IONIZATION—The process of upsetting electrical neutrality.
ISOTROPIC RADIATION—The radiation of energy equally in all directions.
LEAKAGE CURRENT—The small amount of current that flows between the conductors of a transmission line through the dielectric.
LIGHT RAYS—Straight lines that represent light waves emitting from a source.
LOAD END—See OUTPUT END.
LOADING—See LUMPED-IMPEDANCE TUNING.
LOBE—An area of a radiation pattern plotted on a polar-coordinate graph that represents maximum radiation.
LONG-WIRE ANTENNA—An antenna that is a wavelength or more long at its operating frequency.
LONGITUDINAL WAVES—Waves in which the disturbance (back and forth motion) takes place in the direction of propagation. Sometimes called compression waves.
LOOP—The curves of a standing wave or antenna that represent amplitude of current or voltage.
AI-6
LOWEST USABLE FREQUENCY—The minimum operating frequency that can be used for communications between two points.
LUMPED CONSTANTS—The properties of inductance, capacitance, and resistance in a transmission line.
LUMPED-IMPEDANCE TUNING—The insertion of an inductor or capacitor in series with an antenna to lengthen or shorten the antenna electrically.
MAGNETIC (H) FIELD—The field produced when current flows through a conductor or antenna. MAJOR LOBE—The lobe in which the greatest amount of radiation occurs.
MARCONI ANTENNA—A quarter-wave antenna oriented perpendicular to the earth and operated with one end grounded.
MAXIMUM USABLE FREQUENCY— Maximum frequency that can be used for communications between two locations for a given time of day and a given angle of incidence.
MEDIUM—The substance through which a wave travels from one point to the next. Air, water, wood, etc., are examples of a medium.
MINOR LOBE—The lobe in which the radiation intensity is less than a major lobe. MULTIELEMENT ARRAY—An array consisting of one or more arrays and classified as to directivity.
MULTIELEMENT PARASITIC ARRAY— An array that contains two or more parasitic elements and a driven element.
MULTIPATH—The multiple paths a radio wave may follow between transmitter and receiver.
NATURAL HORIZON—The line-of-sight horizon.
NEGATIVE ALTERNATION—The portion of a sine wave below the reference line.
NODE—The fixed minimum points of voltage or current on a standing wave or antenna.
NOISE (OF SOUND)—An unwanted disturbance caused by spurious waves that originate from man- made or natural sources.
NONDIRECTIONAL—See OMNIDIRECTIONAL.
NONLUMINOUS BODIES—Objects that either reflect or diffuse light that falls upon them. NONRESONANT LINE—A transmission line that has no standing waves of current or voltage.
NORMAL—The imaginary line perpendicular to the point at which the incident wave strikes the reflecting surface. Also called the perpendicular.
NULL—On a polar-coordinate graph, the area that represents minimum or 0 radiation.
OMNIDIRECTIONAL—Transmitting in all directions.
OPAQUE—A type of substance that does not transmit any light rays. OPEN-ENDED LINE—A transmission line that has an infinitely large terminating impedance.
AI-7
OPTIMUM WORKING FREQUENCY—The most practical operating frequency that can be used with the least amount of problems; roughly 85 percent of the maximum usable frequency.
ORIGIN—The point on a graph where the vertical and horizontal axes cross each other.
OUTPUT END—The end of a transmission line that is opposite the source.
OUTPUT IMPEDANCE—The impedance presented to the load by the transmission line and its source.
PARALLEL RESONANT CIRCUIT—A circuit that acts as a high impedance at resonance.
PARALLEL-WIRE—A type of transmission line consisting of two parallel wires.
PARASITIC ARRAY—An array that has one or more parasitic elements.
PARASITIC ELEMENT—The passive element of an antenna array that is connected to neither the transmission line nor the driven element.
PERIOD—The amount of time required for completion of one full cycle.
PITCH—A term used to describe the frequency of a sound heard by the human ear.
PLANE OF POLARIZATION—The plane (vertical or horizontal) with respect to the earth in which the E field propagates.
POINT OF ZERO DISPLACEMENT—See REFERENCE LINE.
POLAR-COORDINATE GRAPH—A graph whose axes consist of a series of circles with a common center and a rotating radius extending from the center of the concentric circles.
POSITIVE ALTERNATION—The portion of a sine wave above the reference line.
POWER LOSS—The heat loss in a conductor as current flows through it.
POWER STANDING-WAVE RATIO (PSWR)—The ratio of the square of the maximum and minimum voltages of a transmission line.
PRIMARY COLORS (OF LIGHT)—The three primary colors of light (red, green, and blue), from which all other colors may be derived.
PRISM—A triangular-shaped glass that refracts and disperses light waves into component wavelengths.
PROPAGATION—Waves traveling through a medium.
QUALITY (OF SOUND)—The factor that distinguishes tones of pitch and loudness. QUARTER-WAVE ANTENNA—Same as the Marconi antenna. RADIATION FIELD—The electromagnetic field that detaches itself from an antenna and travels
through space.
RADIATION LOSSES—The losses that occur when magnetic lines of force about a conductor are projected into space as radiation and are not returned to the conductor as the cycle alternates.
RADIATION PATTERN—A plot of the radiated energy from an antenna.
AI-8
RADIATION RESISTANCE—The resistance, which if inserted in place of an antenna, would consume the same amount of power as that radiated by the antenna.
RADIO FREQUENCIES—Electromagnetic frequencies that fall between 3 kilohertz and 300 gigahertz and are used for radio communications.
RADIO HORIZON—The boundary beyond the natural horizon in which radio waves cannot be propagated over the earth's surface.
RADIO WAVE—(1) A form of radiant energy that can neither be seen nor felt. (2) An electromagnetic wave generated by a transmitter.
RAREFIED WAVE—A longitudinal wave that has been expanded or rarefied (made less dense) as it moves away from the source.
RECEIVER—The object that responds to a wave or disturbance. Same as detector. RECEIVING ANTENNA—The device used to pick up an rf signal from space.
RECEIVING END—See OUTPUT END.
RECIPROCITY—The property of interchangeability of the same antenna for transmitting and receiving.
RECTANGULAR-COORDINATE GRAPH—A graph in which straight-line axes (horizontal and vertical) are perpendicular.
REFERENCE LINE—The position a particle of matter would occupy if it were not disturbed by wave motion.
REFLECTED WAVE—(1) The wave that reflects back from a medium. (2) Waves traveling from the load back to the generator on a transmission line. (3) The wave moving back to the sending end of a transmission line after reflection has occurred.
REFLECTION WAVES—Waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter.
REFLECTOR—The parasitic element of an array that causes maximum energy radiation in a direction toward the driven element.
REFRACTION—The changing of direction as a wave leaves one medium and enters another medium of a different density.
RERADIATION—The reception and retransmission of radio waves caused by turbulence in the troposphere.
RESONANCE—The condition produced when the frequency of vibrations are the same as the natural frequency (of a cavity). The vibrations reinforce each other.
RESONANT LINE—A transmission line that has standing waves of current and voltage.
REST POSITION—See REFERENCE LINE.
REVERBERATION—The multiple reflections of sound waves.
AI-9
RHOMBIC ANTENNA—A diamond-shaped antenna used widely for long-distance, high-frequency transmission and reception.
RIGID COAXIAL LINE—A coxial line consisting of a central, insulated wire (inner conductor) mounted inside a tubular outer conductor.
SCATTER ANGLE—The angle at which the receiving antenna must be aimed to capture the scattered energy of tropospheric scatter.
SELF-INDUCTION—The phenomenon caused by the expanding and collapsing fields of an electron which encircles other electrons and retards the movement of the encircled electrons.
SELF-LUMINOUS BODIES—Objects that produce their own light. SENDING END—See INPUT END.
SERIES RESONANT CIRCUIT—A circuit that acts as a low impedance at resonance.
SHIELDED PAIR—A line consisting of parallel conductors separated from each other and surrounded by a solid dielectric.
SHORT-CIRCUITED LINE—A transmission line that has a terminating impedance equal to 0.
SINK—See OUTPUT END.
SKIN EFFECT—The flow of ac current near the surface of a conductor at rf frequencies.
SKIP DISTANCE—The distance from a transmitter to the point where the sky wave is first returned to earth.
SKIP ZONE—A zone of silence between the point where the ground wave becomes too weak for reception and the point where the sky wave is first returned to earth.
SKY WAVES—Radio waves reflected back to earth from the ionosphere.
SONIC—Pertaining to sounds capable of being heard by the human ear.
SOURCE—(1) The object that produces waves or disturbance. (2) The name given to the end of a two- wire transmission line that is connected to a source.
SPACE DIVERSITY—Reception of radio waves by two or more antennas spaced some distance apart.
SPACE WAVE—A radio wave that travels directly from the transmitter to the receiver and remains in the troposphere.
SPECTRUM—(1) The entire range of electromagnetic waves. (2) VISIBLE. The range of electromagnetic waves that stimulate the sense of sight. (3) ELECTROMAGNETIC. The entire range of electromagnetic waves arranged in order of their frequencies.
SPORADIC E LAYER—Irregular cloud-like patches of unusually high ionization. Often forms at heights near the normal E layer.
SPREADER—Insulator used with transmission lines and antennas to keep the parallel wires separated.
AI-10
STANDING WAVE—The distribution of voltage and current formed by the incident and reflected waves which have minimum and maximum points on a resultant wave that appears to stand still.
STANDING-WAVE RATIO (SWR)—The ratio of the maximum (voltage, current) to the minimum (voltage, current) of a transmission line. Measures the perfection of the termination of the line.
STRATOSPHERE—Located between the troposphere and the ionosphere. Has little effect on radio waves.
STUB—Short section of a transmission line used to match the impedance of a transmission line to an antenna. Can also be used to produce desired phase relationships between connected elements of an antenna.
SUDDEN IONOSPHERIC DISTURBANCE—An irregular ionospheric disturbance that can totally blank out hf radio communications.
SUPERSONIC—Speed greater than the speed of sound.
SURFACE WAVE—A radio wave that travels along the contours of the earth, thereby being highly attenuated.
TEMPERATURE INVERSION—The condition in which warm air is formed above a layer of cool air that is near the earth's surface.
THREE-ELEMENT ARRAY—An array with two parasitic elements (reflector and director) and a driven element.
TONES—Musical sounds.
TRANSLUCENT—A type of substance, such as frosted glass, through which some light rays can pass but through which objects cannot be seen clearly.
TRANSMISSION LINE—A device designed to guide electrical energy from one point to another.
TRANSMITTING ANTENNA—The device used to send the transmitted signal energy into space.
TRANSPARENT—A type of substance, such as glass, that transmits almost all of the light waves that fall upon it.
TRANSMISSION MEDIUMS—The various types of lines and waveguides used as transmission lines.
TRANSMITTER END—See INPUT END.
TRANSVERSE WAVE MOTION—The up and down motion of a wave as the wave moves outward.
TROPOSPHERE—The portion of the atmosphere closest to the earth's surface, where all weather phenomena take place.
TROPOSPHERIC SCATTER—The propagation of radio waves in the troposphere by means of scatter.
TROUGH (BOTTOM)—The peak of the negative alternation (maximum value below the line). TUNED LINE—Another name for the resonant line. This line uses tuning devices to eliminate the
reactance and to transfer maximum power from the source to the line.
AI-11
TURNSTILE ANTENNA—A type of antenna used in vhf communications that is omnidirectional and consists of two horizontal half-wave antennas mounted at right angles to each other in the same horizontal plane.
TWISTED PAIR—A line consisting of two insulated wires twisted together to form a flexible line without the use of spacers.
TWO-WIRE OPEN LINE—A parallel line consisting of two wires that are generally spaced from 2 to 6 inches apart by insulating spacers.
