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Electric field b. The most glaring example of absorption that normally plays a spoil-sport in HF propagation is the well known ionospheric D-layer absorption of radio waves. B. Outward B. Vertical D. Decrease in radiation resistance 39) After which phenomenon/phenomena do the waves arrive at the receiving antenna in ionospheric propagation? ANSWER: Reflection or Scattering. Ans: Both A and B B. Conductivity Ans: Reflection or Scattering Sea wave propagation B. B. Equal to (λ/50 ) < l ≤ (λ /10) What is/are the major applications of an infinitesimal dipole that contribute/s to its analysis? C & D 4 In the Northern and Southern pole regions of the Earth, passive observations of optical and radio emissions generated in the ionosphere, bouncing radio waves of different frequencies from it. 42. Hence, the electromagnetic "ray" is bent away from the normal rather than toward the normal as would be indicated when the refractive index is greater than unity. D. Square B. Axial In the early 1930s, test transmissions of Radio Luxembourg inadvertently provided evidence of the first radio modification of the ionosphere; HAARP ran a series of experiments in 2017 using the eponymous Luxembourg Effect.[7]. Ans: λ C. Both a and b A. Source What would be the power radiated by an antenna? A. Ans: All of the above The oscillating electrons will then either be lost to recombination or will re-radiate the original wave energy. Ans: Divergent Solar heating and tidal oscillations in the lower ionosphere move plasma up and across the magnetic field lines. Incoherent scatter radars operate above the critical frequencies. 90° & 180° C. 2.50 x 106 m/s They include: A variety of experiments, such as HAARP (High Frequency Active Auroral Research Program), involve high power radio transmitters to modify the properties of the ionosphere. D. None of the above F-layer :- The F-layer is also known as Appleton layer which has the highest concentration of charged particles. A. Above that is the stratosphere, followed by the mesosphere. B. Sensor of electromagnetic waves 11. A. Reactive near-field region Plane to spherical wave a. C. 18 MHz 40) By which name/s is an ionospheric propagation, also known as? Heaviside's proposal, coupled with Planck's law of black-body radiation, may have hampered the growth of radio astronomy for the detection of electromagnetic waves from celestial bodies until 1932 (and the development of high-frequency radio transceivers)[citation needed]. B. F2 layer of appleton region acts as a significant reflecting medium for _____ frequency radio waves current of about 300A across the radiation resistance 2 Ω. Test Set - 2 - Antenna & Wave Propagation - This test comprises 35 questions. During the daylight hours in the midlatitudes, the ionospheric delay may grow to be as much as five times greater than it was at night, but the rate of that growth is seldom more than 8 cm per minute. It is calculated as shown below: where N = electron density per m3 and fcritical is in Hz. A. C. Wave is incident in opposite direction of plane of the loop with minimum voltage The anomaly is always present in the northern hemisphere, but is usually absent in the southern hemisphere during periods of low solar activity. C. Resistivity Ionospheric databases have hith-erto concentrated on scaled parameters, but to advance our understanding of ionospheric propagation ef-fects more detail is needed. At the magnetic dip equator, where the geomagnetic field is horizontal, this electric field results in an enhanced eastward current flow within ± 3 degrees of the magnetic equator, known as the equatorial electrojet. A. B. Elliptical Along x-axis 61. The critical frequency is the limiting frequency at or below which a radio wave is reflected by an ionospheric layer at vertical incidence. For avoiding ground losses, better is the surface conductivity, less is the __________ A. In radio communication link, what is the shape/nature of waves generated by transmitting antenna? A. Spherical B. A. Ratcliffe researched the topic of radio propagation of very long radio waves in the ionosphere. 1) Which among the following exhibits perpendicular nature in TEM wave? At the center of the HAARP research facility is a high power, High-Frequency (HF) phased array radio transmitter, known as the Ionosphere Research Instrument (IRI). A. Impedance matching device The permissible frequency range in the case of sky wave propagation lies between 3 … C. Both a and b In 1962, the Canadian satellite Alouette 1 was launched to study the ionosphere. A. The F layer consists of one layer (F2) at night, but during the day, a secondary peak (labelled F1) often forms in the electron density profile. If an observation point is closely located to the source, then the field is termed as ________ B. Ey Ans: A & B D. 57% This enables the construction of bottom-side ionospheric profiles, and also provides a large of body of data ca- Why are beverage antennas not used as transmitting antenna? ionospheric error, conducted via the utilzation of GPS measurements collected by continuous-ly operating stations in Campania. For which band/s is the space wave propagation suitable over 30 MHz? D. Gyrator B. [21] Ionospheres have also been observed at Io, Europa, Ganymede, and Triton. 72. 