NEETS_v10_WaveProp_Q___A

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1. Wave Propagation .................................................................................................... 1-1

Q1. What is propagation?A1. Propagation means spreading out.

Q2. How is a wave defined as it applies to wave propagation?

A2. A wave is a disturbance which moves through a medium.

Q3. What is wave motion?A3. A means of transferring energy from one place to another.

Q4. What are some examples of wave motion?

A4. Sound waves, light waves, radio waves, heat waves, water waves.

Q5. What type of wave motion is represented by the motion of water?A5. Transverse waves.

Q6. What are some examples of transverse waves?

A6. Radio waves, light waves, and heat waves.

Q7. What example of a longitudinal wave was given in the text?A7. A sound wave.

Q8. What are the three requirements for a wave to be propagated?A8. A source, medium, and detector (receiver).

Q9. What is a cycle?A9. A sequence of events, such as the positive and negative alternation of electrical current.

A10. The space occupied by one cycle of a radio wave at any given instant.

Q11. What is the law of reflection?A11. The law of reflection states: The angle of incidence is equal to the angle of reflection.

Q12. When a wave is reflected from a surface, energy is transferred. When is the transfer of

energy greatest?A12. When the incident wave is nearly parallel with the surface.

Q13. When is the transfer of energy minimum?

A13. When the incident wave is perpendicular to the surface. Also a dull (or black) surfacereflects very

little regardless of the angle.

Q14. A refracted wave occurs when a wave passes from one medium into another medium. Whatdetermines the angle of refraction?

A14. The density of the two mediums, and the velocity of the waves.

Q15. The apparent change in frequency or pitch because of motion is explained by what effect?A15. The Doppler effect.


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Q16. What term describes sounds capable of being heard by the human ear?A16. Sonics.

Q17. Are all sounds audible to the human ear? Why?A17. No. The average human ear cannot hear all sounds in the infrasonic and ultrasonic regions.

Q18. Sound waves transmitted from a source are sometimes weak when they reach the detector.What instrument is needed to boost the weak signal?

A18. An amplifier.

Q19. What are the three basic requirements for sound?A19. A source, medium, and detector (receiver).

Q20. What are the two general groups of sound?A20. Noise and tones.

Q21. What are the three basic characteristics of sound?A21. Pitch, intensity, and quality.

Q22. What is the normal audible range of the human ear?A22. 20 Hz to 20 kHz.

Q23. What is intensity as it pertains to sound?A23. The amount of energy transmitted from a source.

Q24. What characteristic of sound enables a person to distinguish one musical instrument from

another, if they are all playing the same note?A24. Quality.

Q25. How does density and temperature affect the velocity of sound?

A25. Velocity increases as density decreases and temperature increases.

Q26. What term is used in describing the science of sound?A26. Acoustics.

Q27. A sound wave that is reflected back toward the source is known as what type of sound?

A27. Echo.

Q28. What is the term for multiple reflections of sound waves?A28. Reverberation.

Q29. A cavity that vibrates at its natural frequency produces a louder sound than at other

frequencies. What term is used to describe this phenomenon?A29. Resonance.

Q30. What do we call a disturbance that distracts or distorts the quality of sound?

A30. Noise.

Q31. What are three means of producing light?A31. Mechanical, electrical, and chemical.


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Q32. What is the smallest unit of radiant energy?A32. A photon.

Q33. What unit is used to measure the different wavelengths of light?A33. Angstrom unit.

Q34. What are the three primary colors of light?A34. Red, green and blue.

MGA WALANG SAGOT SA NEETSQ35. What are the three secondary colors of light?

Q36. White light falls upon a dull, rough, dark-brown object. Will the light primarily be reflected,

diffused, or absorbed by the object?Q37. What color will be emitted by a dull, rough, black object when white light falls upon it?

Q38. A substance that transmits light but through which an object cannot be seen clearly is known as what kind of substance?

Q39. At what speed does light travel?

Q40. A light wave enters a sheet of glass at a perfect right angle to the surface. Is the majority of the wave reflected, refracted,

transmitted, or absorbed?Q41. When light strikes a piece of white paper, the light is reflected in all directions. What do we call this scattering of light?