TWO-WIRE RIBBON (TWIN LEAD)—A parallel line similar to a two-wire open line except that uniform spacing is assured by embedding the two wires in a low-loss dielectric.
ULTRASONIC—Sounds above 20,000 hertz.
UNIDIRECTIONAL ARRAY—An array that radiates in only one general direction.
UNTUNED LINE—Another name for the flat or nonresonant line.
V ANTENNA—A bi-directional antenna, shaped like a V, which is widely used for communications.
VELOCITY—The rate at which a disturbance travels through a medium.
VERTICAL AXIS—On a graph, the straight line axis oriented from bottom to top.
VERTICAL PATTERN—The part of a radiation pattern that is radiated in the vertical plane.
VERTICALLY POLARIZED—Waves radiated with the E field component perpendicular to the earth's surface.
VOLTAGE-FEED METHOD—Same as END FEED METHOD.
VOLTAGE STANDING-WAVE RATIO (VSWR)—The ratio of maximum to minimum voltage of a transmission line.
WAVE ANTENNA—Same as BEVERAGE ANTENNA.
WAVE MOTION—A recurring disturbance advancing through space with or without the use of a physical medium.
WAVE TRAIN—A continuous series of waves with the same amplitude and wavelength.
WAVEFRONT—A small section of an expanding sphere of electromagnetic radiation, perpendicular to the direction of travel of the energy.
WAVEGUIDE—A hollow metal tube used as a transmission line to guide energy from one point to another.
WAVELENGTH—(1) The distance in space occupied by 1 cycle of a radio wave at any given instant. (2) The distance a disturbance travels during one period of vibration.
YAGI ANTENNA—A multielement parasitic array. Elements lie in the same plane as those of the end- fire array.
INDEX-1
INDEX-2
INDEX-3
V
Information: The text pages that you are to study are provided at the beginning of the assignment questions.
1
ASSIGNMENT 1 Textbook assignment: Chapter 1, “Wave Propagation,” pages 1-1 through 1-48.
1-1. What is the major advantage of the telegraph over earlier methods of communication?
1. Range 2. Speed 3. Security 4. Reliability
1-2. The spreading out of radio waves is referred to as propagation and is used in which of the following Navy equipment?
1. Detection 2. Communication 3. Radar and navigation 4. Each of the above
1-3. Radio-frequency waves CANNOT be seen for which of the following reasons?
1. Because radio-frequency energy is low powered
2. Because radio-frequency waves are below the sensitivity range of the human eye
3. Because the human eye detects only magnetic energy
4. Because radio-frequency waves are above the sensitivity range of the human eye
1-4. Radio waves travel at what speed?
1. Speed of sound 2. Speed of light 3. Speed of the Earth's rotation 4. Speed of the Earth's orbit around the
1-5. Which of the following types of energy CANNOT be seen, heard, or felt?
1. Radio waves 2. Sound waves 3. Heat waves 4. Light waves
1-6. A stone dropped into water creates a series of expanding circles on the surface of the water. This is an example of which of the following types of wave motion?
1. Transverse 2. Concentric 3. Longitudinal 4. Compression
1-7. A sound wave that moves back and forth in the direction of propagation is an example of which of the following types of wave motion?
1. Composite 2. Concentric 3. Transverse 4. Longitudinal
1-8. Which of the following terms is used for the vehicle through which a wave travels from point to point?
1. Medium 2. Source 3. Detector 4. Receiver
1-9. Which of the following is NOT an element necessary to propagate sound?
1. Medium 2. Source 3. Detector 4. Reference
2
1-10. If a wave has a velocity of 4,800 feet per second and a wave-length of 5 feet, what is the frequency of the wave?
1. 9.6 Hz 2. 96 Hz 3. 960 Hz 4. 9,600 Hz
IN ANSWERING QUESTIONS 1-11 THROUGH 1-15, REFER TO FIGURE 1-A.
1-11. The waveform in the figure is what type of wave?
1. Sine 2. Square 3. Sawtooth 4. Trapezoidal
1-12. The distance between which of the following points represents the completion of a full cycle of alternating current?
1. A to C 2. B to D 3. C to E 4. D to F
1-13. The distance between which of the following points represents a full wavelength?
1. A to D 2. A to E 3. D to E 4. E to F
1-14. What is the frequency of the wave?
1. 0.5 Hz 2. 2.5 Hz 3. 5.0 Hz 4. 7.5 Hz
1-15. What is the period of the wave?
1. 100 milliseconds 2. 200 milliseconds 3. 250 milliseconds 4. 500 milliseconds
IN ANSWERING QUESTIONS 1-16 THROUGH 1-19, REFER TO FIGURE 1-B.
1-16. What line in the figure indicates the incident wave?
1. A to B 2. B to E 3. C to B 4. D to H
1-17. Angle "x" is which of the following angles?
1. Normal 2. Incidence 3. Reflection 4. Refraction
3
1-18. Line E to F represents which of the following waves?
1. Normal 2. Incident 3. Refracted 4. Reflected
1-19. Line D to H represents which of the following references?
1. Normal 2. Perpendicular 3. Both 1 and 2 above 4. Reflected line
1-20. Which of the following statements about a wave is the law of reflection?
1. The angle of incidence is equal to the refracted wave
2. The angle of incidence is not equal to the refracted wave
3. The angle of incidence is equal to the angle of reflection
4. The angle of incidence is not equal to the angle of reflection
1-21. If a wave passes first through a dense medium and then through a less dense medium, which of the following angle- of-refraction conditions exists?
1. The angle of refraction is greater than the angle of incidence
2. The angle of refraction is less than the angle of incidence
3. The angle of refraction is equal to the angle of incidence
4. The wave will pass through in a straight line
1-22. The reception of an AM-band radio signal over mountains can be explained by which of the following principles of wave propagation?
1. Reflection 2. Refraction 3. Diffraction 4. Doppler effect
1-23. What wave propagation principle accounts for the apparent increase in frequency as a train whistle approaches and the apparent decrease in frequency as it moves away?
1. Refraction 2. Reflection 3. Diffraction 4. Doppler effect
1-24. Longitudinal wave disturbances that travel through a medium are known as what type of waves?
1. Air 2. Sound 3. Radio 4. Light
1-25. What are the three audible frequency ranges?
1. Subsonic, sonic, and supersonic 2. Infrasonic, sonic, and ultrasonic 3. Infrasonic, subsonic, and ultrasonic 4. Infrasonic, subsonic, and supersonic
1-26. If a bell is placed in a jar and the air in the jar is replaced with a gas of a higher density, what is the effect, if any, on the speed of the sound when the bell is rung?
1. The sound stops 2. The sound travels faster 3. The sound travels slower 4. The sound is not affected
1-27. Varying which of the following wave characteristics will cause the length of sound waves to vary?
1. Phase 2. Quality 3. Amplitude 4. Frequency
4
1-28. What are the three basic characteristics of sound?
1. Amplitude, intensity, and quality 2. Amplitude, pitch, and tone 3. Pitch, intensity, and quality 4. Pitch, frequency, and quality
1-29. If several musical instruments are playing the same note, you should be able to distinguish one instrument from another because of which of the following characteristics of sound?
1. Quality 2. Overtones 3. Frequency 4. Intensity
1-30. Through which of the following mediums will sound travel fastest, at the indicated temperature?
1. Air at 68º F 2. Lead at 20º C 3. Steel at 32º F 4. Steel at 20º C
1-31. In sound terminology, which of the following terms is the same as a wave reflection?
1. Echo 2. Image 3. Acoustics 4. Refraction
1-32. Multiple reflections of sound waves are referred to as
1. noise 2. acoustics 3. interference 4. reverberation
1-33. Two out-of-phase waves of the same frequency that are moving through the same medium are said to present which of the following types of interference?
1. Additive 2. Constructive 3. Both 1 and 2 above 4. Subtractive
1-34. A cavity that vibrates at its own natural frequency and produces a sound that is louder than at other frequencies is demonstrating which of the following sound characteristics?
1. Noise 2. Quality 3. Resonance 4. Reverberation
1-35. Energy in the form of light can be produced through which of the following means?
1. Chemical 2. Electrical 3. Mechanical 4. Each of the above
1-36. The scientist, J. C. Maxwell, developed the theory that small packets of electromagnetic energy called photons produce
1. sound 2. noise 3. echoes 4. light
1-37. A large volume of light radiating in a given direction is referred to as a
1. ray 2. beam 3. shaft 4. pencil
5
1-38. Which of the following units of measurement is/are used to measure very short wavelengths of light?
1. Angstrom ( � 2. Millimicron 3. Both 1 and 2 above 4. Millimeter
1-39. What are the primary colors of light?
1. Red, blue, and yellow 2. Red, blue, and green 3. Red, violet, and indigo 4. Blue, green, and violet
1-40. What are the secondary colors of light?
1. Orange, yellow, and blue-green 2. Magenta, yellow, and cyan 3. Purple, yellow, and black 4. Red, white, and blue
1-41. What causes sunlight to separate into different wavelengths and display a rainbow of colors when passed through a prism?
1. Refraction 2. Reflection 3. Dispersion 4. Diffraction
1-42. The sun, gas flames, and electric light filaments are visible because they are
1. opaque 2. transparent 3. nonluminous 4. self-luminous
1-43. Substances that transmit almost all of the light waves falling upon them possess which of the following properties?
1. Opaqueness 2. Transparence 3. Translucence 4. Self-lumination
1-44. Some substances are able to transmit light waves but objects cannot be seen through them. Which of the following properties does this statement describe?
1. Opaqueness 2. Transparence 3. Translucence 4. Self-lumination
1-45. The speed of light depends on the medium through which light travels. For which of the following reasons does light travel through empty space faster than through an object such as glass?
1. Space is less dense than glass 2. Space is more dense than glass 3. Glass reflects the light back to the
source 4. Glass refracts the light, causing the
1-46. If a light wave strikes a sheet of glass at a perpendicular angle, what is the effect, if any, on the light wave?
1. The wave is completely absorbed 2. The wave is reflected back toward the
source 3. The wave is refracted as it passes
through the glass 4. The wave is unchanged and continues
1-47. The amount of absorption of the light that strikes an object is determined by the object’s
1. color 2. purity 3. density 4. complexity
6
1-48. In a comparison of waves of light and sound as they travel from an air into water, how is the speed of (a) light waves and (b) sound waves affected?
1. (a) Increased (b) increased 2. (a) Increased (b) decreased 3. (a) Decreased (b) decreased 4. (a) Decreased (b) increased
1-49. Which of the following waves are NOT a form of electromagnetic energy?
1. Heat waves 2. Sound waves 3. Light waves 4. Radio waves
1-50. The electromagnetic spectrum represents the entire range of electromagnetic waves arranged in the order of their
1. color 2. frequency 3. visibility 4. application
1-51. Which of the following portions of the frequency spectrum contains the highest frequency?
1. X-ray 2. Radar 3. Light 4. Cosmic
1-52. Which of the following electronic devices is used to radiate and/or collect electromagnetic waves?
1. Antenna 2. Receiver 3. Transmitter 4. Transmission line
1-53. The electric field and magnetic field combine to form which of the following types of waves?
1. Spherical 2. Elliptical 3. Electromagnetic 4. Each of the above
1-54. The magnetic field radiated from an antenna is produced by what electrical property?
1. Voltage 2. Current 3. Reactance 4. Resistance
1-55. The electric field radiated from an antenna is produced by what electrical property?
1. Voltage 2. Current 3. Reactance 4. Resistance
1-56. Applying rf energy to the elements of an antenna results in what phase relationship between voltage and current?
1. Voltage lags current by 90 degrees 2. Voltage leads current by 90 degrees 3. Voltage and current are 180 degrees
out of phase 4. Voltage and current are in phase
1-57. What field exists close to the conductor of an antenna and carries the current?