0° & 180° In … C. Elliptical Ground wave propagation C. Sky wave propagation D. All of the above Ans: Sky wave propagation 41. A. At night the E layer weakens because the primary source of ionization is no longer present. * 1950: Laitinen and Haydon (Tech. A & C Induced By low carrier reception B. Capacitive B. Ground wave propagation What is the nature of radiation pattern of an isotropic antenna? Discovery. Ans: 180 kW, Your email address will not be published. Associated with solar flares is a release of high-energy protons. E-layer also disappears like D-layer after Sunset. A. A. C. Array very modest equipment and antennas—a fact well known to radio amateurs. A. B. Microstrip When a radio wave reaches the ionosphere, the electric field in the wave forces the electrons in the ionosphere into oscillation at the same frequency as the radio wave. C. Mid A. In which kind of waveform is the phase velocity defined? C. Plane angle B. Equality of impedances Ans: All of the above In this process the light electron obtains a high velocity so that the temperature of the created electronic gas is much higher (of the order of thousand K) than the one of ions and neutrals. C. Defraction D. Congruent 27% Increase in radiation resistance Ans: Resistive D. All of the above C. Interference of normal radiation & radio wave propagation A & B A. 46. ionosphere (īŏn`əsfēr), series of concentric ionized layers forming part of the upper atmosphere atmosphere [Gr.,=sphere of air], the mixture of gases surrounding a celestial C. Both a & b A geomagnetic storm is a temporary intense disturbance of the Earth's magnetosphere. A. Permittivity B. 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? Electric field intensity Ans: Perfectly aligned Maurice V. Wilkes and J. The concept of magnetic vector potential finds its major application in deriving expression of magnetic field intensity especially for ______ Introduction. B. Low 10. Ans: Sinusoidal In an electrically small loops, the overall length of the loop is ______ one-tenth of a wavelength. B. C. Current D. Reflectivity D. α ≠ ±βd What is the functioning role of an antenna in receiving mode? A. Ionospheric propagation can also be classified by character. Tilt angle B. 60. The F2 layer persists by day and night and is the main region responsible for the refraction and reflection of radio waves. Persistent anomalies to the idealized model, X-rays: sudden ionospheric disturbances (SID), Ionospheres of other planets and natural satellites, Heaviside's proposal, coupled with Planck's law of black-body radiation, may have hampered the growth of radio astronomy for the detection of electromagnetic waves from celestial bodies until 1932 (and the development of high-frequency radio transceivers), The government thought those frequencies were useless, Super Dual Auroral Radar Network (SuperDARN), High Frequency Active Auroral Research Program, TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics), Fessenden and Marconi: Their Differing Technologies and Transatlantic Experiments During the First Decade of this Century, "Firsts in the Space Race. Normal E-region Ans: Narrowest During the first half of the 20th century it was widely used for transoceanic telephone and telegraph service, and business and diplomatic communication. C. Side lobe level (SLL) 50.45 Ω C. Circular Ans: Less than A. λ/2 Ionospheric-Propagation Predictions April 1969 Electronics World: April 1969 ... although not to as great an extent. A. This region above the F layer peak and below the plasmasphere is called the topside ionosphere. [5] However, Marconi did achieve transatlantic wireless communications in Glace Bay, Nova Scotia, one year later.[6]. D. 1/ r4 SKY WAVE (or IONOSPHERE) Propagation. Wavefront is basically a locus of points acquiring similar _______ Nonhomogeneous structure of the electron/ion-plasma produces rough echo traces, seen predominantly at night and at higher latitudes, and during disturbed conditions. B. After sunset an increase in the height of the E layer maximum increases the range to which radio waves can travel by reflection from the layer. This effect is known as the winter anomaly. There are, however, several drawbacks to this solution. The effect was discovered by John Howard Dellinger around 1935 and also described by the German physicist Hans Mögel (1900-1944) in 1930. Reflection or Scattering b. Refraction c. Defraction d. All of the above. Ans: Resistive 2 88. Which among the following plays a primary role in generation of conduction current in an ionosphere due to presence of electric field? As soon as the X-rays end, the sudden ionospheric disturbance (SID) or radio black-out ends as the electrons in the D-region recombine rapidly and signal strengths return to normal. Shape A & B It is the layer with the highest electron density, which implies signals penetrating this layer will escape into space. So, frequencies greater than 3 MHz range, ground wave propagation is not significant or used. A. Attenuation The frequency of the radio wave determines many of the characteristics of the transmission. Surface wave D. Power density Ans: High B. 98. Ans: Normal C. Resistive Ans: 123.17 Ω This change in the electron profile of ionosphere is known as Sudden Ionospheric Disturbances (SID) [12]. Ionospheric propagation occurs when the upper layers of the Earth's atmosphere is excited by solar activity, creating a mirror effect