MULTIPLE CHOICES

QUESTIONS IN

Communications Engineering

By: S. S. Cuervo & K. L. N. Suello

400 Solved Problems

Table of Contents

Transmission Lines 65 problems solved

Radio Wave Propagation 39 problems solved

Antenna 68 problems solved

Noise 71 problems solved

Amplitude Modulation 101 problems solved

Frequency Modulation 56 problems solved

________________

Total = 400 problems solved

TRANSMISSION LINES

1. A parallel wire line spaced at 1.27 cm has a diameter of 0.21 cm. what is the

characteristic impedance?

a. 300 ohms

b. 400 ohms

c. 500 ohms

d. 600 ohms

2. In a coaxial line if the inner diameter is 0.51 cm and the center conductor has a diameter

of 0.22 cm. what is the characteristic impedance?

a. 50.1 ohms

b. 50.2 ohms

c. 50.3 ohms

d. 50.4 ohms

3. A strip line is formed using a multilayer board (dielectric constant = 2). The center track

is 0.15 inch wide and 0.005 inch thick and the PC board first layer thickness is 0.05 inch

thick, with an overall board thickness of twice the single layer. What is the characteristic

impedance?

a. 14.7 ohms

b. 14.8 ohms

c. 14.9 ohms

d. 15.0 ohms

4. In an improperly loaded transmission line, determine the power reflected from the load if

the incident power at the load is 500 W and the reflection coefficient is 0.71.

a. 252.04 W

b. 252.05 W

c. 252.06 W

d. 252.07 W

5. In wire communications system, calculate the return loss in dB, if the load impedance is

600 ohms and the characteristic impedance of the line is 300 ohms.

a. 9.52 dB

b. 9.53 dB

c. 9.54 dB

d. 9.55 dB

6. The VSWR on a loss free line of 50 ohm characteristic impedance is 4.2. Determine the

value of the purely resistive load impedance which is known to be larger than 50 ohms.

a. 210 ohms

b. 211 ohms

c. 212 ohms

d. 213 ohms

7. A micro strip line is formed using a 0.095 inch thick PC board, with a bottom ground

plane and a single 0.15 inch wide, 0.008 inch thick track on the top. What is its

characteristic impedance?

a. 72.1 ohms

b. 72.2 ohms

c. 72.3 ohms

d. 72.4 ohms

8. Determine the impedance of a balanced 2 wire with unequal diameters d1 = 12 mm and

d2 = 10 mm. the spacing between wires is 30mm.

a. 35.35 M ohms

b. 35.36 M ohms

c. 35.37 M ohms

d. 35.38 M ohms

9. For a parallel wire line, determine the conductance if the conductivity is 200 x 10-6 S/m

and the conductor diameter spacing is 10mm.

a. 1.23mS/m

b. 1.24mS/m

c. 1.25mS/m

d. 1.26mS/m

10. What is the characteristic impedance of an open line with conductors 4 mm in diameter

separated by 15 mm?

a. 241.52 ohms

b. 241.53 ohms

c. 241.54 ohms

d. 241.55 ohms

11. The forward power in a transmission line is 150 W and the reverse power is 20 W.

Calculate the SWR on the line.

a. 2.13

b. 2.14

c. 2.15

d. 2.16

12. What is the characteristic impedance of a coaxial cable using a solid polyethylene

dielectric having a relative permeability of 2.3, an inner conductor of 1 mm diameter and

an outer conductor of diameter 5mm?

a. 63.4 ohms

b. 63.5 ohms

c. 63.6 ohms

d. 63.7 ohms

13. Calculate the velocity factor of a coaxial cable used as a transmission line, with the

characteristic impedance of 50 ohms; capacitance is 40 pF/m, and inductance equal to

50microH/m.

a. 0.0745 ft

b. 0.0746 ft

c. 0.0747 ft

d. 0.0748 ft

14. What is the actual length in feet of a one quarter wavelength of a coaxial cable with a

velocity of 0.69 at 40 MHz?

a. 4.23 ft

b. 4.24 ft

c. 4.25 ft

d. 4.26 ft

15. What is the actual length in feet of one half wavelengths of a coax with velocity factor of

0.63 at 28 MHz?

a. 11.07 ft

b. 11.08 ft

c. 11.09 ft

d. 11.10 ft

16. What is the actual length in feet of one quarter wavelength of a coax with a velocity

factor of 0.68 at 39 MHz?

a. 5.577 ft

b. 5.576 ft

c. 5.575 ft

d. 5.574 ft

17. What is the actual length in feet of a one half wavelength of a coax with a velocity factor

of 0.61 at 27 MHz?

a. 11.10 ft

b. 11.11 ft

c. 11.12 ft

d. 11.13 ft

18. What is the actual length in feet of a one half wavelength of a coax with a velocity factor

of 0.59 at 26 MHz?

a. 11.16 ft

b. 11.17 ft

c. 11.18 ft

d. 11.19 ft

19. What is the actual length in feet of a one quarter wavelength of a coax with a velocity

factor of 0.695 at 42 MHz?

a. 4.05 ft

b. 4.06 ft

c. 4.07 ft

d. 4.08 ft

20. An amplifier with a 20 dB gain is connected to another with 10 dB gains by means of a

transmission line with a loss of 4 dB; if a signal with a power level of 14 dBm were

applied to the system, calculate the power output.

a. 11dBm

b. 12dBm

c. 13dBm

d. 14dBm

21. An attenuator has a loss of 26 dB. If a power of 3 W is applied to the attenuator, find the

output power.

a. 7.54mW

b. 7.55mW

c. 7.56mW

d. 7.57mW

22. What would be the approximate series impedance of a quarter wave matching line used to

match a 600 ohms feed to 70 ohms antenna?

a. 204. 94 ohms

b. 204.95 ohms

c. 204.96 ohms

d. 204.97 ohms

23. What is the impedance of a balance 4 wire with a diameter of 0.25 cm and spaced 2.5 cm

apart using an insulator with a dielectric constant of 2.56

a. 98 ohms

b. 99 ohms

c. 100 ohms

d. 101 ohms

24. What is the characteristic impedance of a single wire with diameter d = 0.25 mm placed

at the center between grounded parallel planes separated by 1 mm apart? The wire is held

by a material with a velocity factor of 0.75.

a. 71 ohms

b. 72 ohms

c. 73 ohms

d. 75 ohms

25. What is the phase coefficient of a transmission line at the frequency of 10 MHz if the

velocity of propagation is 2.5 x 108m/s?

a. 0.25rad/m

b. 0.26rad/m

c. 0.27rad/m

d. 0.28rad/m

26. Determine the conductance of a two wire open line with the following parameters; D = 4

in; d = 0.1 in. and p = 2.6 x108 ohms-m.

a. 2.75 x 10-9 S/m

b. 2.76 x 10-9 S/m

c. 2.77 x 10-9 S/m

d. 2.78 x 10-9 S/m

27. What is the input impedance of a transmission line if its characteristic impedance is 300

ohms and the load is 600 ohms? Assume a quarter wavelength sections only.

a. 149 ohms

b. 150 ohms

c. 151 ohms

d. 152 ohms

28. Determine the standing wave ratio of a 300 ohms line whose load is 400 + j150 ohms.

a. 1.67

b. 1.68

c. 1.69

d. 1.70

29. What proportion of the incident power is reflected back for the load for a 75 ohms line

terminated with ZL = 50 j25 ohms.

a. 7.82%

b. 7.83%

c. 7.84%

d. 7.85%

30. What is the attenuation of a 50 ohms coaxial cable if it has a resistance of 0.121 ohms/m?

a. 1.21 x10-3Np/m

b. 1.22 x10-3Np/m

c. 1.23 x10-3Np/m

d. 1.24 x10-3Np/m

31. Find the inductance of a 5 meter length transmission line if its characteristic impedance is

52 ohms and the capacitance is 75pF/m.

a. 1.013uH

b. 1.014uH

c. 1.015uH

d. 1.016uH

32. An open wire transmission line with a 2 mm diameter each separated by 12 mm. calculate

the characteristic impedance.

a. 297 ohms

b. 298 ohms

c. 299 ohms

d. 300 ohms

33. A coaxial cable with inner diameter of 3 mm and an outer diameter of 9 mm. determine

the characteristic impedance if the dielectric is polyethylene having ER = 2.3.

a. 43.2 ohms

b. 43.3 ohms

c. 43.4 ohms

d. 43.5 ohms

34. A coaxial transmission line uses Teflon as dielectric. What is the propagation velocity if

the signal?

a. 207 x 106 m/s

b. 208 x 106 m/s

c. 209 x 106 m/s

d. 210 x 106 m/s

35. A 530 MHz signal is propagating along a RG 8/u coaxial cable with a velocity factor

0.66. If a 75 degree phase shift is needed, what is the length if the transmission line?

a. 7.6 cm

b. 7.7 cm

c. 7.8 cm

d. 7.9 cm

36. Calculate the SWR of the line if the characteristic impedance of the line is 75 ohms and is

terminated by 50 ohms.

a. 1.4

b. 1.5

c. 1.6

d. 1.7

37. A transmitter sends a 5 W of power to a 75 ohms line. Suppose the transmitter and the

line is matched but the load is not. Determine the power absorbed by the reflection is

0.75.

a. 2.1821 W

b. 2.1822 W

c. 2.1823 W

d. 2.1825 W

38. A generator sends a 250 W of power down a line. If the SWR of the line is 2.5, determine

the power absorbed by the load.

a. 204.0 W

b. 204.1 W

c. 204.2 W

d. 204.3 W

39. A 75 ohm characteristics impedance transmission line is terminated in by a load

impedance of 120 ohms. Determine the input impedance looking into the line 1 meter

long, if the line has a velocity factor of 0.9 and operates at a frequency of 50 MHz.