1. Electric 2. Magnetic 3. Induction 4. Radiation
7
1-58. What field travels through space after being detached from the current-carrying rod of an antenna?
1. Electric 2. Magnetic 3. Induction 4. Radiation
1-59. Electric and magnetic fields on an antenna reach their maximum intensity at which of the following times?
1. When they are a full cycle apart 2. When they are three-quarter cycle
apart 3. When they are a half-cycle apart 4. When they are a quarter-cycle apart
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Textbook assignment: Chapter 2, “Radio Wave Propagation,” pages 2-1 through 2-47. _______________________________________________________________________________________
2-1. The induction field is made up of which of the following fields?
1. E field only 2. H field only 3. Both E and H fields
2-2. After the radiation field leaves an antenna, what is the relationship between the E and H fields with respect to (a) phase and (b) physical displacement in space?
1. (a) In phase (b) 90 degrees 2. (a) Out of phase (b) 90 degrees 3. (a) In phase (b) 180 degrees 4. (a) Out of phase (b) 180 degrees
2-3. What is the first harmonic of a radio wave that has a fundamental frequency of 2,000 kHz?
1. 6,000 kHz 2. 2,000 kHz 3. 3,000 kHz 4. 4,000 kHz
2-4. In a radio wave with a fundamental frequency of 1.5 kHz, which of the following frequencies is NOT a harmonic?
1. 6,000 kHz 2. 5,000 kHz 3. 3,000 kHz 4. 4,000 kHz
2-5. A radio wave with a frequency of 32 kHz is part of which of the following frequency bands?
1. The lf band 2. The mf band 3. The hf band 4. The vhf band
2-6. A frequency of 3.5 GHz falls into what rf band?
1. High 2. Very high 3. Super high 4. Extremely high
2-7. A radio wavelength expressed as 250 meters may also be expressed as how many feet?
1. 410 2. 820 3. 1,230 4. 1,640
2-8. An increase in the frequency of a radio wave will have what effect, if any, on the velocity of the radio wave?
1. Increase 2. Decrease 3. None
2-9. An increase in frequency of a radio wave will have what effect, if any, on the wavelength of the radio wave?
1. Increase 2. Decrease 3. None
2-10. What is the frequency, in kiloHertz, of a radio wave that is 40 meters long?
1. 75 2. 750 3. 7,500 4. 75,000
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2-11. What is the approximate wavelength, in feet, of a radio wave with a frequency of 5,000 kHz?
1. 197 feet 2. 1,970 feet 3. 19,700 feet 4. 197,000 feet
2-12. The polarity of a radio wave is determined by the orientation of (a) what moving field with respect to (b) what reference?
1. (a) Electric (b) earth 2. (a) Electric (b) antenna 3. (a) Magnetic (b) antenna 4. (a) Magneti (b) earth
2-13. Energy radiated from an antenna is considered horizontally polarized under which of the following conditions?
1. If the wavefront is in the horizontal plane
2. If the magnetic field is in the horizontal plane
3. If the electric field is in the horizontal plane
4. If the induction field is in the horizontal plane
2-14. The ability of a reflecting surface to reflect a specific radio wave depends on which of the following factors?
1. Striking angle 2. Wavelength of the wave 3. Size of the reflecting area 4. All of the above
THIS SPACE LEFT BLANK INTENTIONALLY.
IN ANSWERING QUESTION 2-15, REFER TO FIGURE 2-A.
2-15. If the two reflected radio waves shown in the figure are received at the same instant at the receiving site, what will be the effect, if any, on signal quality?
1. A stronger signal will be produced 2. A weak or fading signal will be
produced 3. The signal will be completely canceled
out 4. None
2-16. The bending of a radio wave because of a change in its velocity through a medium is known as
1. refraction 2. reflection 3. deflection 4. diffraction
2-17. Radio communications can be diffracted to exceptionally long distances through the use of (a) what frequency band at (b) what relative power level?
1. (a) Very low frequency (b) Low power
2. (a) Very high frequency (b) Low power
3. (a) Very low frequency (b) High power
4. (a) Very high frequency (b) High power
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2-18. Electrically charged particles that affect the propagation of radio waves are found in what atmospheric layer?
1. Troposphere 2. Ionosphere 3. Chronosphere 4. Stratosphere
2-19. Most weather phenomena take place in which of the following region of the atmosphere?
1. Troposphere 2. Ionosphere 3. Chronosphere 4. Stratosphere
2-20. Radio wave propagation has the least effect because of its constancy on which of the following atmospheric layers?
1. Troposphere 2. Ionosphere 3. Chronosphere 4. Stratosphere
2-21. Long range, surface-wave communications are best achieved when the signal is transmitted over seawater with (a) what polarization at (b) what relative frequency?
1. (a) Vertical (b) Low 2. (a) Vertical (b) High 3. (a) Horizontal (b) High 4. (a) Horizontal (b) Low
2-22. The Navy’s long-range vlf broadcasts are possible because of the advantages of which of the following types of propagation?
1. Diffraction 2. Ionospheric refraction 3. Repeated reflection and refraction 4. Both 2 and 3 above
2-23. A space wave (a) is primarily a result of refraction in what atmospheric layer and (b) extends approximately what distance beyond the horizon?
1. (a) Ionosphere (b) One-tenth farther
2. (a) Ionosphere (b) One-third farther
3. (a) Troposphere (b) One-third farther
4. (a) Troposphere (b) One-tenth farther
2-24. The signal of a space wave is sometimes significantly reduced at the receiving site because of which of the following interactions?
1. Space-wave refraction 2. Space-wave reflections 3. Ground-wave diffraction 4. Ground-wave reflections
2-25. For long-range communications in the hf band, which of the following types of waves is most satisfactory?
1. Sky wave 2. Space wave 3. Surface wave 4. Reflected ground wave
2-26. Ionization in the atmosphere is produced chiefly by which of the following types of radiation?
1. Alpha radiation 2. Cosmic radiation 3. Infrared radiation 4. Ultraviolet radiation
2-27. Ultraviolet waves of higher frequencies produce ionized layers at what relative altitude(s)?
1. Lower 2. Higher 3. Both 1 and 2 above
11
2-28. The density of ionized layers is normally greatest during which of the following periods?
1. At night 2. Before sunrise 3. Between early morning and late
afternoon 4. Between afternoon and sunset
2-29. Compared to the other ionospheric layers at higher altitudes, the ionization density of the D layer is
1. about the same 2. relatively low 3. relatively high
2-30. What two layers in the ionosphere recombine and largely disappear at night?
1. D and F 2. D and E 3. E and F2 4. F1 and F2
2-31. For hf-radio communications covering long distances, what is the most important layer of the ionosphere?
1. C 2. D 3. E 4. F
2-32. Refraction of a sky wave in the ionosphere is influenced by which of the following factors?
1. Ionospheric density 2. Frequency of the wave 3. Angle of incidence of the wave 4. All of the above
2-33. A 10-MHz wave entering the ionosphere at an angle greater than its critical angle will pass through the ionosphere and be lost in space unless which of the following actions is taken?
1. The ground wave is canceled 2. The frequency of the wave is increased 3. The frequency of the wave is decreased 4. The ground wave is reinforced
2-34. The distance between the transmitter and the nearest point at which refracted waves return to earth is referred to as the
1. skip distance 2. return distance 3. reception distance 4. ground-wave distance
2-35. When ground-wave coverage is LESS than the distance between the transmitter and the nearest point at which the refracted waves return to earth, which of the following reception possibilities should you expect?
1. No sky-wave 2. Weak ground wave 3. A zone of silence 4. Strong ground wave
2-36. The greatest amount of absorption takes place in the ionosphere under which of the following conditions?
1. When sky wave intensity is the greatest 2. When collision of particles is least 3. When the density of the ionized layer
is the greatest 4. When precipitation is greatest
2-37. Which of the following layers provide the greatest amount of absorption to the ionospheric wave?
1. D and E 2. D and F1 3. E and F1 4. F1 and F2
12
2-38. If the signal strength of an incoming signal is reduced for a prolonged period, what type of fading is most likely involved?
1. Selective 2. Multipath 3. Absorption 4. Polarization
2-39. Radio waves that arrive at a receiving site along different paths can cause signal fading if these waves have different
1. velocities 2. amplitudes 3. phase relationships 4. modulation percentages
2-40. The technique of reducing multipath fading by using several receiving antennas at different locations is known as what type of diversity?
1. Space 2. Receiver 3. Frequency 4. Modulation
2-41. The amount of rf energy lost because of ground reflections depends on which of the following factors?
1. Angle of incidence 2. Ground irregularities 3. Frequency of the wave 4. Each of the above
2-42. Receiving sites located near industrial areas can expect to have exceptionally large losses in signal quality as a result of which of the following propagation situations?
1. Absorption 2. Multihop refraction 3. Natural interference 4. Man-made interference
2-43. Which of the following ionospheric variation causes densities to vary with the axial rotation of the sun?
1. Daily variation 2. Seasonal variation 3. 27-day sunspot cycle 4. 11-year sunspot cycle
2-44. Which of the following ionospheric variation causes densities to vary with the position of the earth in its orbit around the sun?
1. Daily variation 2. Seasonal variation 3. 27-day sunspot cycle 4. 11-year sunspot cycle
2-45. Which of the following ionospheric variation causes densities to vary with the time of the day?
1. Daily variation 2. Seasonal variation 3. 27-day sunspot cycle 4. 11-year sunspot cycle
2-46. What relative range of operating frequencies is required during periods of maximum sunspot activity?
1. Lower 2. Medium 3. Higher
2-47. What factor significantly affects the frequency of occurrence of the sporadic-E layer?
1. Seasons 2. Latitude 3. Weather conditions 4. Ionospheric storms
13
2-48. What effect can the sporadic-E layer have on the propagation of sky waves?
1. Causes multipath interference 2. Permits long distance communications
at unusually high frequencies 3. Permits short-distance communications
in the normal skip zone 4. Each of the above
2-49. A sudden and intense burst of ultraviolet light is especially disruptive to communications in which of the following frequency bands?
1. Hf 2. Mf 3. Lf 4. Vlf
2-50. The density of what ionosphere layer increases because of a violent eruption on the surface of the sun?
1. D 2. E 3. F1 4. F2
2-51. Which irregular variation in ionospheric conditions can cause a waiting period of several days before communications return to normal?
1. Sporadic E 2. Ionospheric storms 3. Sudden ionospheric disturbance 4. Each of the above
2-52. For a radio wave entering the atmosphere of the earth at a given angle, the highest frequency at which refraction will occur is known by which of the following terms?
1. Usable frequency 2. Refraction frequency 3. Maximum usable frequency 4. Optimum working frequency
2-53. The most consistent communications can be expected at which of the following frequencies?
1. Critical frequency 2. Maximum usable frequency 3. Maximum working frequency 4. Optimum working frequency
2-54. If the optimum working frequency for a communications link is 4,250 kHz, what is the approximate maximum usable frequency?
1. 4,500 kHz 2. 5,000 kHz 3. 5,500 kHz 4. 6,000 kHz
2-55. In determining the success of radio transmission, which of the following factors is the LEAST predictable?
1. Antenna capabilities 2. Weather conditions along the path of
communication 3. Density of ionized layers 4. Presence of ionized layers
2-56. At frequencies above 100 MHz, the greatest attenuation of rf energy from raindrops is caused by which of the following factors?
1. Ducting 2. Heat loss 3. Scattering 4. Absorption
2-57. Under certain conditions, such as ducting, line-of-sight radio waves often propagate for distances far beyond their normal ranges because of which of the following factors?
1. Low cloud masses 2. Ionospheric storms 3. Temperature inversions 4. Frequency fluctuations
14
2-58. When ducting is present in the atmosphere, multihop refraction of line-of-sight transmission can occur because of which of the following factors?
