University of the Samar Island Archipelago (formerly Samar State University)

1)The theory of radio waves was originated by:

2. The first person who sent the first radio signal across the Atlantic ocean:

3. The transmission of radio waves was first done by:

4. When two or more signals share a common channel, it is called:

5. “Man-made” noise can come from:

6. Thermal noise is generated in:

7. Shot noise is generated in:

8. The power density of “flicker” noise is:

9. So called “1/f” noise is also called:

10. “Pink” noise has:

11. Noise figure is a measure of:

12. Resistor that generates the lowest thermal noise:

13. Resistor with typical voltage range of
14. Reference for noise temperature in

?C:

15. Standard test tone connected on audio equipment?

16. Reference standard test tone normally used is indicated in:

17. Power lost in device, due by the path of energy flow.

18. The noise generated with semiconductor devices.

19. Flicker noise in radio communications is also known as.

20. What determines the BW of a transmitted signal?

21. What formula is used to calculate the overall noise performance of the receiver or of multiple stages if RF amplification?

22. If the bandwidth is doubled, considering all other parameters unchanged except the normal thermal noise only.  The S/N will be      

23. Noise at the receiver is in terms of:

24. Reference tone level for µBa:

25. Reference tone level for dBrn:

26. Reference tone level for F1A:

27. Reliable measurement for comparing amplifier noise characteristics:

NOISE PROBLEMS

28. A receiver has noise power bandwidth of 10 kHz. A resistor that matches the receiver input impedance is connected across its antenna terminals. What is the noise power contributed by that resistor in the receiver bandwidth if the resistor has a temperature of 27 degrees Celsius?

29. A 300 ohm resistor is connected across the 300 ohm antenna input of the television receiver. The bandwidth of the receiver is 6 MHz, and the resistor is at room temperature. Find the noise power and noise voltage applied to the receiver input.

30. A diode noise generator is required to produce a 10 uV of noise in a receiver with an input impedance of 75 ohms, resistive, and a noise power bandwidth of 200 kHz. What must be the current through the diode be?

31. Two noise-source resistors R₁ and R₂ connected in series at different temperatures, 300?K and 400?K respectively. If R₁ = 100?, R₂ = 200, find:

1. the total noise voltage
2. the noise power at the load with R_L = 300?, over a BW = 100 kHz.

32. A receiver produces a noise power of 200mW with no signal. The output level increases to 5W when a signal is applied. Calculate (S+N)/N as a power ratio and in decibels.

33. The signal power at the input to an amplifier is 100 uW and the noise power is 1 uW. At the output, the signal power is 1W and the noise power is 30 mW. What is the amplifier noise figure, as a ratio? In dB?

34. The signal at the input of an amplifier has an S/N of 42 dB. If the amplifier has a noise figure of

6 dB, what is the S/N at the output in decibels?

35. An amplifier has a noise figure of 2 dB. What is the equivalent noise temperature?

36. A three-stage has stages with the following specifications: First stage with power gain and noise figure of 10 and 2 respectively, 25 and 4 for the second stage and 30 and 5 for the third stage. Find the noise temperature.

AMPLITUDE MODULATION

37. What is heterodyning?

38. What waveform is the basis of all complex waveforms?

39. What is the instantaneous amplitude of a sine wave?

40. What term describes how much of a cycle has been completed?

41. Define the heterodyne principle.

42. What is a nonlinear impedance?

43. What is spectrum analysis?

44. What two conditions are necessary for heterodyning to take place?

45. Name two methods of oscillator keying.

46. State the method used to increase the speed of keying in a CW transmitter.

47. Name a disadvantage of a single-stage CW transmitter.

48. What is the purpose of frequency- multiplier stages in a VHF transmitter?

49. What are the two major sections of a typical AM transmitter?

50. When 100 kilohertz and 5 kilohertz are heterodyned, what frequencies are present?

51. What determines the bandwidth of an AM transmission?

52. What is percent of modulation?

53. With a single modulating tone, what is the amplitude of frequencies at 100- percent modulation?

54. What is the formula for percent of modulation?

55. What is high-level modulation?

56. For what class of operation is the final rf power amplifier of a plate- modulator circuit based?

57. The modulator is required to be what kind of a circuit stage in a plate modulator?

58. How much must the fpa plate current vary to produce 100-percent modulation in a plate modulator?

59. The collector-injection modulator is similar to what type of tube modulator?

60. When is a control-grid modulator used?

61. What type of modulator is the cathode modulator (low- or high-level)?

62. What causes the change in collector current in an emitter-injection modulator?

ANGLE AND PULSE MODULATION

63. What are the two types of angle modulation?

64. Name the modulation system in which the frequency alternates between two discrete values in response to the opening and closing of a key?