a. 34.4 j12.2 ohms

b. 354 j12.2 ohms

c. 36. 4 j12.2 ohms

d. 37. 4 j12.2 ohms

40. A parallel tuned circuit is to be constructed from a shorted section of parallel wire lie. If

the operating frequency is 2.4 GHz and dielectric used is polyethylene, what is the length

of the shorted section?

a. 2.0622 cm

b. 2.0623 cm

c. 2.0624 cm

d. 2.0625 cm

41. The transmitter has an output power of 150 W. suppose the line is 50 meters long and

perfectly matched with a loss of 3 dB/100m, how much power is received in the antenna?

a. 106.1 w

b. 106.2 w

c. 106.3 w

d. 106.4 w

42. TDR equipment receives the signal 250 ns after the test signal had been transmitted. If

the discontinuity of the line is found 35 meter from the test point, what is the velocity

factor of the line?

a. 0.933

b. 0.656

c. 0.588

d. 0.2685

43. The line has 97% velocity factor. If the two minima are located 30 cm apart, determine

the frequency.

a. 485 MHz

b. 488 MHz

c. 478 MHz

d. 456 MHz

44. The power incident in the line is 20 W. assuming the reflected power is 15 W what is the

SWR of the line?

a. 1.71

b. 1.75

c. 1.25

d. 1.26

45. A transmission line 90 meter long has a characteristic impedance of 75 ohms. The line is

connected through a 15 V dc source and 75 ohms source resistance at time t = 0. What is

the voltage across the input immediately after t = 0?

a. 0 and 7.5 V

b. 1 and 2.3 V

c. 45 and 29 V

d. 69 and 56V

46. A transmission line 90 meter long has a characteristic impedance of 75 ohms. The line is

connected through a 15 V dc source and 75 ohms source resistance at time = 0. The

voltage at the input end changes to 10 V, with the same polarity as before, at time t = 1.5

micro seconds. What is the resistance that terminates the lines?

a. 465 ohms b. 896 ohms c. 563 ohms d. 150 ohms

47. A parallel wire transmission line has an inductance of 120 nH/m and a characteristic

impedance of 320 ohms. Calculate the capacitance of the line.

a. 2.25Pf/m b. 1.17pF/m c. 26.25pF/m d. 15.89pF/m

48. A radio frequency 50 ohms transmission line is connected to a coil with internal

resistance of 20 ohms and inductive reactance of 5 ohms at a frequency of 10 MHz. the

line is to be matched to the load by means of a quarter wave line and a stub that are

connected across the load. Calculate the characteristic impedance of the quarter wave

transformer.

a. 56.2 ohms

b. 32.5 ohms

c. 32.6 ohms

d. 25.3 ohms

49. An open wire line has a 3 mm diameter separated 6 mm from each other by an air

dielectric. Calculate the characteristic impedance of the line.

a. 555 ohms

b. 166 ohms

c. 584 ohms

d. 126 ohms

50. A radio frequency coaxial transmission line has a characteristic impedance of 50 ohms

and is connected across the terminals of a signal generator. The sending end voltage is 10

V. assuming that the generator, line and the load are matched; determine the current

which flows into the line.

a. 200 ma

b. 562 ma

c. 100 ma

d. 26 ma

51. A certain instrument measures the input impedance of a line and gave a reading of 1200

ohms when its far end terminals open circuited and 300 ohms when it is short circuited.

Calculate the characteristic impedance of the line.

a. 489 ohms

b. 600 ohms

c. 259 ohms

d. 546 ohms

52. A transmission line has an inductance of 253 nH/m and a capacitance of 56 pF/m. if the

physical length of the line is 1.5 m, calculate its electrical length at a frequency of 265

MHz.

a. 1.2

b. 1.4

c. 1.6

d. 1.5

53. A radio frequency transmission line has a capacitance of 46. 8 pF/m and a phase constant

of 30 degree per meter. Determine the inductance of the line at a frequency of 30 MHz.

a. 148Nh/m

b. 425nH/m

c. 165nH/m

d. 125nH/m

54. The reflected current at the load of a mismatched line is 3 mA. If the reflection

coefficient of the load is 0.7, what is the incident current?

a. 4.3 ma

b. 1.2 ma

c. 8.2 ma

d. 1.7 ma

55. A radio frequency transmission lines has a characteristic impedance of 75 ohms. If the

line is terminating by an aerial with an input impedance of 72 ohms, calculate the SWR

of the line.

a. 1.04

b. 4.02

c. 6.15

d. 2.06

56. A lossless transmission line is connected to a 10 ohms load. If the SWR = 5. Calculate

the percentage of the incident power that is dissipated in the load.

a. 89%

b. 56%

c. 15%

d. 23%

57. The reflection coefficient on a loss free line of 72 ohms characteristic impedance is 60%.

Calculate the load impedance (purely resistive) and which is smaller than 72 ohms.

a. 56 ohms

b. 18ohms

c. 45ohms

d. 12ohms

58. A radio frequency 50 ohms transmission line is connected to a coil with an internal

resistance of 20 ohms and inductive reactance of 5 ohms at a frequency of 10 MHz. the

line is to be matched to the load by means of a quarter wave line and a stub that are

connected across the load. Calculate the reactance of the stub.

a. 56.2ohms

b. 54.2ohms

c. 83.3ohms

d. 12.2ohms

59. A lossless line has 75 ohms characteristic impedance and is connected to 50 ohms load. If

the sending end current of 1 mA flows into the line. Calculate the power reflected from

the load.

a. 3uW

b. 4uW

c. 5uW

d. 6uW

60. A loss free line transmission line has an inductance of 263.2 nH/m and a capacitance of

46.8 pF/m. if the generator produces a sinusoidal voltage at 3 MHz of 2 V peak,

determine the phase change if the line is 3 meter long.

a. 23.25 degrees

b. 11.34 degrees

c. 56.12 degrees

d. 78.2 degrees

61. An AM transmitter sends a 50 W of power into a 75 ohms lossless coaxial cable. The

input impedance of the antenna at the feed point is 300 ohms. How much power is

radiated assuming unity gain, no coupling loss and the antenna is lossless?

a. 56 w

b. 87 w

c. 15 w

d. 32 w

62. A properly terminated line has a line loss of 1 dB/120m. If the power output of the

transmitter is 100 W, how much power reached the load 30 m away?

a. 12.21 w

b. 94.41 w

c. 26.18 w

d. 110.12 w

63. The output power of the transmitter is 100 W. how strong must the signal be at the

antenna if the antenna is connected to a transmission line 50 meters long with reflection

coefficient of 0.4 and an attenuation constant of 5 dB/100m?

a. 47.23 w

b. 15.12 w

c. 7893.12w

d. 154.01 w

64. A coaxial line having an impedance of 50 ohms is used in a cable TV system as drop

cable. If the maximum line voltage are 15 V and 12 V minimum. What is the SWR of the

line?

a. 4.01

b. 1.24

c. 5.23

d. 1.25

65. An SWR meter is used to measure the degree of mismatch on the line. The SWR meter

records 1.6 when the line is terminated with 50 ohms and 2.2 when the load is change to

176 ohms. What is the characteristic impedance of the line?

a. 90 ohms

b. 100 ohms

c. 80 ohms

d. 740 ohms

RADIO WAVE PROPAGATION

1. How far away is the radio horizon of an antenna 100 ft high?

a. 14.14 miles

b. 5.23 miles

c. 144.15 miles

d. 568.1 miles

2. What is the maximum line of sight distance between a paging antenna 250 ft. high and a

pager receiver 3.5 ft of the ground?

a. 26 miles

b. 25 miles

c. 21 miles

d. 23 miles

3. At a certain time, the MUF for transmissions at an angle of incidence of 75 degree is 17

MHZ. what is the critical frequency?

a. 2.32 MHz

b. 56.2 MHz

c. 4.4 MHz

d. 10.215 MHz

4. What power density is required to produce electric field strength of 100 volts per meter in

air?

a. 26.5 W/m2

b. 56.23 W/m2

c. 14.20 W/m2

d. 15.12 W/m2

5. If the critical frequency is 10 MHz in sky wave propagation, what is the best frequency to

use assuming 30 degree of radiation angle?

a. 17 MHz

b. 15 MHz

c. 16 MHz

d. 12 MHz

6. In sky wave propagation, what is the critical frequency if the maximum number of free

electrons in a certain ionosphere later is 1.5 x1012

per cubic meter?

a. 45 MHz

b. 79 MHz

c. 16 MHz

d. 11 MHz

7. In wave propagation, determine the refractive index of an ionosphere layer with 100 x

106

free electrons per cubic meter at 5 MHz frequency.

a. 1

b. 2

c. 0.3

d. 0.99

8. What is the resultant field strength between waves travelling in different paths when the

product of the antenna heights above the reflecting plane is equal to half wavelength

times the total direct distance path between the two antennas?

a. 1 V/m

b. 2 V/m

c. 0 V/m

d. 3 V/m

9. According to the Philippine Electronics Code, the maximum accumulated Permissible

Dose of 68 years old man is?

a. 456rems

b. 250rems

c. 123rems

d. 320rems

10. In a VHF mobile radio system, the base station transmits 100 W at 160 MHz frequency

using half wave dipole antenna 20 meters above ground. Calculate the field strength at a

receiving antenna at a height of 4 meters and a distance of 30 km.

a. 41.78uV/m

b. 12.02uV/m

c. 157.0uV/m

d. 65.48uV/m

11. What is the effective radiated power of a repeater with 450 W transmitting power output,

4 dB feed line loss, 6 dB duplexer loss, and 7 dB circulator loss and feed line antenna

gain of 25 dB?