1. Operating frequency of the transmitter 2. Height of the transmitting antenna 3. Angle of incidence of the radio wave 4. Each of the above
2-59. A propagation technique used to extend uhf transmission range beyond the horizon uses which of the following propagation characteristics?
1. Ground reflection 2. Ionospheric scatter 3. Tropospheric scatter 4. Atmospheric refraction
2-60. Communications by tropospheric scatter can be affected by which of the following conditions?
1. Sunspot activity 2. Atmospheric conditions 3. Ionospheric disturbances 4. All of the above
2-61. What effect, if any, does the radiation angle of a transmitting antenna have on the reception of communications by tropospheric scatter?
1. The lower the angle, the weaker the signal
2. The lower the angle, the stronger the signal
3. The lower the angle, the more susceptible the signal is to distortion
4. None
2-62. Which of the following descriptions of tropospheric scatter signal reception is NOT true?
1. Receiver signal strength decreases as the turbulence height is increased
2. The level of reception depends on the number of turbulences causing scatter
3. The energy received is the portion of the wave reradiated by the turbulence
4. Increased communications distance enables more turbulence to act on the signal, thereby raising the received signal level
2-63. The tropospheric scatter signal is often characterized by very rapid fading caused by which of the following factors?
1. Extreme path lengths 2. Multipath propagation 3. Turbulence in the atmosphere 4. Angle of the transmitted beam
2-64. For which of the following communications situations would turbulence in the troposphere scatter transmission?
1. 10 MHz, range 200 miles 2. 30 MHz, range 800 miles 3. 50 MHz, range 600 miles 4. 100 MHz, range 400 miles
15
Textbook assignment: Chapter 3, “Principles of Transmission Lines,” pages 3-1 through 3-58. ___________________________________________________________________________________
3-1. A transmission line is designed to perform
which of the following functions?
1. Disperse energy in all directions 2. Detune a transmitter to match the load 3. Guide electrical energy from point to
point 4. Replace the antenna in a
3-2. All transmission lines must have two ends, the input end and the output end. What other name is given to the input end?
1. Sending end 2. Generator end 3. Transmitter end 4. Each of the above
3-3. A measurement of the voltage to current ratio (Ein/I in) at the input end of a transmission line is called the
1. input-gain rate 2. input impedance 3. output impedance 4. voltage-gain ratio
3-4. Which of the following lines is NOT a transmission medium?
1. Load line 2. Coaxial line 3. Two-wire line 4. Twisted-pair line
3-5. Electrical power lines are most often made of which of the following types of transmission lines?
1. Twin-lead line 2. Shielded-pair line 3. Two-wire open line 4. Two-wire ribbon line
3-6. Uniform capacitance throughout the length of the line is an advantage of which of the following transmission lines?
1. Coaxial line 2. Twisted pair 3. Shielded pair 4. Two-wire open line
3-7. What is the primary advantage of a rigid coaxial line?
1. Low radiation losses 2. Inexpensive construction 3. Low high-frequency losses 4. Each of the above
3-8. Which of the following wave-guides is seldom used because of its large energy loss characteristics?
1. Metallic 2. Dielectric 3. Elliptical 4. Cylindrical
3-9. To some degree, transmission lines always exhibit which of the following types of losses?
1. I2R 2. Inductor 3. Dielectric 4. Each of the above
3-10. Skin effect is classified as which of the following types of loss?
1. Copper 2. Voltage 3. Induction 4. Dielectric
16
3-11. What transmission-line loss is caused by magnetic lines of force not returning to the conductor?
1. Copper 2. Radiation 3. Induction 4. Dielectric
3-12. What is the electrical wave-length of 1 cycle if the frequency is 60 hertz?
1. 125,000 meters 2. 1,250,000 meters 3. 5,000,000 meters 4. 20,000,000 meters
3-13. A transmission line 10 meters in length is considered to be electrically long at which of the following frequencies?
1. 60 kilohertz 2. 600 kilohertz 3. 6 megahertz 4. 60 megahertz
3-14. The conductance value of a transmission line represents which of the following values?
1. Expected value of current flow through
the insulation 2. Expected value of voltage supplied by
the transmitter 3. Value of the lump and distributed
4. Value of the lump and distributed constants of the line divided by impedance
3-15. Electrical constants in a transmission line
are distributed in which of the following ways?
1. Into a single device 2. Along the length of the line 3. According to the thickness of the line 4. According to the cross-sectional area
3-16. Leakage current in a two-wire transmission line is the current that flows through what component?
1. The resistor 2. The inductor 3. The insulator 4. The conductor
3-17. Conductance is the reciprocal of what electrical property?
1. Inductance 2. Resistance 3. Capacitance 4. Reciprocity
3-18. A transmission line that has current flowing through it has which, if any, of the following fields about it?
1. Electric field only 2. Magnetic field only 3. Both electric and magnetic fields 4. None of the above
3-19. Maximum transfer of energy from the source to the transmission line takes place when what impedance relationship exists between the source and the transmission line?
1. When the load impedance equals
source impedance 2. When the load impedance is twice the
source impedance 3. When the load impedance is half the
source impedance 4. When the load impedance is one-fourth
3-20. The characteristic impedance (Z0) of a transmission line is calculated by using which of the following ratios?
1. Rs to Rload of the line 2. Imax to Imin at every point along the line 3. E to I at every point along the line 4. Ein to Eo of the line
17
3-21. For a given voltage, what determines the amount of current that will flow in a transmission line?
1. Conductance 2. Spacing of the wires 3. Diameter of the wires 4. Characteristic impedance
3-22. When the impedance of a transmission line is measured, which of the following values frequently is NOT considered?
1. Inductance 2. Resistance 3. Conductance 4. Capacitance
3-23. The characteristic impedance of a long transmission line may be determined by using which of the following methods?
1. Trial and error 2. Calculating the impedance of the entire
line 3. Calculating the impedances at each end
of the line 4. Adding the impedances of successive
3-24. When should lumped values for transmission-line constants be used to calculate characteristic impedance?
1. When the line is short compared to one
wavelength 2. When the line is long compared to one
wavelength 3. When the line is infinitely long
3-25. In actual practice, the characteristic impedance of a transmission line is usually within which of the following resistance ranges?
1. 0 to 0.9 ohm 2. 1 to 49 ohms 3. 50 to 600 ohms 4. 601 to 1,000 ohms
3-26. The input impedance of a transmission line is affected by which of the following properties?
1. Radiation loss 2. Series inductance 3. Parallel capacitance 4. Each of the above
3-27. When a dc voltage is applied to a transmission line and the load absorbs all the energy, what is the resulting relationship between current and voltage?
1. They are in phase with each other 2. They are equal to Z0 of the line 3. They are out of phase with each other 4. They are evenly distributed along the
3-28. The initial waves that travel from the source to the load of a transmission line are referred to as what type of waves?
1. Incident 2. Refracted 3. Reflected 4. Diffracted
3-29. Waves that travel from the output end to the input end of a transmission line are referred to as what type of waves?
1. Incident 2. Refracted 3. Reflected 4. Diffracted
18
Figure 3-A.—Equivalent infinite transmission line.
IN ANSWERING QUESTION 3-30, REFER TO FIGURE 3-A. 3-30. When a dc voltage is applied to the
equivalent infinite line in the figure, which of the following conditions occurs along the length of the line?
1. Standing waves of voltage form 2. Standing waves of current form 3. Current flows indefinitely 4. Voltage appears for a short time
Figure 3-B.—Equivalent transmission line.
IN ANSWERING QUESTION 3-31, REFER TO FIGURE 3-B. 3-31. Compared to a dc input, what relative
amount of time is required for an ac input voltage to travel the length of the line shown in the circuit?
1. Less 2. Same 3. More
3-32. The instantaneous voltage on an infinite transmission line can be plotted against time by using which of the following instruments?
1. A wavemeter 2. A multimeter 3. An oscilloscope 4. A spectrum analyzer
3-33. On an infinite transmission line with an ac
voltage applied, which of the following is an accurate description of the effective voltage distribution along the line?
1. Voltage is 0 at all points 2. Voltage is constant at all points 3. Voltage varies at a sine-wave rate 4. Voltage varies at double the sine-wave
3-34. The velocity of propagation on a transmission line is controlled by which of the following line characteristics?
1. Conductance 2. Inductance only 3. Capacitance only 4. Capacitance and inductance
3-35. The total charge on a transmission line is equal to the current multiplied by which of the following factors?
1. Time 2. Power 3. Voltage 4. Resistance
19
3-36. With only capacitance and inductance of the line given, the time (T) required for a voltage change to travel down a transmission line can be found by what formula? The characteristic impedance for an infinite transmission line can be figured using which of the following ratios?
1.
3.
2.
4.
3-37. The characteristic impedance for an infinite transmission line can be figured using which of the following ratios?
1. Input current to velocity 2. Input voltage to input current 3. Input voltage to line resistance 4. Input current to line resistance
3-38. The characteristic impedance of a
transmission line can be figured by using which of the following formulas?
1.
3.
2. 4.
Figure 3-C.—Equivalent transmission line.
IN ANSWERING QUESTIONS 3-39 AND 3-40, REFER TO FIGURE 3-C. ASSUME THAT THE LINE IS 1,200 FEET LONG. A 150-FOOT SECTION IS MEASURED TO DETERMINE L AND C. THE 150-FOOT SECTION HAS AN INDUCTANCE OF 0.36 MILLIHENRIES AND A CAPACITANCE OF 1,000 PICOFARADS. 3-39. What is the characteristic impedance of
the line?
1. 400 ohms 2. 600 ohms 3. 800 ohms 4. 900 ohms
3-40. What is the velocity of the wave on the 150-foot section?
1. 210,000,000 fps 2. 225,000,000 fps 3. 250,000,000 fps 4. 275,000,000 fps
3-41. If a transmission line is open-ended, which of the following conditions describes its terminating impedance?
1. Finite 2. Infinitely large 3. Equal to load impedance 4. Equal to source impedance
20
3-42. When a transmission line is not terminated in its characteristic impedance (Z0), what happens to the incident energy that is NOT transferred to the load?
1. It is returned along the transmission
line 2. It is radiated into space 3. It is absorbed by the line 4. It is converted to heat energy
Figure 3-D.—Open-ended transmission line.
IN ANSWERING QUESTIONS 3-43 AND 3-44, REFER TO FIGURE 3-D. 3-43. When the dc voltage reaches the open end
of the transmission line in the figure and is reflected, it has which, if any, of the following changes?
1. Increased amplitude 2. Decreased amplitude 3. The opposite polarity 4. None of the above
3-44. When the dc current reaches the open end
of the transmission line and is reflected, it has which, if any, of the following changes?
1. Increased amplitude 2. Decreased amplitude 3. The opposite polarity 4. None of the above
Figure 3-E.—Short-circuited transmission line.
IN ANSWERING QUESTIONS 3-45 AND 3-46, REFER TO FIGURE 3-E. 3-45. When the dc voltage reaches the shorted
end of the transmission line, it is reflected. It has which, if any, of the following changes?
1. Increased amplitude 2. Decreased amplitude 3. The opposite polarity 4. None
3-46. When the dc current reaches the shorted end of the transmission line, it is reflected. It has which, if any, of the following changes?
1. Decrease amplitude 2. Increase amplitude 3. Increased polarity 4. None of the above
21
3-47. In an open-ended transmission line with an ac signal applied, what is the phase relationship between the incident and reflected voltage waves?
1. In phase 2. 45 degrees out of phase 3. 90 degrees out of phase 4. 180 degrees out of phase
3-48. The resultant of the incident and reflected voltage waves is called the standing wave. Its value is figured by using which of the following procedures?