Q42. What three examples of electromagnetic energy are mentioned in the text?

Q43. What is the main difference between the bulk of the electromagnetic spectrum and the visual

spectrum?

Q44. What are the two components (fields) that make up the electromagnetic wave?Q45. What do we call a conductor (or set of conductors) that radiates electromagnetic energy into space?

Q46. What do we call the field that is created between two rods when a voltage is applied to them?

Q47. When current flows through a conductor, a field is created around the conductor. What do we call this field?

Q48. An induction field is created around a conductor when current flows through it. What do we call the field that detaches itself

from the conductor and travels through space?

2. Radio Wave Propagation.......................................................................................... 2-1

Q1. Which two composite fields (composed of E and H fields) are associatedwith every antenna?

A1. Induction field and radiation field.

Q2. What composite field (composed of E and H fields) is found stored in theantenna?

A2. Induction field.

Q3. What composite field (composed of E and H fields) is propagated intofree space?

A3. Radiation field.

Q4. What is the term used to describe the basic frequency of a radio wave?A4. Fundamental frequency.

Q5. What is the term used to describe a whole number multiple of the basicfrequency of a radio wave?

A5. Harmonic frequency or harmonics.

Q6. It is known that WWV operates on a frequency of 10 megahertz. What isthe wavelength of WWV?

A6. 30 meters.


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Q7. A station is known to operate at 60-meters. What is the frequency of theunknown station?

A7. 5 megahertz.

Q8. If a transmitting antenna is placed close to the ground, how should theantenna be polarized to give the greatest signal strength?

A8. Vertically polarized.

Q9. In the right-hand rule for propagation, the thumb points in the directionof the E field and the forefinger points in the direction of the H field. In whatdirection does the middle finger point?

A9. Direction of wave propagation.

Q10. What is one of the major reasons for the fading of radio waves whichhave been reflected from a surface?

A10. Shifting in the phase relationships of the wave.

Q11. What are the three layers of the atmosphere?

A11. Troposphere, stratosphere, and ionosphere.

Q12. Which layer of the atmosphere has relatively little effect on radiowaves?

A12. Stratosphere.

Q13. What is the determining factor in classifying whether a radio wave is aground wave or a space wave?

A13. Whether the component of the wave is travelling along the surface orover the surface of the earth.

Q14. What is the best type of surface or terrain to use for radio wave

transmission?A14. Radio horizon is about 1/3 farther.

Q15. What is the primary difference between the radio horizon and thenatural horizon?

A15. Sea water.

Q16. What three factors must be considered in the transmission of a surfacewave to reduce attenuation?

A16. (a) electrical properties of the terrain (b) frequency (c) polarization ofthe antenna

Q17. What causes ionization to occur in the ionosphere?A17. High energy ultraviolet light waves from the sun.

Q18. How are the four distinct layers of the ionosphere designated?A18. D, E, F1, and F2 layers.

Q19. What is the height of the individual layers of the ionosphere?A19. D layer is 30-55 miles, E layer 55-90 miles, and F layers are 90-240miles.


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Q20. What factor determines whether a radio wave is reflected or refractedby the ionosphere?

A20. Thickness of ionized layer.

Q21. There is a maximum frequency at which vertically transmitted radio

waves can be refracted back to Earth. What is this maximum frequencycalled?

A21. Critical frequency.

Q22. What three main factors determine the amount of refraction in theionosphere?

A22. (a) density of ionization of the layer (b) frequency (c) angle at which itenters the layer

Q23. What is the skip zone of a radio wave?A23. A zone of silence between the ground wave and sky wave where thereis no reception.

Q24. Where does the greatest amount of ionospheric absorption occur in theionosphere?

A24. Where ionization density is greatest.

Q25. What is meant by the term "multipath"?A25. A term used to describe the multiple pattern a radio wave may follow.

Q26. When a wide band of frequencies is transmitted simultaneously, eachfrequency will vary in the amount of fading. What is this variable fadingcalled?

A26. Selective fading.

Q27. What are the two main sources of emi with which radio waves mustcompete?

A27. Natural and man-made interference.