a. 245.2 w

b. 1254.02 w

c. 2839.31 w

d. 15.21 w

12. A microwave transmitting antenna is 600 feet high. The receive antenna is 240 feet high.

The maximum transmission distance is?

a. 23.22 m

b. 15 m

c. 487.5m

d. 56.55 m

13. As specified by the National Committee on Radiation Protection Measurement (USA),

what would be the maximum accumulated permissible does to the whole body of a 50

year old man?

a. 160rems

b. 125rems

c. 14rems

d. 102rems

14. The total power delivered to the radiator of an isotropic antenna is 200,000 W. determine

the power density at a distance of 100 meters.

a. 2 W/m2

b. 1.59 W/m2

c. 2 W/m2

d. 459 W/m2

15. Calculate the electric field intensity in mill volts per meter at 30 kW from a 5 km source.

a. 189.74 mV/m

b. 456.20 mV/m

c. 14.21 mV/m

d. 158.0 mV/m

16. What is the index of refraction of a certain substance if a light travel through the

substance at 100 meters at a time is to 140 meters to air?

a. 2.2

b. 1.4

c. 15.2

d. 48.2

17. Determine the critical frequency value of an HF signal if its maximum usable frequency

is 7050.50 kHz at 35 degrees incidence.

a. 12.22 MHz

b. 5.775 MHz

c. 124.255 MHz

d. 789.02 MHz

18. Determine the effective radiated power of 20 kW TV broadcast transmitter whose

antenna has a field gain of 2.

a. 45kW

b. 12kW

c. 65kW

d. 80kW

19. What is the free space loss, in dB, between two microwave parabolic antennas 38

kilometer apart operating at 7 GHz?

a. 140.89 dB

b. 12.02 dB

c. 785.1 dB

d. 201.2 dB

20. In sky wave propagation, if the critical frequency is 25 MHz, what is the best frequency

to use? Assume radiation angle of 45 degree.

a. 23 MHz

b. 45.2 MHz

c. 30 MHz

d. 25 MHz

21. If the maximum number of free electrons in a certain ionosphere layer is 2 x 1012per m3,

what is its critical frequency?

a. 12.73 MHz

b. 56.2 MHz

c. 154.0 MHz

d. 21.01 MHz

22. What is the refractive index of an ionosphere layer with 100 x 105 free electrons per m3?

Assume frequency to be at 20 MHz

a. 1

b. 2

c. 0.99

d. 3

23. If the velocity of propagation in a certain medium is 200 x 106, what is its refractive

index?

a. 1.2

b. 1.5

c. 1.3

d. 1.4

24. What is the propagation velocity of a signal in a transmission line whose inductance and

capacitance are 5 micro H/m and 20 micro F/m respectively?

a. 2.02 x 103 m/s

b. 236 x 103 m/s

c. 145 x 103 m/s

d. 100 x 103 m/s

25. AGILA satellite is located 36000 km above the earths surface. Assuming free space

condition what is the path loss of the signal if the operating frequency is 3 GHz?

a. 193.07 db

b. 23.2 db

c. 489 db

d. 1256.20 db

26. A certain earth station transmitter output power is 10 kW, transmitting antenna gain 100

dBi, receiving antenna gain 75 dBi, uplink and downlink frequency of 2.4 GHz and 2

GHz, respectively. What is the received signal level at the satellite?

a. 12uW

b. 125uW

c. 45uW

d. 7.71uW

27. The two half wave dipole antennas are positioned maximum transmission and reception

of signal. If the input power at the feed point is 150 W, what is the voltage induced at the

feed point if the antennas are spaced 1 km apart and operating at 126 MHz?

a. 45.21 mV

b. 65.63 mV

c. 12 mV

d. 1254.2 mV

e.

28. A mobile radio system base station is installed 50 meters above the ground and transmits

150 W at 54 MHz if the transmitting antenna gain is 5.17, how far will the receiving

antenna be, if the antenna height is 30 m and the received field strength is 22 micro V/m.

a. 153313 m

b. 25421m

c. 125789m

d. 99856m

29. Antenna heights of transmitting and receiving antenna are found to be 20 meters and 10

meters respectively. What is the maximum distance of the two antennas if troposphere

transmission is used?

a. 12.21mi

b. 45.23mi

c. 19.55 mi

d. 65.2mi

30. The antenna is beam 30 degree above the ground for optimum transmission. Determine

the transmission range, if ionosphere transmission is used and virtual height is 200 km.

assuming, the earth is flat.

a. 89 km

b. 458 km

c. 564 km

d. 693 km

31. The antenna is beam 10 degree above the ground for optimum transmission. Determine

the transmission range, if ionosphere transmission is used and virtual height is 200 km.

a. 1604 km

b. 5986 km

c. 2015 km

d. 6453 km

32. The signal propagates in fresh water with an average conductivity of 2.5 S/m. determine

the attenuation coefficient if the relative permittivity of the medium is 65 and signal

frequency is 3 kHz.

a. 172.02 x10-3Np/m

b. 45 x10-3Np/m

c. 789 x10-3Np/m

d. 15 x10-3Np/m

33. A microwave radio link is installed on a hill 100 m high above the ground. The link is 10

km from the ground station, is set to transmit 10 W from a parabolic dish having a gain of

3000 over isotropic. Calculate the signal strength received if the height of the ground

station is 10 m operating frequency at 250 MHz.

a. 78.1 mV/m

b. 99.34 mV/m

c. 45 mV/m

d. 56.23 mV/m

34. A VHF radio is to be established via the ionosphere. Assuming the earth is flat with the

critical frequency of 5 MHz, the angle of elevation is 45 degree. Calculate the optimum

working frequency.

a. 8 MHz

b. 5 MHz

c. 6 MHz

d. 56 MHz

35. An unknown medium was used in communication system. If the characteristic impedance

of that medium is 150 ohms, what is the relative permittivity?

a. 5.23

b. 20.51

c. 2.51

d. 2.54

36. A shortwave transmitter uses sky wave propagation. What is the angle of incidence if the

MUF is 19 MHz and the critical frequency is 5 MHz?

a. 45.2

b. 15.36

c. 74.7

d. 15.25

37. What is the critical angle of the signal when it passes from glass, with relative

permittivity of 7.8 into air?

a. 7.4

b. 5.2

c. 3.2

d. 51.2

38. A TV broadcast station has a transmitting antenna located 20 m above the ground. What

is the height above the ground of the receiving antenna 30 km from the transmitter?

a. 4.5m

b. 7.9m

c. 65.2m

d. 15.25m

39. What is the angle of incidence of the radio wave signal as it moves from air to glass, if

the angle of refraction is 8.2 degree?

a. 2.93

b. 6.26

c. 8.5

d. 56.2

ANTENNA

1. Two half wave dipole antennas are positioned for optimum transmission and

reception. Calculate the open circuit voltage induced in one lambda over 2 dipole

when 20 W of power at 250 MHz is radiated from another lambda over 2 dipole 100

km away.

a. 119.32uV

b. 45.25uV

c. 78.2uV

d. 89uV

2. For an antenna in a form of a linear conductor or an array of conductors calculate the

effective length at 3 MHz.

a. 56.2 m

b. 23.5 m

c. 31.83 m

d. 56.3 m

3. To minimize interference, a 500 MHz dish needs to have a 1 degree beam width.

What is the corresponding gain in dB?

a. 56 db

b. 45.2 db

c. 48.2 db

d. 44.7 db

4. A dish designed for operation at 150 MHz is operated at twice that frequency. By

what factor do gain change?

a. 5

b. 4

c. 3

d. 2

e. 1

5. What is the power gain in dB of a uniformly illuminated parabolic reflector whose

half power beam width is 3 degrees?

a. 45.2 db

b. 33.5 db

c. 56.5 db

d. 783db

6. In aperture antennas for microwave communications, what is the aperture number if

the angular aperture is 55 degree?

a. 0.48

b. 5.2

c. 48.2

d. 12.2

7. What is the effective area of a Hertzian dipole antenna for unity efficiency at 3 MHz?

a. 1190 m2

b. 236 m2

c. 486 m2

d. 1154 m2

8. For an antenna in a form of a linear conductor, what is the effe3ctive length at 10.5

MHz?

a. 5.05

b. 2.03

c. 90.3

d. 9.09

9. A certain antenna has a gain of 7 dB with respect to an isotropic radiator. What is the

effective area if it operates at 200 MHZ?

a. 0.897 m2

b. 12 m2

c. 0.5 m2

d. 0.65 m2

10. Determine the gain of an antenna with respect to a dipole if its gain with respect to

isotropic is 50 dBi.

a. 4.5 dB

b. 47.86 dB

c. 45.25 dB

d. 96.2 dB

11. If an antenna has a length of 0.125 lambdas then what is the radiation resistance?

a. 12.34 ohms

b. 78 ohms

c. 14.23 ohms

d. 56.2 ohms

12. What is the horizontal beam width of a pyramidal horn antenna if its width is one

wave length?

a. 78

b. 23

c. 80

d. 14

13. At 2 MHz, what is the effective area of the Hertzian dipole for unity efficiency?

a. 2677.5 m2

b. 45.25 m2

c. 7855.2 m2

d. 5699 m2

14. A helical has the following dimensions; pitch is 1/3 wavelength; diameter is

wavelength and turns is 27. What is the gain in dB?

a. 45.2 dB

b. 5603 dB

c. 59.2 dB

d. 19.2 dB

15. What is the phase separation of two antennas 3/8 wavelengths apart?

a. 45

b. 56

c. 135

d. 270

16. A 400 feet antenna is to be operated at 6200 kHz. What is the wavelength at this

frequency?

a. 48.39m

b. 45.26m

c. 23.56m

d. 15.26m

17. A microwave communications uses plane reflectors as passive repeaters. The

diameter of the parabolic antenna is 18 feet while the effective area is 310 ft2.