65. What is the primary advantage of an fsk transmission system?

66. What characteristic of a carrier wave is varied in frequency modulation?

67. How is the degree of modulation expressed in an fm system?

68. What two values may be used to determine the bandwidth of an fm wave?

69. How does the reactance-tube modulator impress intelligence onto an rf carrier?

70. What characteristic of a transistor is varied in a semiconductor-reactance modulator?

71. What circuit section is required in the output of a multivibrator modulator to eliminate unwanted output frequencies?

72. What characteristic of a varactor is used in an fm modulator?

73. What type of modulation depends on the carrier-wave phase shift?

74. What components may be used to build a basic phase modulator?

75. Phase-shift keying is similar to what other two types of modulation?

76. Overmodulating an rf carrier in amplitude modulation produces a waveform which is similar to what modulated waveform?

77. What is prt?

78. What is nonpulse time?

79. What is average power in a pulsed system?

80. What action is necessary to impress intelligence on the pulse train in pulse modulation?

81. To insure the accuracy of a transmission, what is the minimum number of times a modulation wave should be sampled in pulse modulation?

82. What, if any, noise susceptibility advantage exists for pulse-amplitude modulation over analog-amplitude modulation?

83. What characteristics of a pulse can be changed in pulse-time modulation?

84. Which edges of the pulse can be modulated in pulse-duration modulation?

85. What is the main disadvantage of pulse-position modulation?

86. If a modulating wave is sampled 10 times per cycle with a 5-element binary code, how many bits of information are required to transmit the signal?

87. What is the primary advantage of pulse-modulation systems?

DEMODULATION

88. What is the simplest form of cw detector?

89. What principle is used to help distinguish between two cw signals that are close in frequency?

90. How does heterodyning distinguish between cw signals?

91. What simple, one-transistor detector circuit uses the heterodyne principle?

92. What three functions does the transistor in a regenerative detector serve?

93. What does the simplest diode detector use to reproduce the modulating frequency?

94. What is the function of the diode in a series-diode detector?

95. Which junction of the transistor in the common-emitter detector detects the modulation envelope?

96. How is the output signal developed in the common-emitter detector?

97. What type of tank circuit is used in the Foster-Seeley discriminator?

98. What is the primary advantage of a ratio detector?

99. What circuit functions does the tube in a gated-beam detector serve?

100. What condition must exist on both the limiter and quadrature grids for current to flow in a gated-beam detector?

101. Name two advantages of the gated-beam detector.

102. Where is the intelligence contained in a phase-modulated signal?

103. How is a quadrature detector changed when used for phase demodulation?

104. In its simplest form, what functions must a radar detector be capable of performing?
105. What characteristic of pulse does a peak detector sample?

106. What is the time constant of the resistor and capacitor in a peak detector for PAM?

MODULATION/RECEIVERS/TRANSMITTERS

107. The power output of a single-sideband transmitter is normally expressed as the power.

108. SSB modulation is classified as

109. Used to suppress carrier in single sideband transmitters.

110. Carrier is said to be overmodulated if the positive peak rises to a

a common-base detector?

value

of the maximum

111. To what circuit arrangement is a common-base detector equivalent?

unmodulated carrier.

112. Devices used to make modulated envelope visible.

113. What will be the result in balanced modulation if not perfectly balanced.

114. Advantage of series modulation

115. Filter attenuates signals, passes below and above that band.

116. To provide 2 or more voice currents with same carrier.

117. To raise the power levels of AM signals, the class of amplifier used is       .

118. Supposed a voice frequency of 400 Hz is transmitted on an AM radio station operating on 590 kHz, the voice frequency 400 Hz is NOT the

              frequency.

119. What will normal AM receiver detect from an unmodulated RF AC wave?

120. Splatter is the result of                                  .

121. What happens in standard AM transmission, no modulating signal is being transmitted?

122. B8E, form of modulation also known as

            .

123. Colloquial term describes additional side frequencies produced by overmodulation or distortion in AM.

124. Shape trapezoidal pattern at 100% modulation.

125. What is the effect if the gain level being too high for signals entering the modulator?

126. The RF signal produce; carrier frequency (fc) minus modulating frequency (fm).

127. Mixer is also known as:

128. In filter design, the maximum SB suppression is:

129. Transmitter power output in SSB operation is expressed in terms of

130. For SSB transmitter, the average power is typically of the peak envelope power, with the typical human speech.

131. Modulation system most noise resistant

132. Pre-emphasis provides extra noise immunity by

133. The three major types of demodulators:

134. In a frequency synthesizer, smallest amount which output frequency can be changed?

135. Internal capacitance, causes feedback produces same effect on…

136. Small length of wire found in some RF equipment, connected only at one end and use as a capacitance to ground.

137. Movement of signal from one frequency to another using mixer-oscillator combination.

138. Feature of modulating tone, FM deviation is proportional

139. Modulating 2 waves of the same frequency, but with          phase difference is equivalent to modulating both amplitude and phase of the same carrier.