Q28. Thunderstorms, snowstorms, cosmic sources, the sun, etc., are a fewexamples of emi sources. What type of emi comes from these sources?

A28. Natural.

Q29. Motors, switches, voltage regulators, generators, etc., are a fewexamples of emi sources. What type of emi comes from these sources?

A29. Man-made.

Q30. What are three ways of controlling the amount of transmitter-generatedemi?

A30. (a) filtering and shielding of the transmitter (b) limiting bandwidth (c)cutting the antenna to the correct frequency

Q31. What are three ways of controlling radiated emi during transmission?


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A31. (a) physical separation of the antenna (b) limiting bandwidth of theantenna (c) use of directional antennas

Q32. What are the two general types of variations in the ionosphere?A32. Regular and irregular variations.

Q33. What is the main difference between these two types of variations?A33. Regular variations can be predicted but irregular variations areunpredictable.

Q34. What are the four main classes of regular variation which affect theextent of ionization in the ionosphere?

A34. Daily, seasonal, 11-year, and 27-days variation.

Q35. What are the three more common types of irregular variations in theionosphere?

A35. Sporadic E, sudden disturbances, and ionospheric storms.

Q36. What do the letters muf, luf, and fot stand for?A36. Muf is maximum usable frequency. Luf is lowest usable frequency. Fot iscommonly known as optimum working frequency.

Q37. When is muf at its highest and why?A37. Muf is highest around noon. Ultraviolet light waves from the sun aremost intense.

Q38. What happens to the radio wave if the luf is too low?A38. When luf is too low it is absorbed and is too weak for reception.

Q39. What are some disadvantages of operating transmitters at or near the

luf?A39. Signal-to-noise ratio is low and the probability of multipath propagationis greater.

Q40. What are some disadvantages of operating a transmitter at or near themuf?

A40. Frequent signal fading and dropouts.

Q41. What is fot?A41. Fot is the most practical operating frequency that can be relied on toavoid problems of multipath, absorbtion, and noise.

Q42. How do raindrops affect radio waves?A42. They can cause attenuation by scattering.

Q43. How does fog affect radio waves at frequencies above 2 gigahertz?A43. It can cause attenuation by absorbtion.

Q44. How is the term "temperature inversion" used when referring to radiowaves?


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A44. It is a condition where layers of warm air are formed above layers ofcool air.

Q45. How does temperature inversion affect radio transmission?A45. It can cause vhf and uhf transmission to be propagated far beyondnormal line-of-sight distances.

Q46. In what layer of the atmosphere does virtually all weather phenomenaoccur?

A46. Troposphere.

Q47. Which radio frequency bands use the tropospheric scattering principlefor propagation of radio waves?

A47. Vhf and above.

Q48. Where is the tropospheric region that contributes most strongly totropospheric scatter propagation?

A48. Near the mid-point between the transmitting and receiving antennas,

just above the radio horizon.

3. Principles of Transmission Lines ............................................................................. 3-1

Q1. What connecting link is used to transfer energy from a radio transmitter to its antenna

located on the mast of a ship?

A1. Transmission line.

Q2. What term is used for the end of the transmission line that is connected to a transmitter?

A2. Input end, generator end, transmitter end, sending end, and source.

Q3. What term is used for the end of the transmission line that is connected to an antenna?A3. Output end, receiving end, load end and sink.

Q4. List the five types of transmission lines in use today.

A4. Parallel two-wire, twisted pair, shielded pair, coaxial line and waveguide.

Q5. Name two of the three described uses of a two-wire open line.

A5. Power lines, rural telephone lines, and telegraph lines.

Q6. What are the two primary disadvantages of a two-wire open line?A6. High radiation losses and noise pickup.

Q7. What type of transmission line is often used to connect a television set to its antenna?A7. Twin lead.

Q8. What is the primary advantage of the shielded pair?


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A8. The conductors are balanced to ground.

Q9. What are the two types of coaxial lines in use today?A9. Air coaxial (rigid) and solid coaxial (flexible).

Q10. What is the chief advantage of the air coaxial line?

A10. The ability to minimize radiation losses.

Q11. List the three disadvantages of the air coaxial line.A11. Expensive to construct, must be kept dry, and high frequency losses limit the practical

length of the line.