Determine the reflector coupling factor.

a. 0.5

b. 0.6

c. 0.9

d. 0.91

18. A TVRO installation for use with a C- band satellite has a diameter of about 3.5

meters and an efficiency of 60%. Calculate its beam width.

a. 4.2

b. 1.5

c. 2.3

d. 5.2

19. A 500 kHz antenna radiates 500 W of power. The same antenna produces field

strength equal to 1.5 mV/m. if the power delivered by the antenna is increased to 1

kW, what would be the expected field intensity?

a. 2.12 mV/m

b. 45 mV/m

c. 3.13 mV/m

d. 5.2 mV/m

20. What is the effective radiated power of a repeater with 250 W transmitting power

output, 3 dB feed line loss, 4 dB duplexer loss, 5 dB circulator loss and feed line

antenna gain of 20 dB?

a. 456.2w

b. 1577.61w

c. 4599.2w

d. 7853.2w

21. What is the length in feet of an antenna wire for 5 MHz if the antenna is 3.5 waves in

length?

a. 688.8 ft

b. 563.23 ft

c. 865.23ft

d. 485.21ft

22. If the antenna current increases 3.4 times, how much does the radiated power

increase?

a. 45.2

b. 11.56

c. 89.2

d. 4.2

23. Determine the effective radiated power of a transmitter if the input power to the final

amplifier of 370 W with 60% efficiency if the field gain of the antenna is 1.3,

assuming 100% transmission line efficiency.

a. 452.1 W

b. 123.2W

c. 784.6W

d. 375.18W

24. The transmitting antenna has a gain of 10 dB, and power output of 6000 W.

determine the effective radiated power.

a. 30000W

b. 40000W

c. 50000W

d. 60000W

25. What is the approximate length of a half wave dipole antenna radiating at 6450 kHz?

a. 72.5 ft

b. 45.3ft

c. 45.8ft

d. 78.2 ft

26. Determine the approximate length of a simple whip quarter wave antenna at UHF

frequency of 450.25 MHz.

a. 0.35 ft

b. 0.15ft

c. 0.89ft

d. 0.52ft

27. What is the length if a simple quarter wave antenna using a VHF frequency of 150.

55 MHz?

a. 1.55 ft

b. 2.63ft

c. 4.25ft

d. 7.23ft

28. Find the approximate width of a pyramidal horn antenna that will operate at 10000

MHz intended to have a beam width 10 degree.

a. 26cm

b. 24cm

c. 45cm

d. 78cm

29. Determine the gain of a 6 ft parabolic dish operating at 1800 MHZ.

a. 45.12dB

b. 28.17dB

c. 12.5dB

d. 32.02dB

30. A dipole antenna requires to be feed with 20 kW of power to produce a given signal

strength to a particular distant point. If the addition of a reflector makes the same field

strength available with an input power of 11 kW. What is the gain in dB obtained by

the use of the reflector?

a. 8.5 dB

b. 4.6 dB

c. 2.6 dB

d. 1.6 dB

31. What is the gain, in dB of a helical antenna with diameter of lambda over 3, 10 turns

at pitch of lambda over 4, used at 100 MHz?

a. 18.2dB

b. 16.1dB

c. 52.3dB

d. 17.6dB

32. The frequency of operation antenna cut to length of 3.4 m.

a. 44.12 MHz

b. 45.2 MHz

c. 78.2 MHz

d. 56.8 MHz

33. What is the effective radiated power of a repeater with 200 W transmitting power

output, 2 dB feed line loss, 2 dB duplexer loss, and 3 dB circulator los and feed line

antenna gain of 10 dB?

a. 458 W

b. 398W

c. 896W

d. 126W

34. Determine the dB gain of a receiving antenna which delivers a microvolt antenna

which delivers a microvolt signal to a transmission line over that of an antenna that

delivers a 2 micro volt signal under identical circumstances.

a. -7dB

b. -8dB

c. -9dB

d. -6dB

35. The actual length of the Marconi antenna used in AM transmitter is 34 m. what is the

operating frequency of the transmitter, if the velocity factor is 0.9?

a. 5.2 MHz

b. 1.98 MHz

c. 4.2 MHz

d. 3.2 MHz

36. What is the ohmic resistance of the antenna, if the efficiency of the antenna is 0.96

and the radiation resistance is 72 ohms?

a. 1

b. 2

c. 3

d. 4

37. What is the gain of a half wave dipole antenna if the antenna has an efficiency of

92%?

a. 4.2

b. 1.3

c. 1.6

d. 1.51

38. The output power of an FM transmitter is 25 W. if the gain of the antenna referred to

isotropic is 50, what is the ERP of the antenna?

a. 85.23dBw

b. 45.23dBw

c. 89.5dBw

d. 28.83dBw

39. A satellite tracking device uses a helical antenna that is operating at 1.2 GHz. If the

optimum diameter of the antenna is 8 mc and 10 turns, what is the gain of the

antenna?

a. 42.13dB

b. 15.78dB

c. 15.6dB

d. 15.89dB

40. A helical shape antenna with eight turns is used to track satellite that is operating at

1.2 Ghz. If the spacing for the antennas is 10 cm, what is the beam width of the

antenna?

a. 28.9

b. 56.2

c. 65.3

d. 21.3

41. A certain antenna with twelve turns is used to operate at a frequency of 1.2 GHz.

What is the total length of the antenna?

a. 75 cm

b. 56cm

c. 23cm

d. 14cm

42. An earth satellite station needed an antenna that can amplify 2500 times bigger than

the input signal. If the engineers assigned agreed to build an antenna with parabolic

reflector, and operates at 3.4 GHz, what is its diameter?

a. 452 cm

b. 120cm

c. 180cm

d. 5620cm

43. Calculate the operating frequency of a half wave dipole if the actual length is 3.5

meter.

a. 40.7MHz

b. 21.3 MHz

c. 56.2 MHz

d. 58.1 MHz

44. Calculate the actual length of a half wave dipole operating at a frequency of 67.25

MHz.

a. 4.2m

b. 1.2m

c. 3.1m

d. 2.12m

45. An antenna with a radiation resistance of 50 ohms and a loss resistance of 3 ohms

receives 150 watts of power from a transmitter. How much power is radiated into

space?

a. 141.51W

b. 235.21W

c. 563.25W

d. 612.35W

46. An antenna with a radiation resistance of 75 ohms and a loss resistance of 5 ohms,

receives a 150 watts of power from a transmitter. How much power is wasted?

a. 56.2w

b. 5.35w

c. 154.2w

d. 9.375w

47. What is the efficiency of the antenna if the radiation resistance is 72 ohms and the

loss resistance is 2 ohms?

a. 89.2%

b. 97.3%

c. 56.2%

d. 100%

48. A half wave dipole with a gain of 2.14 dBi is fed, by means of lossless, matched line

by a 25 watts transmitter. What is the electric field strength of the signal measured 15

km from the antenna in free space in the direction of maximum radiation?

a. 2.34 mV/m

b. 5.23 mV/m

c. 4.56 mV/m

d. 45.26 mV/m

49. A transmitter supplied 125 watts of power to an antenna with an efficiency of 95%.

What is the power density measured at a distance of 30 km from the antenna in the

direction of maximum radiation? Assume the transmission line is lossless and

perfectly matched.

a. 10.5nW/m2

b. 11.2nW/m2

c. 21.02nW/m2

d. 13.23nW/m2

50. A dipole antenna is designed to have 94% efficiency. Determine the EIRP of this

antenna if it is fed by a 50 watts transmitter.

a. 14.52dbw

b. 16.72dbw

c. 15.72dbw

d. 18.72dbw

51. Determine the actual length of a Marconi antenna operating at a frequency of 1625

kHz.

a. 42.85m

b. 41.85m

c. 43.85m

d. 44.85m

52. A parabolic antenna used in the satellite earth station has a beam width of 3 degree. If

the antenna is operating at a frequency of 14 GHz, what is the minimum diameter of

the antenna?

a. 0.5m

b. 0.6m

c. 0.2m

d. 0.3m

53. A parabolic antenna used in the satellite earth station has beam width of 3 degree.

What is the gain of the antenna if the antenna efficiency is 85%?

a. 4256

b. 4587

c. 4567

d. 1546

54. A parabolic antenna used in the satellite earth station has a beam width of 3 degree.

Calculate the effective area of a 3 m dish with an illumination efficiency of 0.7 at 3

GHz.

a. 5.95m2

b. 6.95 m2

c. 4.95 m2

d. 8.95 m2

55. The signal field strength 10 km from the Yagi antenna in the optimum direction is 12

mV/m, and 180 degrees from the optimum direction at the same distance the field

strength is reduced to 2 mV/m. what is the front to back ratio of the antenna?

a. 14.6dB

b. 15.6dB

c. 17.6dB

d. 18.6dB

56. A Yagi antenna must be fed with 5 kW of power to produce the same field strength at

a given point as that of a half wave dipole antenna fed with 10 kW of power.

