RHM ESAT 1 Part 1 1-100

1. The property of a radiator to emit strong radiation in one direction.

2. If the centre impedance of a folded dipole is approximately 300 ohms, and you are using RG8U (50 ohms) coaxial lines, what is the ratio required to have the line and the antenna matched?

3. What does vertical wave polarization mean?

4. An antenna has an impedance of 40 Ω. An unmodulated AM signal produces a current of 4.8 A. The modulation is 90 percent. Calculate the total power.

5. What electromagnetic wave polarization does a half-wavelength antenna have when it is perpendicular to the earth's surface?

6. It is an indirect method of generating FM using crystal oscillator for frequency stability with a phase-modulated buffer stage.

7. Approximately how long is the reflector element of a Yagi antenna for 28.1 MHz?

8. What are some advantages of a Yagi with wide element spacing?

9. What does "antenna front-to- back ratio" mean in reference to a Yagi antenna?

10. It is an FM detector using two slope detectors.

11. It is a variation of the Foster-Seeley discriminator which includes an amplitude limiter which improves the limiting action.

12. If the signal at the beginning of a cable (specified as 0.30 dB/km cable) has a power of 5mW, what is the power (in dBm) of the signal at 10 km?

13. It is an array in which one or more elements obtain power through mutual coupling with another element in the array.

14. It is the simplest array consisting of a number of dipoles of equal size, equally spaced along a straight line, with all dipoles fed in the same phase of the source.

15. It is a single antenna consisting of two elements. The fact that the second wire is folded makes the currents in the two conductors of the antenna flow in the same direction.

16. An array in which the direction of maximum radiation is perpendicular to the plane containing the elements.

17. An antenna array with all the elements in a straight line where the maximum radiation is perpendicular to the axis of the elements.

18. What is meant by receiver overload?

19. The spacing between the elements on a three- element Yagi antenna, representing the best overall choice, is _______ of a wavelength.

20. If you made a half-wavelength dipole antenna for 28.550 MHz, how long would it be?

21. What is the low angle radiation pattern of an ideal half-wavelength dipole HF antenna installed parallel to the earth?

22. If a neighbour reports television interference whenever you transmit, no matter what band you use, what is probably the cause of the interference?

23. When the signal from a transmitter overloads the audio stages of a broadcast receiver, the transmitted signal:

24. What connects your transceiver to your antenna?

25. A receiver has its local oscillator set to 550 MHz and its IF amplifier designed to work at 20 MHz. Find two signal frequencies that can be received.

26. The characteristic impedance of a 20 metre piece of transmission line is 52 ohms. If 10 metres were cut off, the impedance would be:

27. What commonly available antenna feed line can be buried directly in the ground for some distance without adverse effects?

28. Invented the telegraph

29. Invented the phonograph

30. Patented the photophone

31. It is a modulation technique wherein both the carrier and information are in analog forms.

32. Standard AM Intermediate Frequency

33. Is the curve produced by joining the tips of the individual RF cycles of a modulated wave.

34. It is a metallic conductor system used to transfer electrical energy from one point to another using electrical current flow.

35. Signals are emitted then radiated through air or a vacuum.

36. It is also known as single ended transmission lines or concentric transmission lines, which consists of a solid conductor surrounded by an insulator.

37. It is an electrical conductor or array of conductors that radiates signal energy or collects signal energy.

38. It is the primary beam of an antenna and the direction of maximum radiation.

39. Those lobes in front of the antenna or the major lobes that propagates and receive the most energy.

40. A half-wave antenna with a reflector consisting of two flat metal surfaces meeting at an angle behind the radiator.

41. An isotropic antenna is a:

42. VHF signals from a mobile station using a vertical whip antenna will normally be best received using a:

43. If an electromagnetic wave leaves an antenna vertically polarized, it will arrive at the receiving antenna, by ground wave:

44. It is the simplest and easiest to understand FM detector. It requires no tuned circuits.

45. It is the state when the PLL is in the process of acquiring frequency lock.

46. It is also known as tracking range, which is defined as the range of frequencies in the vicinity of the VCO's natural frequency over which the PLL can maintain lock with an input signal.