1. Adding the effective values of the two
waveforms 2. Algebraically adding the instantaneous
values of the two waveforms 3. Algebraically subtracting the
4. Taking the square root of the product of the incident and reflected voltages
3-49. On an open-ended transmission line that is
carrying an ac signal, what is the total number of moving voltage waves?
1. One 2. Two 3. Three 4. Four
3-50. At the end of an open-ended transmission line, which, if any, of the following voltage waves is at its maximum value?
1. Incident 2. Reflected 3. Resultant 4. None
3-51. On a transmission line that is carrying an ac signal, what is the relative value of the resultant voltage wave 1/4 wavelength from the open end?
1. Maximum positive 2. Maximum negative 3. Zero
3-52. In an open-ended transmission line, the resultant ac current waveform is always zero at what point(s)?
1. At the open end only 2. 1/2 wavelength from the open-end only 3. At the open end and 1/2 wavelength
3-53. The resultant waveform obtained by adding the incident wave to the reflected wave is referred to as a/an
1. standing wave 2. negative wave 3. algebraic wave 4. concentrated wave
3-54. On an open-ended transmission line, what is the phase relationship between the standing waves of voltage and current?
1. In phase 2. 45 degrees out of phase 3. 90 degrees out of phase 4. 180 degrees out of phase
3-55. Which of the following conditions exist at the end of a shorted transmission line?
1. Maximum voltage and minimum
current 2. Maximum voltage and maximum
current 3. Minimum voltage and maximum
current 4. Minimum voltage and minimum
3-56. Transmission line is considered to be nonresonant (flat) when it is terminated in which of the following ways?
1. In an impedance equal to Z0 2. In an impedance that is infinite 3. In an inductive reactance greater than
Z0 4. In a capacitive reactance greater than
22
3-57. Of the following terms, which one is used for the nonresonant transmission line?
1. A tuned line 2. A shorted line 3. An untuned line 4. A terminated line
3-58. A transmission line that is resonant is sometimes referred to as which of the following types of lines?
1. Tuned 2. Matched 3. Untuned 4. Unmatched
3-59. A short-circuited section of transmission line that is an odd number of quarter- wavelengths long shows the same characteristics as which of the following devices?
1. A series-resonant circuit 2. A parallel-resonant circuit 3. An inductive reactance equal to Z0 4. A capacitive reactance equal to Z0
3-60. Which of the following circuits appears as a very high resistance at resonance?
1. Nonresonant 2. Series-resonant 3. Parallel-resonant 4. Each of the above
3-61. When a series-resonant circuit is resonant at a frequency above the generator frequency, it acts as what type of circuit?
1. Open 2. Resistive 3. Inductive 4. Capacitive
3-62. Which of the following sections of transmission line can be used as a parallel- resonant circuit?
1. A shorted 1/4-wavelength section 2. An open 1/4-wavelength section 3. A shorted 1/2-wavelength section 4. An open 3/4-wavelength section
3-63. A generator connected to an open-ended line greater than 1/4 wave-length but less than 1/2 wave-length senses which of the following circuit component characteristics?
1. Zero reactance 2. Low resistance 3. Inductive reactance 4. Capacitive reactance
3-64. Which of the following conditions of current (I) and impedance (Z) exist at even quarter-wave points on a shorted transmission line?
1. Low I, low Z 2. Low I, high Z 3. High I, high Z 4. High I, low Z
3-65. What is the maximum distance, in wavelengths (λ), between adjacent zero- current points on an open-circuited line?
1. 1 λ 2. 1/2 λ 3. 1/4 λ 4. 1/8 λ
3-66. When a line is terminated in a capacitance, the capacitor performs which, if any, of the following circuit actions?
1. It absorbs all the energy 2. It reflects all the energy 3. It reacts as if it were a short 4. None
23
3-67. When a transmission line is terminated in an inductive reactance, which, if any, of the following phase shifts takes place with respect to the current and voltage?
1. Only voltage is phase-shifted 2. Only current is phase-shifted 3. Both voltage and current are phase-
shifted 4. None
3-68. When a transmission line is terminated in a resistance greater than Z0, which of the following conditions exist?
1. The end of the line appears as an open
circuit 2. Standing waves appear on the line 3. Voltage is maximum and current is
minimum at the end of the line 4. Each of the above
3-69. On a transmission line, reflections begin at which of the following locations?
1. At the load 2. At the source 3. At the middle 4. At the half-wavelength point
3-70. The ratio of maximum voltage to minimum voltage on a transmission line is referred to as the
1. rswr 2. pswr 3. vswr 4. iswr
3-71. Which of the following ratios samples the magnetic field along a line?
1. Vswr 2. Pswr 3. Iswr 4. Rswr
24
Textbook assignment: Chapter 4, “Antennas,” pages 4-1 through 4-60. ___________________________________________________________________________________
4-1. Radio energy is transmitted through which of the following mediums?
1. Rock 2. Soil 3. Water 4. Space
4-2. Energy is transmitted from a transmitter into space using which of the following devices?
1. A receiver 2. A delay line 3. A receiving antenna 4. A transmitting antenna
4-3. Transmitted rf energy takes what form as it is sent into space?
1. A magnetic field only 2. An electric field only 3. An electromagnetic field 4. A static dielectric field
4-4. The dimensions of a transmitting antenna are determined by which of the following factors?
1. Transmitted power 2. Transmitted frequency 3. Distance to the receiver 4. Antenna height above the ground
4-5. A device used to radiate or receive electromagnetic wave energy is referred to as a/an
1. feeder 2. antenna 3. transmitter 4. coupling device
4-6. An antenna that can be mounted to radiate rf energy either vertically or horizontally is classified as which of the following types?
1. Hertz 2. Marconi 3. Quarter-wave 4. Both 2 and 3 above
4-7. A complete antenna system consists of which of the following components?
1. A feeder, a coupling device, and a
transmitter 2. A feeder line, a coupling device, and
an antenna 3. An antenna, a transmission line, and a
receiver 4. An impedance-matching device, a
4-8. What component in an antenna system transfers energy from the transmitter to the antenna?
1. A feeder 2. A delay line 3. A choke joint 4. A rotating joint
4-9. The type, size, and shape of an antenna are determined by which of the following factors?
1. Power output of the transmitter 2. Transmitter frequency 3. Direction to the receiver 4. Each of the above
25
4-10. Moving electric and magnetic fields in space have what (a) phase and (b) angular relationships?
1. (a) In phase
(b) Perpendicular 2. (a) In phase
(b) Displaced 45º 3. (a) Out of phase
(b) Displaced 45º 4. (a) Out of phase
4-11. What is the length of each half of the wire for a dipole antenna?
1. Wavelength 2. 3/4 wavelength 3. 1/2 wavelength 4. 1/4 wavelength
4-12. On a dipole antenna, the sinusoidal variation in charge magnitude lags the sinusoidal variation in current by what amount?
1. 1 cycle 2. 1/2 cycle 3. 1/4 cycle 4. 1/8 cycle
4-13. On a standing wave, the points of high current and voltage are identified by which of the following terms?
1. Peaks 2. Nodes 3. Poles 4. Loops
4-14. The presence of standing waves indicates which of the following conditions of an antenna?
1. Resonance 2. Saturation 3. Nonresonance 4. Minimum efficiency
4-15. The antenna property that allows the same antenna to both transmit and receive energy is
1. gain 2. resonance 3. reciprocity 4. directivity
4-16. There is a ratio between the amount of energy propagated in certain directions by a directional antenna compared to the energy that would be propagated in these directions if the antenna were not directional. This ratio is known as which of the following antenna characteristics?
1. Gain 2. Directivity 3. Reciprocity 4. Polarization
4-17. The polarization plane of the radiation field is determined by which of the following fields?
1. Electric field only 2. Magnetic field only 3. Electromagnetic field
4-18. For best reception of a signal from a horizontally polarized antenna, the receiving antenna should be mounted so that it has what relationship with the transmitting antenna?
1. 0 degrees 2. 45 degrees 3. 90 degrees 4. 135 degrees
4-19. An electric field that rotates as it travels through space exhibits what type of polarization?
1. Vertical 2. Spherical 3. Elliptical 4. Horizontal
26
4-20. For ground-wave transmissions, what type of polarization is required?
1. Vertical 2. Spherical 3. Elliptical 4. Horizontal
4-21. For high-frequency operation, which of the following antenna polarization patterns is preferred?
1. Vertically polarized 2. Spherically polarized 3. Elliptically polarized 4. Horizontally polarized
4-22. Omnidirectional transmission is obtained from which of the following antennas?
1. Elliptically polarized 2. Horizontal half-wave 3. Vertical half-wave 4. Each of the above
4-23. With an antenna height of 40 feet and a transmitter frequency of 90 megahertz, which of the following antenna radiation patterns is best for transmitting over bodies of water?
1. Vertically polarized 2. Spherically polarized 3. Elliptically polarized 4. Horizontally polarized
4-24. To select a desired signal and discriminate against interfering signals from strong vhf and uhf broadcast transmissions, which of the following actions should you take?
1. Increase receiver gain 2. Make the transmitting antenna bi-
directional 3. Use a vertically polarized receiving
antenna 4. Use narrowly directional arrays as
4-25. A vertically mounted transmission line is LEAST affected by which of the following antenna radiation patterns?
1. Vertically polarized 2. Spherically polarized 3. Horizontally polarized 4. Elliptically polarized
4-26. An antenna with which of the following radiation resistance values will exhibit reduced efficiency?
1. 39 ohms 2. 82 ohms 3. 107 ohms 4. 150 ohms
4-27. An isotropic radiator radiates energy in which of the following patterns?
1. Vertical 2. Bi-directional 3. Unidirectional 4. Omnidirectional
4-28. An ordinary flashlight is an example of what type of radiator? 1. Isotropic 2. Polarized 3. Anisotropic 4. Stroboscopic
THIS SPACE LEFT BLANK INTENTIONALLY.
27
Figure 4-A.—Rectangular-coordinate graph.
IN ANSWERING QUESTION 4-29, REFER TO FIGURE 4-A. 4-29. How many points on the graph can
represent the value of 7 radiation units at position 2 of the circle?
1. One 2. Two 3. Three 4. Four
Figure 4-B.—Polar-coordinate graph.
IN ANSWERING QUESTIONS 4-30 AND 4-31, REFER TO FIGURE 4-B.
4-30. Compared with the rectangular- coordinate graph, the polar-coordinate graph has the advantage of showing which of the following antenna characteristics?
1. Polarization 2. Radiation pattern 3. Phase relationship 4. Gain versus directivity
4-31. The area enclosed by the radiation pattern is the
1. lobe 2. null 3. axis 4. coordinate
4-32. Inserting an inductor or capacitor in series with an antenna is one method of electrically changing the electrical length of an antenna. What is this method called?
1. Loading 2. Inserting 3. Unloading 4. Decoupling
4-33. Many complex antennas are constructed
from what basic antenna?
1. The Marconi antenna 2. The full-wave antenna 3. The half-wave antenna 4. The quarter-wave antenna
4-34. On an energized half-wave antenna, which of the following electrical conditions exist?
1. Voltage is maximum at the ends 2. Voltage is minimum at the ends 3. Current is maximum at the ends 4. Impedance is minimum at the center
28
4-35. Which of the following radiation patterns is/are exhibited by a simple vertical doublet antenna?
1. Nondirectional in the horizontal plane 2. Directional in the vertical plane 3. Both 1 and 2 above 4. Spherical in all planes
4-36. A method of feeding energy to a half- wave antenna is to connect one end through a capacitor to the output stage. What is this method of feeding called?
1. End feed 2. Voltage feed 3. Both 1 and 2 above 4. Current feed
4-37. An antenna supplied by the center-feed method is fed at what point?