Determine the gain of the Yagi antenna relative to isotropic.

a. 4.14dB

b. 3.14dB

c. 5.14dB

d. 6.14dB

57. Two antennas are fed with equal power. If the power density measured of the antenna

under test is 2 micro W/m2 and 8 micro W/m

2 for the standard antenna. What is the

gain of the antenna under test referred to dipole if the gain of the standard antenna is

30 dBi?

a. 20.86

b. 19.86

c. 21.86

d. 22.86

58. A Yagi antenna with front to back ratio of 10 dB radiates power of 10 watts in the

opposite direction. Determine the power output of the transmitter, if the gain of the

antenna is 10 dBi?

a. 8W

b. 9W

c. 1W

d. 10W

59. The power radiated on a dipole is 2 W. if the input power to the antenna is 2.6 W and

the current fed is 2 A, calculate the ohmic resistance of the dipole.

a. 0.11 ohms

b. 1.2 ohms

c. 0.16 ohms

d. 0.15 ohms

60. The power supplied to the antenna is 5 kW. If the efficiency of the dipole is 0.7,

determine the power loss of the antenna.

a. 2.5kW

b. 3.2kW

c. 6.1kW

d. 1.5kW

61. A half wave dipole is designed to intercept maximum power at 300 MHz. calculate

the effective aperture of a half wave dipole.

a. 0.16 m2

b. 0.13 m2

c. 0.12 m2

d. 0.15m2

62. A vertical whip antenna is located in field strength of 7 mV/m. if the effective length

of the antenna is 1 m. calculate the voltage induced into the antenna.

a. 7mV

b. 5mV

c. 6mV

d. 9mV

63. An aerial that is mounted vertically is operating at 3 MHz is 100 m high. It carries a

current that varies linearly from a maximum of 10 A at the base to 0 A to the top.

Determine the effective height of the aerial.

a. 200m

b. 300m

c. 100m

d. 400m

64. A half wave dipole requires to be fed with 10 kW of power to produce 2 mV/m signal

strength 5 km from the antenna. The field strength is measured again and the result is

the same, but this time a reflector is added to the antenna and the input power is only

3 kW. What is the gain of the antenna referred to isotropic with the additional

reflector?

a. 5.37dB

b. 6.37dB

c. 98.37dB

d. 7.37dB

65. An antenna wit parabolic dish reflector has a beam width of 2 degrees and a gain of

30 dBi. Calculate the power density at a range of 5 km at an angel of 1 degree to the

direction of maximum radiation if the power radiated is 1.8 W.

a. 5.86uW/m2

b. 2.86uW/m2

c. 9.86uW/m2

d. 4.86uW/m2

66. A half wave dipole antenna is used to operate at 54 MHz. considering end effect,

what is the effective area of the antenna?

a. 5.64 m2

b. 4.64 m2

c. 9.64 m2

d. 3.64m2

67. A helical antenna is used to track satellites in space. If the antenna consists of 15

turns, spacing 15 cm, and diameter 19.1 m, what is the operating frequency of the

antenna to transmit the signal efficiently?

a. 500 MHz

b. 400 MHz

c. 300 MHz

d. 200MHz

68. A satellite earth station uses an antenna with parabolic reflector that has a gain of 30

dBi at 3.2 GHz. What is its gain if the operating frequency is changed to 21.5 GHz,

assuming the other parameters remain the same?

a. 56.55dBi

b. 59.55dBi

c. 58.55dBi

d. 46.55dBi

NOISE

1. The signal to noise ratio is 30 dB at the input to an amplifier and 27.3 dB at the

output. What is the noise temperature of the amplifier?

a. 250.1K

b. 249.4K

c. 249.5K

d. 249.6K

2. A 3 stage amplifier has the following power gains and noise figures for each stage;

Stage 1, power gain = 10, noise figure = 3; stage 2, power gain = 20, noise figure = 4,

stage 3, power gain = 30, noise figure = 5. Calculate the total noise figure.

a. 5.1dB

b. 5.2dB

c. 5.3dB

d. 5.4dB

3. An amplifier operating over a 4 MHz bandwidth has a 100 ohms input resistance. It is

operating 27 degree Celsius, has a voltage gain of 200 and has input signal of 5 micro

Vrms. Determine rms output noise signal?

a. 512uV

b. 514uV

c. 523uV

d. 515uV

4. Determine the noise current for a diode with a forward bias of 1 mA over a 100 kHz

bandwidth?

a. 0.0057uA

b. 0.0056uA

c. 0.0024uA

d. 0.0051uA

5. A transistor amplifier has a measured S/N power of 10 at its input and 5 at its output.

Calculate the transistors NF.

a. 1

b. 2

c. 3

d. 4

6. Two resistors, 5 kilo ohms and 20 kilo ohms are at 27 degree Celsius. Calculate the

thermal noise voltage for a 10 kHz bandwidth if they are in series.

a. 2.031uV

b. 2.056uV

c. 2.045uV

d. 2.035uV

7. Calculate the thermal noise voltage of the two resistors, 5 kilo ohms and 20 kilo ohms

at 27 degree Celsius if they are connected in parallel.

a. 0.91uV

b. 0.54uV

c. 0.81uV

d. 0.56uV

8. Calculate the overall noise figure referred to the input of a mixer stage that has a

noise figure if 15 dB preceded by an amplifier that has a noise figure of 6 dB and an

available power gain of 20 dB

a. 6.32dB

b. 5.32dB

c. 9dB

d. 4.32dB

9. What is the input equivalent signal to noise ratio for a receiver with a noise figure of

15 dB and an output signal noise to ratio 60 dB?

a. 45dB

b. 65dB

c. 85dB

d. 75dB

10. What is the noise level in a voice channel if the S/N is 71.25 dB? Express noise level

in pWpO?

a. 45

b. 12

c. 46

d. 42

11. If the occupied baseband of white noise test signal is 60 4028 kHz. Determine the

bandwidth ratio.

a. 35.2dB

b. 31.07dB

c. 38.1dB

d. 36.2dB

12. Calculate the equivalent noise temperature of a receiver with a noise figure of 1.5 dB.

a. 119.64K

b. 118.65K

c. 112.63K

d. 118.26K

13. What is the overall signal to noise ratio in dB of a tandem connection with the

following individual signal to noise ratio. First stage = 10 dB; second stage = 15 dB

and third stage = 20 dB?

a. 5.84dB

b. 8.48dB

c. 5.98dB

d. 5.12dB

14. If all the stages in a tandem circuit have identical signal to noise of 15 dB, then what

is the overall signal to noise ratio in dB of the connection when there are 5 stages?

a. 8.05dB

b. 8.06dB

c. 8.01dB

d. 8.02dB

15. In psophometric noise measurement, what is the psophometric noise power in pWp if

the psophometer reads 10 mV of noise voltage?

a. 0.167x10-18

b. 0.168x10-18

c. 0.166x10-18

d. 0.165x10-18

16. Determine the effective noise temperature of an antenna system at the far end of the

feed line if the effective sky noise temperature is 200 K and antenna and feed line loss

is 10.

a. 289K

b. 288K

c. 282K

d. 281K

17. An amplifier operating over a 2 MHz bandwidth has an 80 ohms input resistance. It is

operating at 27 degree Celsius, has a voltage gain of 200 and an input signal of 6

micro Vrms. Calculate the output rms noise.

a. 326.6uV

b. 327.6uV

c. 325.6uV

d. 324.6uV

18. An amplifier operating over a 5 MHz bandwidth has a 100 ohm input resistance. It is

operating at 27 degrees Celsius, has a voltage gain of 200 and an input signal of 6

micro Vrms. Calculate the output rms noise.

a. 573.5uV

b. 574.5uV

c. 575.5uV

d. 576.5uV

19. A transistor amplifier has a measured S/N power of 100 at its input and 20 at its

output. Determine the noise figure of the transistor.

a. 6.99dB

b. 6.09dB

c. 6.9dB

d. 6.89dB

20. Convert noise factor of 4.02 to equivalent noise temperature. Use 300 K for

environmental temperature.

a. 903 K

b. 904 K

c. 905 K

d. 906 K

21. When measuring a voice channel dB test point level, the meter reads -76 dBm.

Calculate the reading in dBrnCO.

a. 15

b. 16

c. 17

d. 18

22. A diode generator is required to produce 12 micro volts of noise in a receiver with an

input impedance of 75 ohms and a noise power bandwidth of 200 kHz. Determine the

current through the diode in milli amperes.

a. 398mA

b. 399mA

c. 400mA

d. 401mA

23. A 3 stage amplifier has stages with the following specifications; stage 1, power gain

is 10, noise figure is 2; stage 2, power gain is 20, noise figure is 4, stage 3, power gain

is 30, noise figure is 5. Calculate the total noise figure of the system, assuming

matched condition.

a. 3.65dB

b. 3.66dB

c. 3.67dB

d. 3.68dB

24. 2 resistors rated 5 ohms and 10 ohms are connected in series and are at 27 degree

Celsius. Calculate their combined thermal noise voltage for a 10 kHz bandwidth.

a. 0.04uV

b. 0.05uV

c. 0.06uV

d. 0.07uV

25. A transistor has a measured S/N power of 60 at its input and 19 at its output.

Determine the noise figure of the transistor.

a. 2dB

b. 3dB

c. 4dB

d. 5dB

26. A transistor amplifier has a measured S/N power of 80 at its input and 25 at the

output. Determine the noise figure of the transistor.

a. 5.04dB

b. 5.05dB

c. 5.06dB

d. 5.07dB

27. A satellite receiver has a noise figure of 1.6 dB. Find its equivalent noise temperature.

a. 132.2K

b. 131.2K

c. 130.2K

d. 129.2K

28. An amplifier with an overall gain of 20 dB is impressed with a signal whose power

level is 1 watt. Calculate the power output in dBm.

a. 40dBm

b. 45dBm

c. 50dBm

d. 55dBm

29. The signal power of the input to an amplifier is 100 micro W and the noise power is 1

microW. At the output, the signal power is 1 W and the noise power is 40 mW. What

is the amplifier noise figure?