47. The total power content of an AM wave is 6000 W. For 100% modulation, what is the power transmitted by the carrier?

48. Consisting of several dipole elements of different lengths and relative spacing, fed from a two-wire line which is transposed between each adjacent pair dipoles.

49. It is a vertically polarized antenna consists of a wire loop above with an omnidirectional radiation pattern.

50. It is a type of antenna using tuned circuits of appropriate design that are strategically placed in a dipole.

51. Another name for antenna CENTER-FEED METHOD.

52. A common type of half-wave antenna made from a straight piece of wire cut in half. Each half operates at a quarter wavelength of the output.

53. What is cross-modulation interference?

54. The signal at the beginning of a cable with an attenuation of 0.4 dB/km is is 7mW, find the power 15km away.

55. What is the result of cross-modulation?

56. How can cross-modulation be reduced?

57. A transmission line differs from an ordinary circuit or network in communications or signaling devices in one very important way. That important aspect is:

58. Any length of transmission line may be made to appear as an infinitely long line by:

59. What factors determine the characteristic impedance of a coaxial antenna feed line?

60. Demonstrated wireless transmission

61. Invented frequency modulation radio

62. Invented the World Wide Web

63. The modulation takes place prior to the output element of the final stage of the transmitter.

64. A type of AM detector that consists of a diode in series with an RC low pass filter.

65. It is a type AM of detector using amplifying devices like transistors in place of a diode to provide rectification and amplification at the same time.

66. The tuned circuit the oscillator in a simple AM transmitter employs a 50 μH coil and a 1 nF capacitor. If the oscillator output is modulated by audio frequencies up to 10 kHz, calculate the range occupied by the side bands:

67. Also known as ribbon cable, and it is the same with open wire except that the spacers between the two conductors are replaced with a continuous solid dielectric.

68. Typical characteristic impedance for Twin Lead

69. Consists of two copper wires where each wire is separately encapsulated in PVC.

70. Those lobes in a direction exactly opposite of the front lobe.

71. It is the ratio of front lobe power to back lobe power.

72. It is the line bisecting the major lobe and it is pointing from the center of the antenna in the direction of maximum radiation.

73. An array in which all of the elements are driven.

74. How can the bandwidth of a parasitic beam antenna be increased?

75. If a slightly longer parasitic element is placed 0.1 wavelength away from an HF dipole antenna, what effect will this have on the antenna's radiation pattern?

76. Approximately how much gain does a half-wave dipole have over an isotropic radiator?

77. An array in which the direction of radiation is parallel to the axis of the array.

78. A coaxial line made with a flexible inner conductor insulated from the outer conductor by a solid, continuous insulating material.

79. How can you prevent key-clicks?

80. If your transmitter sends signals outside the band where it is transmitting, what is this called?

81. In Morse code transmission, local RF interference (key-clicks) is produced by:

82. What is parallel-conductor feed line?

83. What does the term "balun" mean?

84. What is an unbalanced line?

85. It uses a tapped coil as its feedback element

86. It is similar with Colpitts with an additional capacitor in series with the inductor in the feedback circuit.

87. It is a sinusoidal feedback oscillator that utilizes a lead-lag circuit

89. A type of AM detector that employs a tickler coil which generates energy from the plate circuit into the grid circuit of the triode.

90. To mix two frequencies together in a nonlinear device or to translate one frequency to another using nonlinear mixing.

91. It is a stable crystal oscillator whose frequency beats with the incoming signal to produce the correct intermediate frequency.

92. Current that flow in same direction

93. Also known as choke, sleeve, or bazooka balun.

94. Is an electromagnetic interference between two conductors that occurs when current flows through one conductor, it produces a magnetic field that can interfere with the adjacent conductor.

95. The field strength and power density is plotted with respect to the value at a reference point (variable power, fixed distance)

96. It is also known as the radiation field or the Fraunhoffer region. It is the distance far enough from an antenna that local inductive and capacitive effects are insignificant.

97. Refers to the input terminal of an antenna. A point in the antenna where the transmission line is connected or where the signal is being fed.

98. The ratio of the energy radiated in the principal direction to the energy radiated in the opposite direction.

99. What is meant by antenna bandwidth?

100. If a magnetic-base whip antenna is placed on the roof of a car, in what direction does it send out radio energy?