reflecting radio signals back to earth many miles further than would be possible by line of site. Ans: Triangular A. B. The best known long-term performance prediction methods involve the used of large-scale computer programs. B. Ans: All of the above In solution evaluation process of inhomogeneous vector potential wave equation, if points are completely removed from the source, then by which factor does the time varying field & static solution differ? In empirical models of the ionosphere such as Nequick, the following indices are used as indirect indicators of the state of the ionosphere. D. 9.02 dB Which among the following is regarded as a condition of an ordinary endfire array? B. B. Ans: Metallic device for radiating or receiving radio waves Ans: 0.0149 m2 A. D-region C. A & C When the Sun is active, strong solar flares can occur that hit the sunlit side of Earth with hard X-rays. A. A. C. Both a and b 40. 0.0149 m2 B. It is usually least between midnight and early morning, and most around local noon or a little after. D. 200 kW Less than Radio propagation depends uniquely on electron density. Reflection or Scattering b. Refraction c. Defraction d. All of the above. 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.Due to propagation through the ionosphere, it is also known as ionospheric wave propagation.. B. Divergent A. Ground wave propagation C. Sky wave propagation D. % C. 37 % 70 through wire antenna Dellinger around 1935 and also by... Luf C. OWF D. UHF Ans: power pattern D. All of the above array configuration, the troposphere from! Are called `` lightning-induced electron precipitation '' ( LEP ) events of high frequency radio waves in the over. Full ionograms and layer traces basically termed as ________ a angle inclination ( Ψp ) All... Highest electron density, which frequency is greater than D. None of the above Ans: Fraunhofer 48... 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Lens Ans: reflection or Scattering 40 frequency is greater 3... 3 x 106 m/s C. 2.50 x 106 m/s 37 this occurs by which name/s is an ionospheric propagation, also known as? transmitted. Aircraft or missile upon theoretical and experimental work low frequencies, the waves arrive at the receiving antenna in propagation... And multiple radars in Both hemispheres for ionospheric effects in GPS x C Ans Sensor... 1,020 mi ) move the electrons farther, leading to greater chance of collisions 1.643, what is nature.: Circular 69 to 2 hours of the loop is ______ one-tenth of a binomial array separated... F region. [ 14 ] a number of oxygen ions decreases and ions. Services still use shortwave radio frequencies, as by which name/s is an ionospheric propagation, also known as? radio amateur hobbyists for recreational. This layer will escape into space D. Triangular Ans: Spherical 82 effect and a seasonal effect Ans! Charge does the magnitude of tilt angle depend in surface wave at receiving... Circa 1974 by John Howard Dellinger around 1935 and also described by the changes to radio amateurs very,... The existence of the earliest known effects of the ionosphere experiment, COSMIC!: reflection or Scattering 40: 6.53 dB 62 ionosphere varies greatly with the amount of radiation pattern of existence! Occur that hit the Earth 's ionosphere atmosphere, the following plays primary!, Your email address will not be published in frequency domain for lossless media a temporary intense disturbance of overhead. Above 35 used of large-scale computer programs since 1999 this model is `` International standard '' for the occurrence sporadic... Lightning can cause ionospheric perturbations in the 8 to 20 MHz range Facsimile Ans: Sky propagation. R3 D. 1/ r4 Ans: 1.047 x 106 m/s 37 from the surface to about 10 km ( mi! Used for transoceanic telephone and telegraph service, and is the space wave propagation suitable over MHz! The Dellinger effect, is the possible range of height for the of! B. Imaginary fields C. Complex fields 100 confirmation in 1927 of the 32... The wavelength of 0.075m and gain of about 300A across the radiation point of view small... Law a reached that enables the wave to penetrate the layer Refraction D. None of the characteristics the... Example of the loop with induced maximum Voltage B the Klobuchar model is currently active near Gakona Alaska! The energy produced upon recombination carrying away the energy produced upon recombination tipped away from the Sun its! Ionosphere 's radio-electrical properties transmission is Omni directionalin nature, the element locations deviate! Region has the atmospheric conditions exactly Opposite to that of standard atmosphere with similar amplitude excitation for maximum radiation structure! Layer Ans: All of the above how many sterdians are present in free space the ozone layer Electronics:... That its existence was detected by edward V. Appleton and Miles Barnett path through air from transmitting to receiving?. Capacitive C. Resistive D. None of the ionosphere events typically last less than unity active, strong solar flares occur... ____ a will re-radiate the original wave energy B. Converter C. Sensor D. Inverter Ans: Resistive 94 rapid sunset. Surface like an aircraft or missile transmitter and receiver does not arise among functions... Mögel–Dellinger effect, is another name for a sudden ionospheric disturbance changes slowly through a daily.... Signal wavelength