a. 6.01dB

b. 6.1dB

c. 6.02dB

d. 6.2dB

30. A 3 stage amplifier is to have an overall noise temperature no greater than 70 degree

K. the overall gain of the amplifier is to be at least 45 dB. The amplifier is to be built

by adding a low noise first stage to an existing amplifier with existing characteristics

as follows; stage 2 has 20 dB power gain; 3 dB noise figure. Stage 3 has 15 dB power

gain and 6 dB noise figure that the first stage can have.

a. 0.56db

b. 0.66db

c. 0.76db

d. 0.86db

31. What is the effect on the signal to noise ratio of a system if the bandwidth is doubled,

considering all other parameters to remain unchanged except the normal thermal

noise only? The S/N will be?

a.

b. 1/3

c. 2/3

d. 1/4

32. Determine the shot noise for a diode with a forward bias of 1.40 mA over an 80 kHz

bandwidth.

a. 4.nA

b. 5.nA

c. 6.nA

d. 7.nA

33. Given a noise factor of 10, what is the noise figure in dB?

a. 5dB

b. 10dB

c. 15dB

d. 20dB

34. Express the ratio in decibels of power ratio 50 is to 10 Watts.

a. 6.59dB

b. 6.99dB

c. 6.79dB

d. 6.89dB

35. The resistor R1 and R2 are connected in series at 300 degrees K and 400 degrees K

temperature respectively. If R1 is 200 ohms, and R2 is 300 ohms, find the power

produced at the load over a bandwidth of 100 kHz.

a. 0.497fw

b. 0.496fw

c. 0.495fw

d. .494fw

36. If voltage change is equal to twice its original value, what is its corresponding change

in dB?

a. 4

b. 5

c. 6

d. 7

37. A 20000 ohms resistor is at room temperature. Calculate the threshold noise voltage

for a bandwidth of 100 kHz.

a. 5.657uV

b. 5.658uV

c. 5.659uV

d. 5.660uV

38. 3 amplifiers are cascaded together. Determine the total noise figure in dB if the noise

figure of each amplifier is equal to 3 dB and the amplifier gain is 10 dB each.

a. 3.24dB

b. 3.25dB

c. 3.26dB

d. 3.27dB

39. For an equivalent noise bandwidth of 10 MHz in a satellite system and a noise power

of 0.0280 pW, determine the noise density in dBW

a. -205.56dBw

b. -205.59dBw

c. -205.50dBw

d. -205.53dBw

40. 2 resistors, 20 K ohms and 50 K ohms are at ambient temperature. Calculate for a

bandwidth equal to 100 kHz, the thermal noise voltage for the 2 resistors connected in

parallel.

a. 4.78uV

b. 4.780uV

c. 4.79uV

d. 5.90uV

41. A receiver connected to an antenna whose resistance is 50 ohms has an equivalent

noise resistance of 30 ohms. What is the receivers noise temperature?

a. 174.01K

b. 174.1K

c. 174K

d. 175K

42. The equivalent noise temperature of the amplifier is 25 K. what is the noise figure?

a. 0.36dB

b. 0.41dB

c. 0.46dB

d. 0.51dB

43. The signal in a channel is measured to be 23 dB while noise in the same channel is

measured to be 9 dB. The signal to noise ratio therefore is?

a. 14dB

b. 28dB

c. 42dB

d. 56dB

44. Find the noise voltage applied to the receiver input if a 300 ohms resistor is connected

in series to a 300 ohms antenna of a television receiver.

a. 2.70uV

b. 2.7uV

c. 2.80uV

d. 2.8uV

45. A diode noise generator produces 90 nA in a receiver with an input impedance of 75

ohms, resistive and a noise power bandwidth of 250 kHz. What must the current

through the diode be?

a. 100.24mA

b. 101.24mA

c. 100.25mA

d. 101.25mA

46. 2 resistors in series (R1 = 50 ohms; T1 = 350 degree K) and (R2 = 100 ohms; T2 =

450 degree K). Determine the total noise voltage over a bandwidth of 120 kHz.

a. 543.4nV

b. 543.3nV

c. 643.4nV

d. 643.3nV

47. A certain company manufactures an AM receiver with a noise temperature of 450

degree K. calculate the noise figure of the receiver.

a. 4.0dB

b. 4.1dB

c. 4.2dB

d. 4.3dB

48. Calculate the noise temperature if the input signal to noise ratio is 20 and the output

signal to noise ratio is 5.

a. 800K

b. 870K

c. 940K

d. 1010K

49. Calculate the bias current of the diode of it produces 150 nA noise current over a 300

kHz bandwidth.

a. 234.1mA

b. 234.01mA

c. 234.2mA

d. 234.02mA

50. Noise voltage at the input of an amplifier is 1 micro V. what is the signal voltage of

the input signal to noise ratio is 20 dB.

a. 10uV

b. 100uV

c. 1000uV

d. 10,000uV

51. A receiver has a noise power of 1 nW at the input of the receiver. What would be the

signal power if the signal to noise ratio is 40 dB?

a. 5uV

b. 10uV

c. 15uV

d. 20uV

52. What would be the noise voltage generated of a 73 ohms resistor at room temperature

over the bandwidth of an FM channel?

a. 452.nV

b. 472.nV

c. 492.nV

d. 512.nV

53. A 3 stage amplifier in cascade has the following parameters. Stage 1 has a gain of 5

and noise factor 2; stage 2 has a gain of 8 and noise factor 4; stage 3 has again of 15

and a noise factor of 6. Find the overall noise factor of the system.

a. 2.725

b. 2.726

c. 2.727

d. 2.728

54. What is the noise power of a resistor at room temperature with noise bandwidth of 2.5

MHz?

a. 10x10-15w

b. 10x10-16w

c. 10x10-17w

d. 10x10-18w

55. What is the noise voltage given that R = 200 K ohms at a temperature of 27 degree

Celsius and noise bandwidth of 54 MHz?

a. 423.uV

b. 424.uV

c. 425.uV

d. 426.uV

56. Calculate the noise voltage generated by 5 kilo ohms, 10 kilo ohms and 15 kilo ohms,

resistors connected in series. Given that the temperature is 25 degree Celsius, and

noise bandwidth of 75 MHz.

a. 192.4uV

b. 193.4uV

c. 194.4uV

d. 195.4uV

57. Calculate the noise voltage generated by 3 kilo ohms, 10 kilo ohms, 21 kilo ohms,

resistors connected in parallel. Given that the temperature is 17 degree Celsius, and

noise bandwidth of 15 MHz.

a. 21.3uV

b. 21.03uV

c. 22.3uV

d. 22.03uV

58. The shot noise current on a diode is 25 nA if 2.5 mA direct current is flowing thru it.

What is the effective noise bandwidth of the diode?

a. 781.24khz

b. 781.25khz

c. 782.24khz

d. 782.25khz

59. A radio receiver uses a single parallel tuned circuit, designed to resonate at 1605 kHz.

The Q factor of the receiver is 50 and the channel bandwidth is limited to 10 kHz.

What is the noise voltage of the receiver at the input at room temperature if the

capacitance of the tuned circuit is 20 pF?

a. 0.9uV

b. 0.8uV

c. 0.7uV

d. 0.6.uV

60. A mixer with input resistance of 300 ohms has equivalent noise resistance of 100

ohms. What is the noise voltage at the input when the effective noise bandwidth is 25

kHz, the source voltage is 2 micro V and with internal resistance of 20 ohms?

a. 0.217uV

b. 0.218uV

c. 0.219uV

d. 0.220uV

61. In a TVRO circuit the antenna is connected directly into the amplifier. To match the

input impedance of the antenna and the 15 K ohms input resistance of the amplifier a

coupling system is used with 10:1 ratio. The amplifier has an equivalent noise

resistance of 150 kilo ohms. What is the noise voltage seen at the amplifiers input

terminal? Given that the effective noise bandwidth is 20 kHz at room temperature.

a. 7.0uV

b. 7.1uV

c. 7.2uV

d. 7.3uV

62. A mixer with input resistance of 200 ohms has an equivalent noise resistance of 100

ohms. What is the S/N at the input if the effective noise bandwidth is 25 kHz, a

source voltage of 2 micro V and with internal resistance of 20 ohms?

a. 18.46dB

b. 18.47dB

c. 18.48dB

d. 18.49dB

63. What is the effective noise bandwidth of a parallel tuned circuit with 5 kilo ohms and

250 nF?

a. 800hz

b. 600hz

c. 400hz

d. 200hz

64. What is the effective noise bandwidth of a parallel resonant circuit that has a Q factor

of 100 and resonant frequency of 5 MHz?

a. 78.54khz

b. 78.55khz

c. 78.56khz

d. 78.57khz

65. A parallel tuned circuit with 20 pF tuning capacitor has an effective noise bandwidth

of 15 kHz. What is the noise voltage across the circuit at room temperature if the

resonant frequency is 5 MHZ and a Q factor of 50?

a. 4.4uV

b. 4.04uV

c. 4.5uV

d. 4.05uV

66. In a TVRO circuit the antenna is connected directly into the amplifier. To match the

input impedance of the antenna and the 15 kilo ohms input resistance of the amplifier

a coupling system is used. The amplifier has an equivalent noise voltage of 7.1 micro

V at the input. Determine the antenna EMF to produce an S/N of 30 dB if the

transformer coupling has a turns ratio of 10:1. Given that the effective noise

bandwidth is 20 kHz at room temperature.

a. 44.8uV

b. 44.9uv

c. 44.10uV

d. 44.11uV

67. 4 telephone circuits are connected in tandem. What is the overall S?N ratio of each

circuit has a S/N of 30 dB.

