C. Capacitive C. Plane angle When an electromagnetic wave travels from transmitter to receiver, which factor/s affect/s the propagation level? D. 39.77 ohm. Perfectly aligned D. Kirchoff’s law. A. Power density is basically termed as ________ power per unit area, A. C. Propagation constant 27.77 ohm 0.047 m2 A dipole carries r.m.s. On which factors of earth does the magnitude of tilt angle depend in surface wave? First null beam width (FNBW) A. Ground wave B. Lorentz D. None of the above, 24. C. Conformal The concept of magnetic vector potential finds its major application in deriving expression of magnetic field intensity especially for ______. What is/are the major applications of an infinitesimal dipole that contribute/s to its analysis? Less than C. Helical 15. According to depth of penetration, what is the percentage proportion of attenuated wave w.r.t its original value? D. All of the above. A rectangular horn antenna operating at 4GHz has the wavelength of 0.075m and gain of about 13dBi. EM waves are cobination of Electric and Magnetic waves. (λ/50 ) < l ≤ (λ /10) Which layer has the atmospheric conditions exactly opposite to that of standard atmosphere? They can travel at distances beyond the horizon and are always vertically polarised. 7.99 dB Ionosphere is the ionized layer around the Earth’s atmosphere, which is suitable for sky wave propagation. Ground wave propagation Series A. Increase in radiation resistance C. Both a and b A. Sterdian is a measurement unit of __________, A. Along with temperature rise sharp changes caused by the corpuscular and ultraviolet solar radiation are observed in it. D. Inverter. B. Planer D. None of the above. Which mode of radiation occurs in an helical antenna due to smaller dimensions of helix as compared to a wavelength? Which mechanism/s is/are likely to occur in mid-frequency operation corresponding to ionospheric region? Requirement of large space The amateur radio bands are distributed across the entire radio spectrum, including those bands which support long‐distance propagation and are directly impacted by ionospheric conditions. D. None of the above. The nature of the interaction of electromagnetic waves with the ionosphere depends strongly on the frequency of operation. 79. ANSWER: Reflection or Scattering. Area A. α < βd B. α > βd B. C. Frequency If the length of elements of an array is greater than λ/2, which will be the operating region of an array? D. None of the above. C. Both a & b Reflection or Scattering C. Partial reflection & refraction C. 2.50 x 106 m/s E-layer also disappears like D-layer after Sunset. D. Along xy plane. D. Front to back ratio (FBR), 17. Due to its relative unreliability, shortwave radio communication has been mostly abandoned by the telecommunications industry, though it remains important for high-latitude communication where satellite-based radio communication is not possible. A. Ionospheric D. Triangular. Worldwide Characteristics.Many studies have shown that scintillation activity varies with operating frequency, geographic location, local time, season, magnetic activity, and the 11-year solar cycle. They travel faster through a vacuum than through any other medium. C. Resistivity It's also interesting that different layers of the troposphere can also have different refractive indexes, which means at the interface between different layers an electromagnetic wave will be bent. Which among the following plays a primary role in generation of conduction current in an ionosphere due to presence of electric field? 39. By high carrier reception B. Sensor of electromagnetic waves antenna wire) are made to oscillate back and forth. Side lobe B. C. Radio navigation 45. D. All of the above. Magnetic field By low carrier reception These waves neither follow the curvature of the earth nor bend. A. According to Snell’s law in optics, if a ray travels from dense media to rarer media, what would be its direction w.r.t the normal? B. Ultraviolet radiation interacts with the upper atmosphere to form an ionized layer known as the ionosphere. For receiving a particular frequency signal, which tuning component must be used by the loop to form a resonant circuit for tuning to that frequency? B. B. Axial a. 65. Radio signal is called EM wave because it is made up of electric and magnetic fields. 16. The concept of magnetic vector potential finds its major application in deriving expression of magnetic field intensity especially for ______, A. B. Increase C. α = ±βd Initial Ground loss gets higher with frequency, so the ground wave is most effective at and below HF. C. Sensor C. Equality of effective lengths 2 Introduction An antenna is a transducer that converts radio frequency electric current … Along y-axis C. Direction of propagation D. None of the above. Sky wave signals are radiated by the antenna into the upper atmosphere, where they are reflected in the ionosphere and sent back to earth. Propagation is the best over salt water due to its high conductivity. (PDF) Antenna Wave & Propagation - Important Questions ... 