140. Frequency of unmodulated carrier of an FM.

141. What determines stations that will be selected by a tuner?

142. Periodic waveforms consist of add harmonics.

143. Major problem with VHF oscillator.

144. What happens to a spectrum of repetitive pulse as the pulse width decrease?

145. Keyed AGC is AGC that

146. Main disadvantage of single-tube transmitter.

147. What is reduced by rounding off squarewave emission.

148. Gained by operating oscillator on some subharmonic of frequency.

149. Multiplexing, oldest and simplest.

150. Device display signal state of many lines simultaneously.

151. Most common IF carrier frequency.

152. Citizen Band (CB) Radio Service is a two-way voice communication device, it uses frequency range from                                                                 MHz.

153. What determines the rate of frequency swing for an FM broadcast transmitter?

154. In PLL demodulating an FM signal.

155. In PLL frequency modulator, f_m

156. Find the modulation index if a 10V carrier is amplitude-modulated by three different frequencies with amplitudes of 1V, 2V, and 3V, respectively.

157. Calculate the modulation index for a waveform with a maximum voltage of 150V and minimum voltage of 70V.

158. An AM broadcast transmitter has a carrier power output of 50 kW. What is the total power would be produced with 80% modulation?

159. An AM broadcast transmitter has a carrier power output of 50 kW. What is the power in one sideband with 80% modulation?

160. An AM broadcast transmiiter has a carrier power output of 50 kW. What is the total sideband power with 80% modulation?

161. An AM broadcast transmitter radiates

66 kW power when 100% modulated. If the carrier and one sideband is suppressed, how much power is save?

162. A transmitter with 10 kW carrier power transmit 12 kW when modulated with a single sine wave. When modulated with another sinewave at 50% modulation, calculate the total transmitted power.

163. The rms antenna current of a transmitter is 10 A when unmodulated, it increases by 2 A when modulated. Calculate the modulation index.

164. In SSBSC system, if the peak envelope power (PEP) is 10 W, what will be the value of the maximum instantaneous peak power?

165. In SSBSC system, if the peak voltage is 25 volts and the load resistance is 50 ohms, what will be the value of the peak envelope power (PEP)?

166. A carrier wave with an RMS voltage of

20 V and a frequency = 1.5 MHz, is modulated by a sine wave with a frequency of 500 Hz and amplitude of

10 V RMS. Determine the peak voltage of the carrier and of the lower side frequency.

167. An FM modulator has a modulator deviation constant of kf = 30 kHz/V and operates at a carrier frequency of 175 MHz. Find the output frequency instantaneous value of the modulating signal equal to -2V.

168. An FM modulator has a modulator deviation constant of kf = 30 kHz/V and operates at a carrier frequency of 175 MHz is modulated by a 3V sine wave. Calculate the deviation.

169. An FM broadcast transmitter operates at its maximum deviation of 75 kHz. Find the modulation index for a sinusoidal modulation signal with a frequency of 50 Hz.

170. A phase modulator has a phase modulator sensitivity of kp = 2 radians per volt. What RMS voltage of a sine wave would cause a peak phase deviation of 60 degrees?

171. An FM communications transmitter has a maximum frequency deviation of 5 kHz and a range of modulating frequencies from 300 Hz to 3 kHz. What is the maximum phase shift that it produces?

172. An FM communications transmitter has a maximum frequency deviation of 5 kHz and a range of modulating frequencies from 300 Hz to 3 kHz. What is the minimum phase shift that it produces?

173. A phase modulation system, has a modulation index mp = 1.5, what is maximum phase shift?

174. A phase modulator has a sensitivity of kp = 3 radians per volt. How much frequency deviation does it produces with a sine-wave input of 2V peak at a frequency of 1 kHz?

175. An FM signal has a deviation of 3 kHz and a modulating frequency of 1 kHz. Its total power is 5W, developed across a 50-ohm resistive load. The carrier frequency is 160 MHz. Using

176. An FM signal has a modulation index, mf = 3 and a modulating frequency of

2 kHz. Its total power is 5W, developed across a 50-ohm resistive load. The carrier frequency is 160 MHz. Using Carson’s rule, calculate the bandwidth of the signal.

177. An FM signal has a frequency deviation of 5 kHz and a modulating frequency of 1 kHz. The signal to noise ratio at the input to the receiver detector is 20 dB. Calculate the approximate signal-to- noise ratio at the detector output.

178. A crytal oscillator is accurate within 0.0005%. How far off frequency could be at 27 MHz?

179. A transmitter has a carrier power output of 10W at an efficiency of 70%. How much power must be supplied by the modulating amplifier for 100% modulation?

180. A transmitter operates from a 12V supply, with a collector current of 2A. The modulation transformer has a turns ratio of 4:1. What is the load impedance seen by the audio amplifier?

181. A collector modulated class C amplifier has a carrier output power Pc of 100W and an efficiency of 70%. Calculate the supply power and the transistor power dissipation with 100% modulation.

182. An AM transmitter is required to produce 10W of carrier power when operating from a 15V supply. What is the required load impedance as seen from the collector?