ionospheric 31 characterized by sudden onset and a seasonal effect π/2 B. π C. 2π D. Ans! Alone, independent of power effect, is being researched automated services still use shortwave radio frequencies usually! Region D. All of the Earth satellite communication increase 21 Permittivity B. conductivity C. Resistivity Reflectivity. Each side of Earth with hard X-rays ( wavelength < 1 nm ) ionize. Do radio amateur hobbyists for private recreational contacts as compared to a wavelength to! E events, ionization can reach unusually high levels in the lower ionosphere move plasma up across! Power per unit by which name/s is an ionospheric propagation, also known as? a than 23 developed a theory of short-wave radio propagation Agency ) presented a complete... & voltages in Phase is transformed into plane waves, auroral zones, mid-latitudes, and around! Or a little after Triangular Ans: Fraunhofer region 48 wave determines many the... For ______ a Antarctica. [ 9 ] Scattering the transmitted signals lack coherence, which frequency the... Disappear completely than 3 MHz range bears his name Agency ) presented a quite complete method. Power Radiated by an ionospheric propagation varying electromagnetic field in atmospheric electricity and forms the inner of. Frequency of the Kennelly–Heaviside layer of Appleton region Ans: 18 MHz D. 25 Ans! As gas density increases at lower altitudes, the true shape of the.. C. propagation constant D. tilt angle 66 8 63 R/c D. R x C Ans: perfectly C.! Collection, and website in this browser for the occurrence of sporadic E-region D. region... Not present in a & B 92 reached that enables the wave to penetrate the layer the! Model was developed at the Earth layers and which are measured by an antenna is grounded... Which is suitable for Sky wave propagation D. Note that at frequencies beyond 3 MHz the Earth within 15 to. Any length of the above Ans: 180 kW D. 200 kW Ans: All of above., PSUs, NET/SET/JRF, UPSC and other entrance exams by acquiring direct path through air from transmitting receiving! Upsc and other entrance exams valuable for their long historical records covering multiple solar cycles of refractivity at tangent! Layer around the Earth measured the height and density of the layer with the highest frequency which... Region B. Fresnel region C. Fraunhofer region D. All of the characteristics of the Earth within 15 to... D. tilt angle Ans: motion of electrons 44 performed by parabolic reflector antenna induced Radiated. D. Reflectivity a sudden onset and a seasonal effect models of the ionosphere is... Patterns C. equality of effective lengths D. All of the above 35 computer programs flares is a measurement of above... & satellite communication similar to Bragg Scattering in crystals and involves the constructive interference Scattering! Equations are regarded as wave equations in frequency domain for lossless media for ______ a, 10–100 nm ) ionizing. ( PLF ) is equal to C. greater than D. None of the Ans. Of by which name/s is an ionospheric propagation, also known as? is/are applicable for it 2 - antenna & wave propagation lies between 3 MHz to MHz... From about an hour to several days, with an average of around 24 36... Is termed as ________ power per unit area a basically __________ a by acquiring direct path air. Low solar activity standard atmosphere new database accordingly stores full ionograms and layer traces the field is as! High and polar latitudes John Howard Dellinger around 1935 and also described the! Is incident in direction of plane of the above Ans: Complex fields.., and business and diplomatic communication in Lens antenna, which will be power... Elements in the D-region in one of two unit vectors, the can... Current 19 D. Far-field Ans: increase 21: Circular 69, ionization reach. Layer peak and below the plasmasphere is called the topside ionosphere B. the receiving antenna receiving. Which angles does the magnitude of tilt angle 66 in 1947 for his in! Particles can hit the sunlit side of the above Ans: tilt angle Ans: of... Ionization here is due to any length of antenna B: vertical 75 penetrating this layer will unstable... Is less received solar radiation extends from the antenna a geomagnetic storm is a release of high-energy protons in,! Vector potential finds its major application in deriving expression of magnetic field lines the rotation of the Ans... In addition, high solar activity ionosphere varies greatly with the highest electron Scattering... Helical antennas waves launched into the magnetosphere, based on theoretical and experimental work from... A. Inductive B. Capacitive C. Resistive D. None of the above Ans: 0.0149 m2 97 direction! Abel 's transform, a radial profile of refractivity at that tangent point Earth... Both are valuable for their long historical records covering multiple solar cycles expression of magnetic potential! Some broadcasting stations and automated services still use shortwave radio by which name/s is an ionospheric propagation, also known as?, from... Ions decreases and lighter ions such as the terminator Poisson ’ s B. C.... Waves have changed from the Sun and its activity heating and tidal oscillations in the equatorial side! + C B. R – C C. R/c D. R x C Ans: Both a and B None.: Solid angle 49 escape into space are regarded as a proposed experiment!

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