1. Low voltage and low current 2. Low voltage and high current 3. High voltage and low current 4. High voltage and high current
4-38. The basic Marconi antenna has which of
the following characteristics?
1. One-quarter wavelength and ungrounded
2. One-half wavelength and grounded at one end
3. One-half wavelength and insulated from ground
4. One-quarter wavelength and grounded at one end
4-39. The Marconi antenna behaves as a dipole
for which of the following reasons?
1. It is fed at one end 2. An image antenna is formed by
reflections from the ground 3. A quarter-wavelength of conductor is
4. The applied signal is rectified so that only half the signal will appear on the quarter-wave antenna
4-40. A series of conductors arranged in a radial pattern and buried in the ground beneath the antenna is referred to as a
1. ground spur 2. counterpoise 3. ground screen 4. ground reflector
4-41. A folded dipole can be used instead of a simple, center-fed dipole for which of the following purposes?
1. Matching voltage 2. Matching impedance 3. Increasing directivity 4. Decreasing directivity
4-42. An antenna arrangement that has elements aligned in a straight line is referred to as what type array?
1. Isotropic 2. Collinear 3. Line-of-sight 4. Unidirectional
4-43. To have current in two adjoining
collinear half-wave elements in proper phase, they must be connected by which of the following stubs?
1. A shorted half-wave stub 2. An open quarter-wave stub 3. A shorted eighth-wave stub 4. A shorted quarter-wave stub
4-44. To select a desired signal and discriminate against interfering signals, the receiving antenna should have which of the following characteristics?
1. Be omnidirectional 2. Be highly directional 3. Be vertically polarized 4. Be horizontally polarized
29
4-45. Adding more elements to a collinear antenna array produces which of the following effects?
1. Increased gain 2. Decreased gain 3. Decreased directivity 4. Mismatched impedances
4-46. What is the maximum number of elements ordinarily used in a collinear array?
1. One 2. Two 3. Three 4. Four
4-47. Constructing a collinear array with elements longer than 1/2 wavelength has which of the following effects on antenna characteristics?
1. Increased gain 2. Decreased gain 3. Increased frequency range 4. Decreased frequency range
4-48. In a two-element collinear array,
maximum gain is obtained when the center-to-center spacing between the ends of the elements is approximately what electrical distance?
1. Wavelength 2. 0.15 wavelength 3. 0.5 wavelength 4. 0.75 wavelength
4-49. Compared with collinear arrays, broadside arrays have which of the following advantages?
1. Sharper tuning 2. Broader bandwidth 3. Broader frequency response 4. Less coupling between dipole
4-50. Optimum gain is obtained from a broadside array when the spacing of its elements is which of the following distances?
1. One-half wavelength 2. One-quarter wavelength 3. Greater than one-half wavelength 4. Slightly less than one-quarter
4-51. An end-fire array physically resembles the collinear array except that it is more compact. What disadvantage does the endfire array possess?
1. It has lower gain 2. It has low radiation resistance 3. It has loose coupling 4. Each of the above
4-52. What is the range of electrical spacing between the elements of an end-fire array?
1. 3/4 to 1 wavelength 2. 1/2 to 3/4 wavelength 3. 1/4 to 1/2 wavelength 4. 1/8 to 1/4 wavelength
4-53. The end-fire array produces what type of lobes, if any, along the axis of the array?
1. Minor lobes 2. Major lobes 3. None
4-54. Assuming that the elements are correctly spaced, the directivity of an end-fire array may be increased by which of the following actions?
1. Increasing the frequency 2. Decreasing the frequency 3. Decreasing the number of elements 4. Increasing the number of elements
30
4-55. A unidirectional pattern can be obtained from an end-fire array by using what phase relationship between the energy fed to adjacent elements?
1. 0º 2. 45º 3. 90º 4. 180º
4-56. Energy is fed to a parasitic element using what method?
1. Direct coupling 2. Inductive coupling 3. Capacitive coupling 4. Transmission-line coupling
4-57. The directivity pattern resulting from the action of parasitic elements depends on which of the following element characteristics?
1. Length of the element 2. Diameter of the element 3. Spacing between parasitic and driven
elements 4. Each of the above
4-58. The advantages of unidirectivity and increased gain can best be obtained by using which of the following elements in a parasitic array?
1. Driven elements only 2. Reflector and director elements only 3. Reflector, director, and driven
elements 4. Driven and director elements only
4-59. The ratio of energy radiated by an array in the principal direction of radiation to the energy radiated in the opposite direction describes which of the following relationships?
1. Side-to-side ratio 2. Front-to-back ratio 3. Driven-to-parasitic ratio 4. Reflector-to-director ratio
4-60. The Yagi antenna is an example of what type of antenna array?
1. Driven 2. End-fire 3. Multielement parasitic 4. Single-element parasitic
4-61. The addition of parasitic elements to the Yagi antenna has which of the following effects on antenna characteristics?
1. Increased gain 2. Narrower beam width 3. Narrower frequency response 4. Each of the above
4-62. An antenna which is designed especially for vertically-polarized ground waves at low frequencies is the
1. Yagi antenna 2. Marconi antenna 3. Beverage antenna 4. V antenna
4-63. What is the phase relationship of the signals that feed the V antenna?
1. 0º 2. 45º 3. 90º 4. 180º
4-64. A rhombic antenna is essentially a combination of which of the following antennas?
1. Two stacked long-wire radiators 2. Two V antennas placed side by side 3. Two collinear arrays in parallel 4. Four parallel half-wave radiators
4-65. A rhombic antenna has which of the following advantages?
1. Simple construction 2. Wide frequency range 3. Noncritical adjustment 4. Each of the above
31
4-66. The principal disadvantage of the rhombic antenna is its
1. poor directivity 2. large antenna site 3. low antenna voltage 4. high-frequency inefficiency
4-67. The unidirectional radiation pattern of the rhombic antenna is caused by which of the following antenna characteristics?
1. Size 2. Shape 3. Termination resistance 4. Frequency of the input energy
4-68. Horizontal half-wave antennas mounted at right angles to each other in the same horizontal plane make up which of the following antennas?
1. Rhombic 2. Flat-top 3. Turnstile 4. Ground-plane
4-69. The most common means of obtaining a
low-radiation angle from a vertical quarter-wave antenna is by what procedure?
1. Decreasing power 2. Increasing frequency 3. Adding a ground plane 4. Rotating the antenna to a horizontal
4-70. A corner reflector antenna is used for which of the following purposes?
1. To decrease frequency range 2. To increase frequency range 3. To produce a unidirectional pattern 4. To produce an omnidirectional
4-71. If a corner-reflector antenna is horizontally polarized, its radiation pattern will take on what shape?
1. A narrow beam in the horizontal
plane 2. A narrow beam in the vertical plane 3. A beam similar to a half-wave dipole
in the horizontal plane 4. A beam similar to a half-wave dipole
4-72. When radio or radar antennas are energized by transmitters, you must not go aloft until which of the following requirements are met?
1. A safety harness has been issued to
you 2. All transmitters are secured and
tagged 3. A working aloft "chit" has been filled
out and signed by proper authority 4. Each of the above


class: center, middle, inverse, title-slide # SQL to R ## Extra credit presentation ### Asha Yadav ### University of Oregon ### March 4th, 2020 --- # Objective ### 1. Connect with a database using R ### 2. Run SQL (Structure Query Language) queries using RSQLite(package) and dplyr in R --- # Database type and R packages ## R Package (left) and Database type (right): .pull-left[ 1. RMySQL 1. RPostgreSQL 1. RSQLite 1. odbc 1. bigrquery ] .pull-right[ 1. MySQL and MariaDB 1. Postgres and Redshift 1. SQLite 1. Many commercial databases 1. GoogleBigQuery ] --- # File structure ### 1. Flat rectangular files ### 2. Longitudinal/multiwave study files (Hierarchical files) ### 3. *Relational Database (SQLite)* <img src="picture1.png" width="80%" /> --- # Connect ## Connect to database using 'RSQLite' and 'dbplyr' (R packages) ### 1. Focuses on RETRIEVING and ANALYZING dataset (SELECT SQL statement). ### 2. It doesn’t MODIFY the dataset. ### 3. It doesn’t UPDATE or DELETE entries in database. --- # Step 1 Packages required ```r library(dplyr) library(dbplyr) library(RSQLite) ``` Downloaded the database for demonstration purpose. ```r dir.create("data_raw", showWarnings = FALSE) download.file(url = "https://ndownloader.figshare.com/files/2292171", destfile = "data_raw/portal_mammals.sqlite", mode = "wb") ``` --- # Step 2 Connect command ```r mammals <- DBI::dbConnect(RSQLite::SQLite(),"data_raw/portal_mammals.sqlite") ``` ### 1. DBI allows R to send commands to database regardless of database mgmt system. ### 2. RSQLite package allows R to interface with SQLite database. ### 3. We are not loading data in R instead we are only connecting at this stage. --- # Step 3 To view tables from the database ```r src_dbi(mammals) ``` ``` ## src: sqlite 3.30.1 [D:\Winter 2020\EDLD 610 Data Science 2\Extracredit\sql_to_r\data_raw\portal_mammals.sqlite] ## tbls: plots, species, surveys ``` ## Argument 'src_dbi' views tables in the database. Here we got: ###- plots ###- species ###- surveys --- # Step 4 Querying database with SQL syntax ```r tbl(mammals, sql("SELECT year, species_id, plot_id FROM surveys")) ``` ``` ## # Source: SQL [?? x 3] ## # Database: sqlite 3.30.1 [D:\Winter 2020\EDLD 610 Data Science ## # 2\Extracredit\sql_to_r\data_raw\portal_mammals.sqlite] ## year species_id plot_id ## <int> <chr> <int> ## 1 1977 NL 2 ## 2 1977 NL 3 ## 3 1977 DM 2 ## 4 1977 DM 7 ## 5 1977 DM 3 ## 6 1977 PF 1 ## 7 1977 PE 2 ## 8 1977 DM 1 ## 9 1977 DM 1 ## 10 1977 PF 6 ## # ... with more rows ``` --- # Step 4 Continues... ### 1. To retrieve data from the tables in the database, you can connect using **tbl()** function from dplyr. ### 2. If you know SQL, you can use any SQL queries to work with the database. ### 3. But same operations can be done in dplyr instead of using SQL. --- # Step 5 Querying database with dplyr syntax ```r surveys <- tbl(mammals, "surveys") surveys%>% select(year, species_id, plot_id) ``` ``` ## # Source: lazy query [?? x 3] ## # Database: sqlite 3.30.1 [D:\Winter 2020\EDLD 610 Data Science ## # 2\Extracredit\sql_to_r\data_raw\portal_mammals.sqlite] ## year species_id plot_id ## <int> <chr> <int> ## 1 1977 NL 2 ## 2 1977 NL 3 ## 3 1977 DM 2 ## 4 1977 DM 7 ## 5 1977 DM 3 ## 6 1977 PF 1 ## 7 1977 PE 2 ## 8 1977 DM 1 ## 9 1977 DM 1 ## 10 1977 PF 6 ## # ... with more rows ``` ```r head(surveys) ``` ``` ## # Source: lazy query [?? x 9] ## # Database: sqlite 3.30.1 [D:\Winter 2020\EDLD 610 Data Science ## # 2\Extracredit\sql_to_r\data_raw\portal_mammals.sqlite] ## record_id month day year plot_id species_id sex hindfoot_length weight ## <int> <int> <int> <int> <int> <chr> <chr> <int> <int> ## 1 1 7 16 1977 2 NL M 32 NA ## 2 2 7 16 1977 3 NL M 33 NA ## 3 3 7 16 1977 2 DM F 37 NA ## 4 4 7 16 1977 7 DM M 36 NA ## 5 5 7 16 1977 3 DM M 35 NA ## 6 6 7 16 1977 1 PF M 14 NA ``` - Object 'surveys' behaves like a dataframe. - All the functions that we have used for dataframes can be applied here onwards. --- # SQL Translation - These dplyr commands are not executed by R. - It is sent to database and final result is retrieved. - It brings only first 10 results (called dplyr 'Laziness') ```r surveys%>% filter(weight < 5) %>% select(species_id, sex, weight) ``` ``` ## # Source: lazy query [?? x 3] ## # Database: sqlite 3.30.1 [D:\Winter 2020\EDLD 610 Data Science ## # 2\Extracredit\sql_to_r\data_raw\portal_mammals.sqlite] ## species_id sex weight ## <chr> <chr> <int> ## 1 PF M 4 ## 2 PF F 4 ## 3 PF <NA> 4 ## 4 PF F 4 ## 5 PF F 4 ## 6 RM M 4 ## 7 RM F 4 ## 8 RM M 4 ## 9 RM M 4 ## 10 RM M 4 ## # ... with more rows ``` --- # dplyr Laziness - dplyr retrieves usually the first 10 results from the table. - Commands like select or filter to retrieve data from database are not executed by R. It is sent to the database and only final result is retrived and displayed. - To retrieve all of the dplyr results from the database ```r data_subset <- surveys %>% filter(weight < 5) %>% select(species_id, sex, weight) %>% collect() ``` - Now you have complete results from your query and you can continue working in R --- # Last but not the least ## Complex database queries - You can use dplyr to connect with multiple tables. - Did you know you can create a SQLite databse using csv files in R Leaving that for you to explore. ### Resources https://datacarpentry.org/R-ecology-lesson/05-r-and-databases.html#introduction https://db.rstudio.com/getting-started/database-queries/ ---