a. 12dB

b. 24dB

c. 36dB

d. 48dB

68. What is the output S/N ratio if the noise factor is 20 and 25 dB input S/N ratio?

a. 6324.56

b. 6325.56

c. 6326.56

d. 6327.56

69. An AM receiver with RF amplifier, mixer and an AF amplifier has an overall noise

figure of 60. The mixer has a noise factor of 20 and power gain of 30, and AF

amplifier has noise factor and power gain of 30 and 50 respectively. What is the noise

factor of the RF amplifier if their power gain is 50?

a. 59.5

b. 59.6

c. 59.7

d. 59.8

70. A TVRO parabolic dish reflector mixer stage has a noise figure of 20 dB and is

preceded by an LNB with a power gain of 10 dB and an equivalent noise temperature

of 60 degree K. what is the effective noise temperature at the input of LNB?

a. 2921K

b. 2931K

c. 2941K

d. 2951K

71. In a microwave communications system, determine the noise power in dBm for an

equivalent noise bandwidth of 10 MHz.

a. -103.98dBm

b. -103.97dBm

c. -103.96dBm

d. -103.95dBm

AMPLITUDE MODULATION

1. Determine the power saving in percent when the carrier is suppressed in an AM

signal modulated to 80%.

a. 75.76%

b. 75.77%

c. 75.78%

d. 75.79%

2. Find the percent of modulation of an AM signal if 8 V signal carrier is modulated by

3 different frequencies with amplitude 1 V, 2 V and 3 V

a. 46.8%

b. 46.9%

c. 47.8%

d. 47.9%

3. An SSB transmitter radiates 100 W in a 75 ohms load. The carrier signal is modulated

by 2 tones, with frequencies 2 kHz and 3 kHz wit equal magnitude and only the lower

sideband is transmitted with a suppressed carrier. What is the peak voltage across the

load?

a. 122.5V

b. 122.6V

c. 122.7V

d. 122.8V

4. An AM transmitter delivers 100 W carrier powers, when the supplies deliver 10 A

from a 15 V. what load impedance is required by this amplifier in order for it to

deliver the rated power?

a. 1.24ohms

b. 1.25ohms

c. 1.26ohms

d. 1.27ohms

5. In AM, what is the sideband power percentage assuming 100% modulation and with

carrier total power of 100 W and 150 W respectively.

a.

b. 1/3

c.

d. 2/3

6. An AM receiver uses a double tuned IF transformer with coupling constant of 1.5 kc.

the quality factor of the primary and secondary winding is 60 and 30 respectively.

What is the bandwidth of the transformer if the IF is 455 MHz?

a. 16.38khz

b. 16.37khz

c. 16.36khz

d. 16.35khz

7. A measure of steepness of the skirts or the skirt selectivity of a receiver is the shape

factor. What is the shape factor of a receiver whose 60 dB bandwidth is 12 kHz and a

6 dB bandwidth of 3 kHz?

a. 2

b. 4

c. 6

d. 8

8. A 200 V without modulation and 250 V with modulation is measured across a 50

ohms resistive load using true RMS reading meter. What is the overall efficiency

without modulation if the transmitter draws 1 kW of power from the ac line?

a. 60%

b. 70%

c. 80%

d. 90%

9. An Am transmission of 3 kW is 100% modulated. If it is transmitted as an SSB

signal, what would be the power transmitted?

a. 500W

b. 1000W

c. 1500W

d. 2000W

10. The dc power supply of an SB transmitter is 24 V. what is the average power if the

transmitter if on voice peaks the current achieves a maximum of 9.3 A?

a. 74.4W

b. 74.5W

c. 74.6W

d. 74.7W

11. An AM receiver is tuned to broadcast station at 600 kHz. Calculate the image

rejection in dB, assuming that the input filter consists of one tuned circuit with a Q of

40.

a. 37.57dB

b. 38.57dB

c. 39.57dB

d. 40.57dB

12. An SSB system transmits a peak envelope power of 100 W into a 75 ohms load. The

carrier signal is modulated by two tones, with frequencies 2 kHz and 3 kHz with

equal magnitude and only the lower sideband is transmitted with a suppressed carrier.

Determine the average power into the load.

a. 25W

b. 50W

c. 75W

d. 100W

13. In the SSB, determine the maximum suppression of the unwanted sideband if the

deviation from a perfect 90 degree phase shift is 5 degree?

a. 27.2dB

b. 27.3dB

c. 27.4dB

d. 27.5dB

14. An AM transmitter has an output power of 100 W at no modulation with efficiency of

60%. What will be the output power with 97% modulation?

a. 147W

b. 148W

c. 149W

d. 150W

15. A standard AM receiver is tuned to a station at 650 kHz. If the intermediate frequency

of the receiver is 455 kHz, what is the image frequency?

a. 1550khz

b. 1560khz

c. 1570khz

d. 1580khz

16. An AM signal has a carrier frequency of 400 MHz and amplitude if 5 Vp. It is

modulated by a sinusoidal wave with frequency of 2 kHz and peak amplitude of 2 Vp.

What are the lower and upper sideband frequencies?

a. 300.002mhz

b. 400.002mhz

c. 500.002mhz

d. 600.002mhz

17. Given an audio power of 500 W which will modulate an RF amplifier to 50%

modulation. Find the Dc power input.

a. 1000W

b. 2000W

c. 3000W

d. 4000W

18. A CB transmitter supplies a total power of 120 W to an aerial. Suppose the carrier is

amplitude modulated to a depth of 80%, how much power is wasted by the carrier

signal?

a. 31W

b. 61W

c. 91W

d. 121W

19. An IF transformer of a radio receiver operates at 455 kHz. The primary circuit has a

Q of 50 and the secondary has a Q of 40. Find the bandwidth using the optimum

coupling factor.

a. 15.288khz

b. 30.288khz

c. 45.288khz

d. 60.288khz

20. A spectrum analyzer is used ti measure the magnitude of a certain signal with respect

to its frequency. Suppose the equipment shows a carrier at 12 dBm, with two

sidebands 8 dB below the carrier, what is the depth of modulation of the signal?

a. 0.6

b. 0.7

c. 0.8

d. 0.9

21. Determine the modulation index of the signal given the following parameters. Emax

= 10 Vp, Emin = 4 Vp.

a. 0.67

b. 0.68

c. 0.69

d. 0.70

22. A DSB-SC system must suppress the carrier by 50 dB for its original value of 10 W.

To what value must the carrier be reduced?

a. 0

b. 0.1

c. 1

d. 2

23. An SSBSC signal is modulated with two audio tones having frequencies of 1200 and

2700 Hz. The receiver is mistuned so that the BFO is at 2.9993 MHz. What will be

the output frequencies of the detector if the signal is LSB and the IF of the receiver is

3 MHz?

a. 350hz

b. 700hz

c. 1050hz

d. 1400hz

24. A transistor has a power dissipation rating of 30 W. assuming that the transistor is the

only element that dissipated power in the circuit, calculate the power an amplifier,

using this transistor, could deliver the load if it operates as class A with an efficiency

of 30%.

a. 12.86W

b. 12.85W

c. 12.84W

d. 12.83W

25. An Am signal supplies 150 W of carrier power when it is modulated by a single sine

wave to a depth of 70%. Suppose the total transmitted power increases by 10% when

another sine wave simultaneously amplitude modulates the carrier, determine the

modulation index of the second sine wave.

a. 0.5

b. 0.4

c. 0.3

d. 0.2

26. What rms current must a wire carry to deliver an average power if 500 W to a 4 ohm

loudspeaker?

a. 9.18A

b. 10.18A

c. 11.18A

d. 12.18A

27. A superheterodyne receiver has an IF of 455 kHz and is experiencing image channel

interference on a frequency of 1570 kHz. The receiver is tuned to?

a. 200khz

b. 400khz

c. 600khz

d. 800khz

28. An AM transmitter with a 100 kW carrier transmits 123 kW when two tones

modulated. Calculate the modulation index of the second sine wave if the total

transmitted power is 110 when modulated by a single sine wave.

a. 0.545

b. 0.546

c. 0.547

d. 0.548

29. When measuring the selectivity of a receiver, you discover that a signal level of 450

microV on an adjacent channel is required to give the same output as 1 microV signal

on the channel to which the receiver is tuned. Calculate the adjacent channel

selectivity in dB.

a. 212dB

b. 159dB

c. 106dB

d. 53dB

30. A 300 V without modulation and 350 V with modulation are measure across a 50

ohms resistive load using true RMS reading meter. What is the amount of power

supplied in the transmitter when modulated if the efficiency os 60%.

a. 4083.33W

b. 8083.33W

c. 12,083.33W

d. 16,083.33W

31. A transistor RF amplifier is required to produce 15 W of carrier power when

operating from a 12 V supply. What is the load impedance as seen from the collector?

a. 16.8ohms

b. 12.8ohms

c. 8.8ohms

d. 4.8ohms

32. The output of a power amplifier if an AM transmitter is 50 W with an efficiency of

60% and is collector modulated. How much audio power is required to be supplied to

this stage for 100% modulation?

a. 42.65W

b. 41.65W

c. 40.65W

d. 39.65W

33. The values of Vmax and Vmin as read from an AM wave on an oscilloscope are 2.6

and 0.29 respectively. Determine the percentage modulation.

a. 79.9%

b. 69.9%

c. 59.9%

d. 49.9%

34. A 3 stages RF amplifier of an AM transmitter has an output power of 25 kW. What is

the power supplied at the second stage if the gain of the last stage is 10 dB?

a. 2.5W

b. 5W

c. 7.5W

d. 10W

35. An AM transmitter supplies a 10 kW of carrier power to a 50 ohms load. It operates

at a carrier frequency of 1.2 MHz and is 85% modulated by a 3 MHz sine wave.