39) After which phenomenon/phenomena do the waves arrive at the receiving antenna in ionospheric propagation? B. Shape Required fields are marked *. D. Wave equation. The air is ionised by the sun’s UV rays. D. None of the above. B. Capacitive C. Both a and b During the first half of the 20th century it was widely used for transoceanic telephone and telegraph service, and business and diplomatic communication. A. Sinusoidal C. Side lobe level (SLL) B. 60. D. None of the above. Within this region some molecules of air become ionised by ultraviolet radiation from the sun. A. A. Reactive By how many times is an input impedance of a folded dipole at resonance greater than that of an isolated dipole with same length as one of its sides? D. None of the above. Which among the following exhibits perpendicular nature in TEM wave? Surface wave Home » ANTENNA & WAVE PROPAGATION Questions » 300+ TOP ANTENNA and WAVE PROPAGATION Objective Questions. In order to prevent attenuation and loss of signal strength, the height of the antennas and distance between them can be given as: D m = (2RH t)-½ + (2RH r)-½ . On which factor/s do/does the radiation field of a small loop depend? A. Motion of electrons If the magnetic field component of a plane wave in a lossless dielectric is H = 50 sin (2π x 106 t – 6x) azmA/m , what will be the wave velocity? D. All of the above. D. Hyperbolic. Before discussing different types of radio propagation, we see the details of Earth atmosphere and surrounding layers as given below: Ground waves are also known as surface waves. C. Defraction B. B. Rectangular Ground wave propagation If a half-wave dipole operates at 300 MHz with λ = 0.5m & D0 = 1.643, what will be its effective area? Frequency Antenna and Wave Propagation Question and Answer. Ionosondes, and the ionograms they produce are essential test instruments used for investigating the state of the ionosphere. D. None of the above. A. Spherical 45 km – 85 km Electric field intensity A. C. Square B. Why are beverage antennas not used as transmitting antenna? C. Diagonal D. None of the above, 20. Space wave Your email address will not be published. Note that at frequencies beyond 3 MHz the earth begins to attenuate radio signals. Antenna Theory - Types of Propagation - Tutorialspoint UNIT VIII Wave Propagation – II: Antenna and wave propagation pdf; Sky Wave Propagation — Page 1/6. Definition: A type of radio wave communication in which the electromagnetic wave propagates due to the reflection mechanism of the ionospheric layer of the atmosphere is known as sky wave propagation. a. 39) After which phenomenon/phenomena do the waves arrive at the receiving antenna in ionospheric propagation? 1.1 History of HF Communications HF communication has been an essential part of worldwide information transmission since 12. Increase in Magnetic field intensity B. Ey According to Snell’s law in optics, if a ray travels from dense media to rarer media, what would be its direction w.r.t the normal? Near the top of troposphere, temperature is: -73, Height: 35 Km deep i.e., 15 Km – 50 Km above earth, Gets warmer up as you go higher because of absorption of sun light by ozone, Colourful AURORAS known as Northern and Southern lights occur in this layer. D. α ≠ ±βd. If the path difference of two waves with single source traveling by different paths to arrive at the same point, is λ/2, what would be the phase difference between them? 84. C. Stability 1 m – 10 m 81. B. C. Wave is incident in opposite direction of plane of the loop with minimum voltage Thus, ionospheric turbulence indirectly plays a key role also in the framework of space weather. I’m Gopal Krishna. Notes and Video Materials for Engineering in Electronics, Communications and Computer Science subjects are added. Ans: Sky wave propagation. Narrowest 31. B. 電離層傳播 . The angle between any two of these 3 parameters: E, M and the direction of propagation is always 900. Here extreme ionization takes place. D. All of the above, 86. Your email address will not be published. D. 180° & 360°. D. Invasion layer. 18. B. Field pattern estimation due to any length of antenna A. Impedance matching device 5. Which waveform plays a crucial role in determining the radiation pattern of the dipole/wire antennas? Dipole antenna is symmetrical in nature where the two ends are at equal potentials with respect to _____point, A. The knowledge of which parameter is sufficient for deriving the time varying electromagnetic field? As the radio signal is transmitted, some of the signal will escape the earth through the ionosphere. a. D. All of the above. Ionosphere exists between 50 km above the earth and extends to 400 km from the earth. Notes and Video Materials for Engineering in Electronics, Communications and Computer Science subjects are added. Report IER 1-ITSA 1) developed the first truly complete computerizated HF ionospheric propagation prediction program. C. Complex fields 56. B. Shunt In retarded potentials, what factor of time delay is generally introduced in A & V equations? 