Method to query for a specific DataGroup record using the global ID value
| Param Name | Data | Length | Required | Description |
|---|---|---|---|---|
| SchemaFlag | Text | 10 | true | flag value to return the tabular result data with or without the DataTable metadata |
| rec_gid | Text | 40 | true | the global ID value for the TestResult record |
| Return Name | Data | Description | ||
| TestReplica.GetByID.base_DEFAULT | DataTable | the TestResult record found matching the ID value |
Method to query for the 1000 latest TestResult records
| Param Name | Data | Length | Required | Description |
|---|---|---|---|---|
| SchemaFlag | Text | 10 | true | flag value to return the tabular result data with or without the DataTable metadata |
| Return Name | Data | Description | ||
| TestReplica.GetAll.base_DEFAULT | DataTable | the set of the latest 1000 TestResult records |
Method to insert a new TestResult record
| Param Name | Data | Length | Required | Description |
|---|---|---|---|---|
| row_gid | Text | 10 | true | the unique global ID of the test result record |
| TestRun | Text | 100 | true | the name of the test run (batch of test methods) |
| Eval | Text | 10 | true | the code of the evaluation of the test method results |
| EvalInfo | Text | 250 | true | the summary of the evaluation of the test method results |
| APIMethod | Text | 50 | true | the full name of the API method called |
| AuthCode | Text | 10 | true | the actual authcode returned for the test method call |
| AuthInfo | Text | 250 | true | the authinfo returned from the server |
| ExpAuthCode | Text | 10 | true | the authcode expected for the test |
| ClientMS | Numeric | true | the total end-to-end duration of the method call in MS | |
| NetworkMS | Numeric | true | the time during transport (both ways) in MS | |
| ServerMS | Numeric | true | the elapsed time running the method on the server in MS | |
| UserName | Text | 50 | true | the name of the user running the test harness |
| CompName | Text | 50 | true | the name of the computer running the test harness |
| TimeStamp | DateTime2 | true | the datetime the test was run on the client | |
| ReqSize | Text | 50 | true | the size of the API Request message in bytes |
| RespSize | Text | 50 | true | the size of the API Response message in bytes |
| SvcURL | Text | 50 | true | the URL of the web service tested |
| FileName | Text | 50 | true | the name of the test file |
| Return Name | Data | Description | ||
| TestReplica.New.base_DEFAULT | Text | if successful, the result code of the insert of the new TestResult record; otherwise, the error message |


Programming - Game Development - Video Production
Note: Some of the methods and classes were given to us as a starting point for the assignment.
However, the parts described should all have been coded by me.
I am 1 years old and am a Newcastle University graduate who completed the Computer Science/ Game Development BSc course. I am extremely hard working and have proved this in my achievements to date, including obtaining a 1st Class degree with an overall mark of 77.7%. Below are both my qualifications and my work experience.
Newcastle University : BSc Computer Science (Game Engineering) : 1st Class (Hons)
Accrington and Rossendale College : BTEC Computer Science/Game Development : D*D*D*
St Christopher's CofE High School : GCSEs : A*-C
Summer of 2019 and 2020 : Factory Worker : Agrial Fresh
Summer of 2018 : Factory Worker : Salads to Go
Part time 2016-2018 : Retail Worker : Home Bargains
Email me at<EMAIL_ADDRESS>or
use the form below


Firestorm is an ORM for firestore which can be used with Typescript.
Firestorm relies on using Typescript's experimental decorators for defining your models. Please ensure you have the following in your tsconfig.json
:
{
"compilerOptions": {
"target": "ES5", /* or greater */
"experimentalDecorators": true,
"emitDecoratorMetadata": true,
}
}
$ npm install firebase-firestorm
In this section, we will walk you through an example of how a basic blogging database might look using posts, comments and authors.
Call firestorm.initialize(firestore, options?)
as soon as you intialize your firestore app. See intialization options for more information about intiailizing firestorm.
import * as firestorm from 'firebase-firestorm';
...
const firestore = firebase.initializeApp(...);
firestorm.initialize(firestore, /* options */);
...
Here we have a class representing a posts
collection. Entity classes are typically non-pluralized as they represent a single document from that collection. To define a root collection you must:
Entity
class.@rootCollection(opts: ICollectionConfig)
.@field(opts: IFieldConfig)
.import { Entity, rootCollection, field } from 'firebase-firestorm';
@rootCollection({
name: 'posts',
})
export default class Post extends Entity {
@field({ name: 'title' })
title!: string;
@field({ name: 'content' })
content!: string;
}
Each of your models, whether they represent a root collection or subcollection must extend from the
Entity
class provided.
Now we want documents in the posts
collection to have a subcollection of comments
. First, we need to create as class for the comments. Notice how we do not annotate the class with @rootCollection
.
import { Entity, rootCollection, field } from 'firebase-firestorm';
export default class Comment extends Entity {
@field({ name: 'content' })
content!: string;
@field({ name: 'by' })
by!: string;
}
Back in the Post
class, we can add Comment
as a subcollection using the @subCollection(opts: ISubcollectionConfig)
decorator.
import { Entity, ICollection, rootCollection, field } from 'firebase-firestorm';
import Comment from './Comment';
@rootCollection({
name: 'posts',
})
export default class Post extends Entity {
...
@subCollection({
name: 'comments',
entity: Comment, // we must define the entity class due to limitations in Typescript's reflection capabilities. Progress should be made on this issue in future releases.
})
comments!: ICollection<Comment>;
...
}
Finally we want documents in the posts
collection to reference an author in an authors
collection (another root collection). First, we define the Author
entity:
import { Entity, rootCollection, field } from 'firebase-firestorm';
@rootCollection({
name: 'authors',
})
export default class Author extends Entity {
@field({ name: 'name' })
name!: string;
}
Then we can add an Author
reference to the Post
entity using the @documentRef(opts: IDocumentRefConfig)
decorator:
import { Entity, ICollection, IDocumentRef, rootCollection, field } from 'firebase-firestorm';
import Author from './Author';
@rootCollection({
name: 'posts',
})
export default class Post extends Entity {
...
@documentRef({
name: 'author',
entity: Author, // we must define the entity class due to limitations in Typescript's reflection capabilities. Progress should be made on this issue in future releases.
})
author!: IDocumentRef<Author>;
...
}
Now we've built our model, we're ready to start querying. Calling Collection(entity : IEntity)
will return a list of methods use can use to manipulate the data.
...
const post = Collection(Post).get('post-1').then((post : Post) => {
console.log(post);
});
...
In our example Comment
is a subcollection of Post
. You can get subcollections from a retrieved document, or a document reference.
// Comment subcollection from document.
const post = Collection(Post).get('post-1').then((post : Post) => {
const commentCollection = post.collection(Post);
});
// Comment subcollection from document ref.
const postRef = Collection(Post).doc('post-1');
const commentCollection = postRef.collection(Post);
You can use the find(query : ICollectionQuery)
method to query data. A full list of options are available in the docs, but they are essentially the same as what is available with firestore.
const posts = Collection(Post).find({
where: [
['title', '==', 'Example Title'],
...
],
});
...
const post = new Post();
post.id = 'post-1'; // id is optional, if it is not defined it will be generated by firestore.
post.title = 'Untitled';
let savedPost : Post;
Collection(Post).create(post).then((_savedPost : Post) => {
savedPost = _savedPost;
});
...
...
const post = new Post();
post.id = 'post-1'; // id is required.
post.title = 'Untitled';
let savedPost : Post;
Collection(Post).update(post).then((_savedPost : Post) => {
savedPost = _savedPost;
});
...
...
Collection(Post).remove('post-id').then(...);
...
An instance of entity maybe contain properties such as subcollections which you do not wish to include if, for example, you are building a REST API. Calling the toData()
method on an instance of an entity will produce a plain JSON object containing just primitive data, nested JSON objects, and document reference which have already been retrieved using the .get()
method. For example:
import { Collection } from 'firebase-firestorm';
import Author from './Author';
import Post from './Post';
Collection(Post).get('post-1').then((post: Post) => {
console.log(post.toData());
/*
Output:
{
id: ...,
title: ...,
content: ...
}
*/
post.author.get().then((author: Author) => {
console.log(post.toData());
/*
Output:
{
id: ...,
title: ...,
content: ...,
author: {
id: ...,
name: ...
}
}
*/
});
});
Firestore documents can contain arrays of strings, numbers, objects, etc. Defining arrays in Firestorm is as simple as assigning properties as array types in your Entity
files. For example:
class Example extends Entity {
@field({ name: 'example_property_1' })
property1!: string[];
@field({ name: 'example_property_2' })
property2!: IDocumentRef<AnotherEntity>[];
}
Firestore documents can contains nested objects (or maps). For a nested object, you need to create a new class to represent that object, and add a property with that class in your Entity
, wrapped
with the @map
decorator.
class Example extends Entity {
@map({ name: 'nested_object' })
nestedObject!: Nested;
}
class Nested {
@field({ name: 'nested_property' })
nestedProperty!: string;
}
And then to use this entity:
...
const nested = new Nested();
nested.nestedProperty = 'test';
const example = new Example();
example.nestedObject = nested;
...
Geopoints store locational data and can be used a field. We have a wrapper class for firestore's GeoPoint which basically serves the same functionality.
class Example extends Entity {
@geopoint({
name: 'geopoint_property',
})
geopoint!: IGeoPoint;
}
And then to assign a GeoPoint:
...
const example = new Example();
example.geopoint = new Geopoint(latitude, longitude);
...
You can represent date & time data in your Entity
files. Like geopoints, our timestamp representation is essentially a wrapper of firestore's. You can set the options for the field to updateOnWrite
which uses the server timestamp when creating or updating documents, or updateOnCreate
or updateOnUpdate
.
class Example extends Entity {
@timestamp({
name: 'timestamp_property',
updateOnWrite: true,
})
timestamp!: ITimestamp;
}
firestorm.intialize({ ...opts : IFireormConfig })
can be called with the following options:
| Option | Description | Type |
|---|---|---|
fieldConversion |
Providing this option will convert Entity propertity names into firestore collection names so you don't need to provide the name option in @field() decorators. To view available values please check out the docs. |
enum FieldConversionType |
I
infront of the type, e.g. IDocumentRef
, ITimestamp
, IGeoPoint
. If you would like to help resolve these issues, feel free to make a a pull request.