Q12. List the two common types of waveguides in use today.A12. Cylindrical and rectangular.

Q13. What are the three types of line losses associated with transmission lines?

A13. Copper, dielectric, and radiation.

Q14. Losses caused by skin effect and the I2R (power) loss are classified as what type of loss?A14. Copper losses.

Q15. What types of losses cause the dielectric material between the conductors to be heated?

A15. Dielectric losses.

Q16. What must the physical length of a transmission line be if it will be operated at 15,000,000Hz?

Q17. What are two of the three physical factors that determine the values of capacitance andinductance of a transmission line?

A17. (1) Type of line used, (2) dielectric in the line, and (3) length of line.

Q18. A transmission line is said to have distributed constants of inductance, capacitance, andresistance along the line. What units of measurement are used to express these constants?

A18. Inductance is expressed in microhenrys per unit length, capacitance is expressed inpicofarads per unit length, and resistance is expressed in ohms per unit length.

Q19. Describe the leakage current in a transmission line and in what unit it is expressed.A19. The small amount of current that flows through the dielectric between two wires of atransmission line and is expressed in micromhos per unit length.

Q20. All the power sent down a transmission line from a transmitter can be transferred to an

antenna under what optimum conditions?A20. When the characteristic impedance of the transmission line and the load impedance are

equal.

Q21. What symbol is used to designate the characteristic impedance of a line, and what twovariables does it compare?

A21. Z0 and it is the ratio of E to I at every point along the line.

Q22. What is the range of the characteristic impedance of lines used in actual practice?


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A22. Between 50 and 600 ohms.

Q23. Two types of waves are formed on a transmission line. What names are given to thesewaves?A23. Incident waves from generator to load. Reflected waves from load back to generator.

Q25. On an open-ended transmission line, the voltage is always zero at what distance from eachend of the line?

A25. One-fourth the distance from each end of the line.

Q26. A nonresonant line is a line that has no standing waves of current and voltage on it and isconsidered to be flat. Why is this true?

A26. The load impedance of such a line is equal to Z0.

Q27. On an open line, the voltage and impedance are maximum at what points on the line?

Q28. At what point on an open-circuited rf line do voltage peaks occur?A28. At 1/2 wavelength from the end and at every 1/2 wavelength along the line.

Q29. What is the square of the voltage standing-wave ratio called?A29. Power standing-wave ratio (pswr).

Q30. What does vswr measure?

A30. The existence of voltage variations on a line.

4. Antennas ................................................................................................................... 4-1

Q1. What are the two basic classifications of antennas?A1. Half-wave (Hertz) and quarter-wave (Marconi).

Q2. What are the three parts of a complete antenna system?A2. Coupling device, feeder, and antenna.

Q3. What three factors determine the type, size, and shape of an antenna?A3. Frequency of operation of the transmitter, amount of power to beradiated, and general direction of the receiving set.

Q4. If a wave travels exactly the length of an antenna from one end to theother and back during the period of 1 cycle, what is the length of theantenna?

A4. One-half the wavelength.

Q5. What is the term used to identify the points of high current and highvoltage on an antenna?

A5. Current and voltage loops.

Q6. What is the term used to identify the points of minimum current andminimum voltage on an antenna?

A6. Current and voltage nodes.


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Q7. The various properties of a transmitting antenna can apply equally to thesame antenna when it is used as a receiving antenna. What term is used forthis property?

A7. Reciprocity of antennas.

Q8. The direction of what field is used to designate the polarization of a

wave?A8. Electric (E) field.

Q9. If a wave's electric lines of force rotate through 360 degrees with everycycle of rf energy, what is the polarization of this wave?

A9. Circular polarization.

Q10. What type of polarization should be used at medium and lowfrequencies?

A10. Vertical polarization.

Q11. What is an advantage of using horizontal polarization at high

frequencies?A11. Less interference is experienced by man-made noise sources.

Q12. What type of polarization should be used if an antenna is mounted on amoving vehicle at frequencies below 50 megahertz?

A12. Vertical polarization.

Q13. What is the radiation resistance of a half-wave antenna in free space?A13. 73 ohms.