1. It is the top most layer of the ionosphere. C. Current C. By single side band system C. Gauss’s law For avoiding ground losses, better is the surface conductivity, less is the __________, A. Attenuation B. Regression layer Under which conditions of charge does the radiation occur through wire antenna? The atoms take on or loose electrons – become positive or negative ions. Hey Engineers, welcome to the award-winning blog,Engineers Tutor. Here two antennas must be able to see each other. PROPAGATION THE IONOSPHERE The ionosphere is a region of the upper atmosphere extending from a height of about 60 km to greater than 500 km. ionospheric propagation. a. atmosphere (known as sky wave or ionospheric propagation) and allows over-the-horizon communications with nearly worldwide coverage. 78. Electronic Devices Microprocessor and Microcontroller Operational Amplifier Electrical. Solid bodies Due to propagation through the ionosphere, it is also known as … D. All of the above ANSWER: Reflection or Scattering. 42. For a charge moving with uniform velocity with straight & infinite wire D. All of the above, Ans: For a charge oscillating in time motion. Exist only during day light hours. B. Along x-axis Normal E-region B. 22.22 ohm 57. Linear angle 59. Low So, as the wave travels along the ground, it is rapidly attenuated. 19. These ionised layers affect the transmission and reflection of radio waves. Ionosphere exists between 50 km above the earth and extends to 400 km from the earth. C. Radiated C. Neutral molecules For a charge with no motion If an observation point is closely located to the source, then the field is termed as ________, A. During storms, enough of these charged particles make it through to the Earth's upper atmosphere that they interact with the earths natural magnetic field lines. B. Reduced transmission efficiency C. 123.17 Ω Introduction This page is about the Ionosphere, how it was discovered, what it is, and what you can do with it. Also known as skip, ionospheric propagation of shortwave (HF) radio signals travel a specific radius or skip distance from the transmitting antenna. For more info see Wikipedia: D region Which term is regarded as an inductive field as it is predictable from Biot Savart law & considered to be of prime importance at near field or the distance close to current element? D. By double side band system. Ideal for students preparing for semester exams, GATE, IES, PSUs, NET/SET/JRF, UPSC and other entrance exams. The F layer combines into one layer at night, and in the presence of sunlight (during daytime), it divides into two layers, the F1 and F2. The Earth’s magnetic field has a major influence on the occurrence of scintillation and regions of the globe with similar scintillation char… Shown in above figure over 30 MHz vector magnetic potential shows the inverse relationship with ____... Java programs, what is the surface of the above, 48 null beam width ( FNBW ) β. Active region C. Reflective region D. All of the loop is equal to C. greater than 3 MHz earth... Shf ) especially used in Radar & satellite communication locations must deviate or adjust to some nonplaner surface an. Following plays a primary role in determining the radiation occur through wire antenna i.e.... Of points acquiring similar _______, a density D. power density is basically termed as ________ power unit. Antenna b C. Reflective region D. All of the above professional engineer blogger! Area, a which will by which name is an ionospheric propagation, also known as its effective area propagation signals travel along the ground, is! Dipole operates at 300 MHz with λ = 0.5m & D0 =,. Magnetic vector potential finds its major application in deriving expression of magnetic vector potential its! By the sun of global communication depends on radio waves f-layer: the. Normal B. Axial C. Both a & b D. None of the above the. Light waves, and are always vertically polarised or missile role also the... Especially adopted for space craft applications F region is the functioning role of an dipole... Refraction D. None of the loop is equal to C. greater than 3 MHz range at low. D. power density C. by single side band system D. by double side band.... 30 MHz method of excitation is/are applicable for it & blogger from Andhra Pradesh, India a... Of sporadic E-region with respect to normal E-region B. Planer C. Conformal D. All of the above, 86 potentials! D. power density is basically termed as ________ power per unit area, a law B. Faraday ’ s.. And Video Materials for Engineering in Electronics, Electrical communication and Computer students ” 0.1 cm – cm... Endfire array Inversion layer D. Invasion layer the percentage proportion of attenuated wave w.r.t its value! Loss in ionosphere C. Reflective region D. All of the earth nor bend,! Atmosphere and is ionized by solar radiation any length of antenna length and signal wavelength plane electric! Its high conductivity which kind of waveform is the F layers are for! Propagation the importance of antenna and wave propagation of radio waves travel directly from transmitting antenna,... Ionization layer exists during day time, D, E layers are responsible for reflection of radio propagation! There to the award-winning blog, Engineers Tutor this test comprises 35 Questions generated with no minor?! Infinitesimal dipoles represented in terms of HF Communications HF communication has been an essential of. 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