$ cd firebase-firestorm
$ npm install
The testing script looks for *.spec.ts
files in the src
and test
directory.
$ npm test
Please report any bugs you have found submitting an issue to our Github repository, after ensuring the issue doesn't already exist. Alternatively, you can make a pull request with a fix.
If you would like to help add or a feature or fix a bug, you can do so by making a pull request. The project uses Conventional Commits, so please make sure you follow the spec when making PRs. You must also include relevant tests.
Generated using TypeDoc


University of Calgary is a vibrant community, with individuals hailing from many different backgrounds. All have diverse perspectives on life, love, learning, and everything in between.
Our objective is to share the stories and photos of students, faculty, alumni, and staff from UCalgary and create a greater sense of community.
Our Team
“Employers are no longer looking for a 4.0 student. They want people who are unafraid to do interesting, unconventional things.
You gain such a wealth of knowledge by going overseas.  During my undergrad I left for a semester to travel to Europe, and when I returned I knew what I wanted to get out of school and it helped me realize where I wanted to go. I think too many people are focused on starting their career. They might not realize that this is the best time to get out there and embrace something new, and maybe discover what you want to be in the future.
Now I work as an Instructor with the Haskayne School of Business and it has been amazing to give back to the program that has taught me so much.


The verb lab
in locale j
runs the lab system. It is invoked by selecting the lab menu items in the Studio menu; and by pressing the lab advance shortcut when a lab has been loaded.
lab
can also be called under program control as described below, and this can be helpful when creating and testing a lab. If you are using lab
in this way, you may want to define lab_z_=. lab_j_
to remove the need for the locale reference.
The form is:
lab '' | Lab dialog for files in system\extras\labs directory. Invoked by menu item Studio|Labs... |
lab 0 [,num] | Show next Lab Section (or section num). Invoked by menu item Studio|Advance, or by the corresponding shortcut key. |
lab 1 | Show jump dialog Invoked by menu item Studio|Jump... |
lab 2 | Run Lab Author Invoked by menu item Studio|Author... |
lab 'directory' | Show lab dialog for files with extension .ijt in given directory. |
lab 'filename'[;num] |
Invoke lab on given file (at chapter |
Note that you can run any file as a lab file, e.g.
lab 'system\extras\labs\labintro.txt'


Following a list of StaffRender features grouped by fuctional scope is exposed. They are the visual confirmation of the module unitary tests.
A showcase with a complete catalog of samples of the different graphic elements.
Related to the note split capability regarding to rhythm context.


Four card feature section
Single price grid component
FAQ accordion card
Order summary component
Huddle landing page
Article preview component
3-column preview card component
Base Apparel coming soon page
Ping single column coming soon page
Testimonials grid section
Tip calculator app
Intro component with sign-up form
Sunnyside agency landing page
Pricing component with toggle
Coding bootcamp testimonials slider
Interactive pricing component
Social media dashboard with theme switcher
Time tracking dashboard
Blogr landing page


Each document has the following fields:
| Property Name | Type | Description |
|---|---|---|
| class | String | The simple name of the enclosing class |
| qualifiedClass | String | The qualified of the enclosing class |
| name | String | The simple name |
| annotations | Array | An array of annotations |
| modifiers | Array | An array of modifiers ("public", "static", etc.) |
| description | String | A description of the method |
| since | String | Which JDK this first appeared in (may not be present) |
| path | String | The path of the documentation, relative to http://docs.oracle.com/javase/[version]/docs/api/ |
| kind | String | Always "method" |
| params | Array |
An array of parameter descriptors with the following properties:
|
| returnType | String | The return type of the method |
| throws | Array | An array of Exception subclass names declared by the method (subclasses of java.lang.RuntimeException are typically not declared) |
| returns | String | The description of the return value of the method (may not be present) |
{ "com.solveforall.recognition.programming.java.JdkMethod" : [ { "name" : "skip", "class" : "FileInputStream", "qualifiedClass" : "java.io.FileInputStream", "qualifiedName" : "java.io.FileInputStream.skip", "params" : [ { "type" : "long", "name" : "n", "description" : "the number of bytes to be skipped." } ], "annotations" : [], "modifiers" : ["public"], "returnType" : "long", "throws" : ["IOException"], "description" : "Skips over and discards n bytes of data from the\n input stream...", "returns" : "the actual number of bytes skipped.", "path" : "java/io/FileInputStream.html#skip(long)", "kind" : "method" }, ... ] }


--- title: Agile Events Are Habits excerpt: Our habits either help or hinder our agility. And nowhere else is it more visible than when people meet. date: '2023-08-28 15:08:07 +0100' categories: - Agile - General - Mindfulness - Motivation - Teams - Well-being image: path: /assets/images/social/agile_events_are_habits.jpg ---
Agile is fiercely people-first. And yet, agile frameworks come with prescribed events, artifacts, accountabilities, commitments and whatnot. Earlier, I’ve written about the oxymoron of agile habits: responding to change vs. running on autopilot. Today, I thought I’d focus on the first agile value: individuals and interactions over processes and tools. More specifically, I’ll talk about our agile meeting habits.
These meetings—or events as they’re called in Scrum—update or replace our existing meeting habits when done repeatedly. Sometimes these habits are even called “ceremonies”. I dislike that word because it implies putting process before people. Language is important. People-first means DEI, transparency, trust, commitment, flexibility and fun, among many other things. With people, one size does not fit all.
Daily Scrums, for example, consequently eliminate the need for other meetings
(The 2020 Scrum Guide). It sounds good in theory. However, if we merely bring our existing auto-pilot habits to these agile events, we’re setting ourselves up for failure—and in the worst case, perhaps end up having those other meetings, too!
This is even more important in a remote context, where most work happens both distributed and asynchronously. When we do meet synchronously, online or onsite, we should make it count. To make these events work for us, we need to be aware of both the existing organisational routines and people’s habits, and short-circuit the brain’s autopilot mode. Running these events on autopilot—as we do with any habit—kills agility.
Now, regarding agility: I believe that becoming more agile should be an intermediary goal. It’s a goal that co-exists with the product goal. Becoming more agile is a goal that we can control much more than our product goal. Becoming more agile increases the likelihood that we’ll reach our product goal and our desired outcome. Inspecting and adapting our agile events requires us to make our current habits transparent. It’s our habits that either help or hinder our agility.
Here are just some examples of our event habits:
Our understanding of our habits, and our ability to change them are much more important than our knowledge about the chosen agile framework.
We don’t want to stop thinking. So how can we stay alert, and inspect and adapt our agile teams’ events—or the wider organisation’s routines—if they don’t suit the purpose any longer? Our understanding of our habits, and our ability to change them are much more important than our knowledge about the chosen agile framework. The same is true for the wider organisation as well: what’s the point if only the agile teams change, if the organisational habits (routines) don’t change? I’m not talking about “us” and “them”; with “us”, I mean everyone in the whole organisation or ecosystem.
So that’s how I see individuals and interactions over processes and tools in practice and in reality. And nowhere else is it more visible than when people meet. To change is to change our habits by short-circuiting the brain’s autopilot mode. Easier said than done, but visualising our practices, asking questions, and in general, staying curious and proactive is a good start. By running a better routine you become the new you: a person who is not only more aware of the habit loop, but also someone who becomes iteratively more capable of delivering value in the team. Our ever-changing event habits are just one vehicle for that.


What Are Your Emails?
Halmon Lui<EMAIL_ADDRESS>Kevin Lin<EMAIL_ADDRESS>Aaron Cheng: aaroncheng@umass.edu


Two people injured in Campbell River incident, RCMP say
by Jeff BellCampbell River RCMP say two females were hurt after a Sunday incident in the Homalco First Nation community.
Police responded to a report of a fight there with unspecified weapons at 6:55 a.m. Both females, who are known to one another, were sent to Campbell River Hospital.
One was later sent to hospital in Victoria for further treatment of non-life-threatening injuries, while the other’s condition was not indicated.
Campbell River RCMP Const. Maury Tyre said it was an isolated occurrence and there are no safety concerns for the public. The Campbell River Major Crimes Unit is investigating.
Call Campbell River RCMP with any information about the case at<PHONE_NUMBER>.


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Product
FairyGUI Editor
Current version 3.10.7
Windows （32bit)Support Simplified Chinese, Traditional Chinese and English
Windows (64bit)Support Simplified Chinese, Traditional Chinese and English
OSXSupport Simplified Chinese, Traditional Chinese and English
FairyGUI Editor is green software, decompression can be used directly, no need to install. Recommended to extract to non-Chinese directory.
Old version download channel:
- Windows res.fairygui.com/FairyGUI-Editor_X_X_X.zip
- OSX res.fairygui.com/FairyGUI-Editor_Mac_X_X_X.zip
XXX will be replaced by the version number of the three numbers on it.
Unity SDK
In Unity：Open AssetStore, Search ‘FairyGUI’, and then download and import.
Source: https://github.com/fairygui/FairyGUI-unity
Cocos2dx SDK
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LayaAir SDK
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Egret SDK
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CocosCreator SDK
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Starling SDK
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PIXI SDK
Source: https://github.com/jcyuan/FairyGUI-PixiJS/releases
Haxe SDK
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Flash SDK
Source: https://github.com/fairygui/FairyGUI-as3
Cry Engine SDK
Source: https://github.com/fairygui/FairyGUI-cryengine
Havok Vision SDK
Source: https://github.com/fairygui/FairyGUI-vision
MonoGame SDK
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Joey B Cautions Men To Be Wary Of Women, Money
by Ghbase New WriterWomen and money are men’s weakness and there are a lot of nonfiction stories to substantiate this theory.
Rapper Joey B is much conscious of this too and has subsequently warned all men not be reduced to nothing when they have them in abundance.
The former Black Avenue Muzik signee said women and money can make or unmake a man hence men should be wary on how to deal with them.
He sounded this warning during an interview session with Andy Dosty on Hitz FM: “You are bound to fail if you cannot control women and money.
Money and Women can make and unmake you if you allow these two to control you”, he said.


Match Play. Double Match Point. How should Red play 51?
pips Red=110 White=100
(CorrectAnswer= 0/0, ErrorScore= 0)
Apologies for posting the wrong question yesterday!
For money 22/16 loses too many gammons to make the play viable but at DMP you need the play that wins that highest percentage of games.
22/16 wins nearly 3% more games than 12/7, 5/4, mainly because it preserves Red's five-point home board, so despite the play looking risky it is the correct play.
For money 22/16 loses too many gammons to make the play viable but at DMP you need the play that wins that highest percentage of games.
22/16 wins nearly 3% more games than 12/7, 5/4, mainly because it preserves Red's five-point home board, so despite the play looking risky it is the correct play.
1. Cubeful 2-ply 22/16 Eq.: -0.365 0.317 0.083 0.003 - 0.683 0.392 0.007 2. Cubeful 2-ply 12/7 5/4 Eq.: -0.438 (-0.073) 0.281 0.036 0.000 - 0.719 0.217 0.006 3. Cubeful 2-ply 12/7 2/1 Eq.: -0.444 (-0.079) 0.278 0.034 0.000 - 0.722 0.207 0.005 4. Cubeful 2-ply 12/7 3/2 Eq.: -0.444 (-0.079) 0.278 0.037 0.000 - 0.722 0.228 0.006 5. Cubeful 2-ply 12/7 4/3 Eq.: -0.446 (-0.081) 0.277 0.036 0.000 - 0.723 0.227 0.006