Q14. A radiating source that radiates energy stronger in one direction thananother is known as what type of radiator?

A14. Anisotropic radiator.

Q15. A radiating source that radiates energy equally in all directions is knownas what type of radiator?

A15. Isotropic radiator.

Q16. A flashlight is an example of what type of radiator?A16. Anisotropic radiator.

Q17. What terms are often used to describe basic half-wave antennas?A17. Dipole, doublet and Hertz.

Q18. If a basic half-wave antenna is mounted vertically, what type ofradiation pattern will be produced?

A18. Nondirectional.

Q19. In which plane will the half-wave antenna be operating if it is mountedhorizontally?

A19. Vertical plane.


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Q20. Since the radiation pattern of a dipole is similar to that of a doublet,what will happen to the pattern if the length of the doublet is increased?

A20. The pattern would flatten.

Q21. What is the simplest method of feeding power to the half-waveantenna?

A21. To connect one end through a capacitor to the final output stage of thetransmitter.

Q22. What is the radiation pattern of a quarter-wave antenna?A22. A circular radiation pattern in the horizontal plane, or same as a halfwave.

Q23. Describe the physical arrangement of a ground screen.A23. It is composed of a series of conductors arranged in a radial pattern andburied 1 to 2 feet belowthe ground.

Q24. What is the difference in the amount of impedance between a three-wire dipole and a simple center-fed dipole?

A24. Nine times the feed-point impedance.

Q25. Which has a wider frequency range, a simple dipole or a folded dipole?A25. Folded dipole.

Q26. What is the purpose of antenna stubs?A26. To produce desired phase relationship between connected elements.

Q27. What is the primary difference between the major and minor lobes of aradiation pattern?

A27. Major lobes have the greatest amount of radiation.

Q28. What is the maximum number of elements ordinarily used in a collineararray?

A28. Four.

Q29. Why is the number of elements used in a collinear array limited?A29. As more elements are added, an unbalanced condition in the systemoccurs which impairs efficiency.

Q30. How can the frequency range of a collinear array be increased?A30. By increasing the lengths of the elements of the array.

Q31. How is directivity of a collinear array affected when the number ofelements is increased?

A31. Directivity increases.

Q32. What is the primary cause of broadside arrays losing efficiency whennot operating at their designed frequency?

A32. Lower radiation resistance.


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Q33. When more than two elements are used in a broadside array, how arethe elements arranged?

A33. Parallel and in the same plane.

Q34. As the spacing between elements in a broadside array increases, whatis the effect on the major lobes?

A34. They sharpen.

Q35. What are some disadvantages of the end-fire array?A35. Extremely low radiation resistance, confined to one frequency, andaffected by atmospheric conditions.

Q36. Where does the major lobe in the end-fire array occur?A36. Along the major axis

Q37. To maintain the required balance of phase relationships and criticalfeeding, how must the end-fire array be constructed?

A37. Symmetrically.

Q38. What two factors determine the directivity pattern of the parasiticarray?

A38. Length of the parasitic element (tuning) and spacing between theparasitic and driven elements.

Q39. What two main advantages of a parasitic array can be obtained bycombining a reflector and a director with the driven element?

A39. Increased gain and directivity.

Q40. The parasitic array can be rotated to receive or transmit in differentdirections. What is the name given to such an antenna?

A40. Rotary array.

Q41. What are the disadvantages of the parasitic array?A41. Their adjustment is critical and they do not operate over a widefrequency range.

Q42. What is the advantage of adding parasitic elements to a Yagi array?A42. Increased gain.

Q43. The Yagi antenna is an example of what type of array?A43. Multielement parasitic array.

Q44. To radiate power efficiently, a long-wire antenna must have whatminimum overall length?

A44. One-half wavelength.

Q45. What is another name for the Beverage antenna?A45. Wave antenna.

Q46. What is the polarity of the currents that feed the V antenna?A46. Opposite.


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Q47. What is the main disadvantage of the rhombic antenna?A47. It requires a large antenna site.

Q48. What is the primary reason for the development of the turnstileantenna?

A48. For omnidirectional vhf communications.

NEETS_v10_WaveProp_Q___A

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