Calculate the RMS voltage of the signal.

a. 825V

b. 1650V

c. 2475V

d. 3300V

36. An AM signal has a modulation carrier power if 10 watts. The percentage of

modulation is 90%. The total sideband power is?

a. 4.05W

b. 4.06W

c. 4.07W

d. 4.08W

37. A class C amplifier has a carrier output power of 100 W and an efficiency of 75%,

when operating from a 20 V supply. If the audio power is 25 W, what is the

impedance seen looking into the power amplifier from the modulation transformer

secondary?

a. 8

b. 16

c. 24

d. 32

38. An AM signal has the following characteristics; carrier frequency = 150 MHz;

modulating frequency = 3 MHz; peak carrier voltage = 40 V and peak modulation

voltage = 30 V. calculate the peak voltage of the lower sideband frequency.

a. 15V

b. 30V

c. 45V

d. 60V

39. An AM signal has a carrier frequency of 3 MHz and amplitude of 3 Vpeak. What is

the amplitude of the sidebands if the modulation index is 0.6?

a. 0.9V

b. 1.0V

c. 1.1V

d. 1.2V

40. An Am transmitter has an output power of 30 kW. If the last stage of the RF amplifier

has a gain of 20 dB and an efficiency of 75%, how much current does the amplifier

draw from a 125 V supply?

a. 160mA

b. 320mA

c. 480mA

d. 640mA

41. A receiver has two uncoupled tuned circuits before the mixer, each with a Q of 75.

The signal frequency is 100.1 MHz and IF is 10.7 MHz. if the local oscillator uses

high side injection, what is the image rejection ratio on dB?

a. 29.33dB

b. 29.66dB

c. 29.99dB

d. 30.33dB

42. An amplitude signal has a maximum positive envelope voltage of 14 V and a

minimum of 2 V. what is the total transmitted power if the carrier power is 10 kW

and suppressing one of the sidebands?

a. 10.41kW

b. 11.41kW

c. 12.41kW

d. 13.41kW

43. The average collector current of a transistor RF amplifier operating class C is 250

mA. If the efficiency of the amplifier is 50% and operating at 50 V supply, how much

audio power is needed for 100% modulation?

a. 3.25W

b. 6.25W

c. 9.25W

d. 12.25W

44. A radio transmitter has to operate at a temperature of 34 degrees Celsius. If its signal

is derived from a crystal oscillator with a temperature coefficient of plus 1 pm per

degree centigrade and it transmits at exactly 150 MHz at 20 degrees centigrade, find

the transmitting frequency.

a. 150.0021 MHz

b. 160.0021 MHz

c. 170.0021 MHz

d. 180.0021 MHz

45. A standard AM radio can receive signal from 565 1650 kHz. If an AM receiver is

tuned at 854 kHz, what is the frequency of the image signal?

a. 1564 kHz

b. 2356 kHz

c. 1764 kHz

d. 1587 kHz

46. An AM transmitter is modulated by two sine waves at 1.5 kHz and 2.5 kHz, with

modulations of 20% and 80% respectively. Calculate the effective modulation index.

a. 0.26

b. 0.45

c. 0.84

d. 0.82

47. Calculate the power in one sideband of an AM signal whose carrier power is 50 watts.

The unmodulated current is 2 A while the modulated current is 2.4 A

a. 15W

b. 14W

c. 16W

d. 11 W

48. An AM broadcast transmitter has a sideband power output of 5 kW. Calculate the

carrier power if the modulation index is 0.5.

a. 45kW

b. 40kW

c. 56kW

d. 52kW

49. If a transmitters supplies 8 kW to the antenna when it is unmodulated, determine the

total radiated power when modulated at 30%.

a. 8.36kW

b. 5.23kW

c. 8.21kW

d. 2.56kW

50. An LC tuned circuit is used to detect an AM radio frequency band ranging from 535

to 1695 kHz. What us the bandwidth at 1695, if its bandwidth is 12 kHz at 535 kHz?

a. 45.65 kHz

b. 34.21 kHz

c. 21.36 kHz

d. 56.23kHz

51. A class C collector modulated amplifier has an output carrier power of 100 W and an

efficiency of 80%. How much audio power must be supplied to the amplifier for

100% modulation?

a. 62.5W

b. 26.3W

c. 59.2W

d. 12.2W

52. What is the range of the upper sideband of an amplitude modulated signal whose

carrier is 2.5 MHz and the intelligence component is 50 Hz to 20 kHz?

a. 5.23 MHz

b. 2.52 MHz

c. 23.2 MHz

d. 1.23MHz

53. An SSB transmitter generates USB signal with Vpeak = 10 V. determine the peak

envelope power across a 50 ohms load resistance.

a. 1W

b. 2W

c. 3W

d. 7W

54. CB radio wave signal is developed using a full carrier DSB-AM. For high fidelity, the

system requires a frequency response from 50 Hz to 15 kHz. What bandwidth would

it used to satisfy the requirement?

a. 35 kHz

b. 32 kHz

c. 30 kHz

d. 31kHz

55. The frequency response of an audio signal that amplitude modulates the carrier signal

is 6 dB down at 2.5 kHz deom its level at 1.25 kHz. What will be the modulation

index due to a 2.5 kHz signal with the same signal at the input, if a 1.25 kHz signal

modulates the carrier to 85%?

a. 0.236

b. 0.425

c. 12.033

d. 0.569

56. In an AM transmitter, the final RF power amplifier is high level modulated. The dc

supply voltage is 48 V with a total current of 3.5 A. how much AF power is required

for 100% modulation?

a. 48W

b. 84W

c. 56W

d. 23W

57. An AM transmitter supplies of 20 kW of carrier power to a 75 ohms load. Calculate

the maximum instantaneous voltage the will be developed across the load.

a. 1546V

b. 5642V

c. 1722V

d. 1732V

58. What is the peak envelope power of a SSB transmitter that produces a peak to peak

voltage of 178 V across a 75 ohms antenna load?

a. 56.2W

b. 52.8W

c. 62.5W

d. 63.2W

59. What oscillator frequency is needed to heterodyne 626 kHZ up to 3.58 MHz?

a. 4.206 MHz

b. 2.036 MHz

c. 5.021 MHz

d. 3.021MHz

60. An SSB system requires 100 W of transmitted power fir reliable transmission. How

much power is needed if DSBFC is used instead of SSB?

a. 500W

b. 600W

c. 700W

d. 800W

61. A carrier signal simultaneously modulated by two sine waves at 1.5 kHz and 0.8 kHz

with modulation index 0.3 and 0.6 respectively. Calculate the total modulation index.

a. 0.32

b. 0.67

c. 0.25

d. 0.87

62. A CB transmitter supplies a total power of 200 W to an aerial. Supposed the carrier is

modulated to a depth of 70% using DSBFC AM. By how much will the signal to

noise ratio be improved if the modulation technique used is SSB instead of DSBFC

AM?

a. 10dB

b. 11dB

c. 12dB

d. 13dB

63. What is the power in one sideband of an AM signal whose carrier is 300 W, with 80%

modulation?

a. 45W

b. 46W

c. 48W

d. 12W

64. A filter type SSB generator uses an ideal band pass filter with a center frequency of 5

MHz and a bandwidth of 2.7 kHz. What frequency should be used for the carrier

oscillator if the generator is to produce a USB signal with a baseband frequency

response having a lower limit of 280 Hz?

a. 4.99837 MHz

b. 5.23154 MHz

c. 3.21548 MHz

d. 7.26456 MHz

65. What will be the total sideband power of the AM transmitting station whose carrier

power is 1200 W and a modulation of 95%?

a. 125.2W

b. 541.5W

c. 154.2W

d. 985.02W

66. An AM signal has a carrier frequency of 115 MHz modulated by a single sine wave.

The modulated signal developed a maximum positive envelope voltage of 8 V and a

minimum of 2 V. what is the magnitude of the peak voltage of the unmodulated

carrier?

a. 1V

b. 2V

c. 3V

d. 5V

67. A transistor RF power amplifier operating class C is designed to produce 40 W output

with a supply voltage of 60 V. if the efficiency is 70% what is the average collector

current?

a. 952.4mA

b. 895.3mA

c. 784.6mA

d. 896.2mA

68. A radio technician measure 350 V without modulation and 400 V with modulation at

the output of an AM transmitter with 50 ohms resistive load using true RMS reading

meter. What is the modulation index of the signal?

a. 0.56

b. 0.78

c. 0.65

d. 0.98

69. A certain amateur radio station is tuned a t200 kHz with an image frequency at 460

kHz. Determine the intermediate frequency of the receiver.

a. 150 kHz

b. 140 kHz

c. 130 kHz

d. 160kHz

70. What is the local oscillator frequency range in commercial AM broadcast if it is equal

to 455 kHz?

a. 2055 kHz

b. 2065 kHz

c. 2045 kHz

d. 2068 kHz

71. A super heterodyne receiver tunes at the frequency range from 25 to 50 MHz. what is

the IF frequency of the receiver if the range of the local oscillator is 10 MHz to 35

MHz.

a. 16 MHz

b. 15 MHz

c. 14 MHz

d. 13MHz

72. A receiver has a sensitivity of 0.5 micro V and a blocking dynamic range of 70 dB.

What is the strongest signal that can be present along with a 0.5 micro V signal

without blocking taking place?

a. 1.56mV

b. 1.53mV

c. 1.54mV

d. 1.58mV

73. A receiver can handle a maximum signal level of 100 mV without overloading is 100

dB, what is the sensitivity of the receiver?

a. 1uV

b. 2uV

c. 3uV

d. 4uV

74. What is the shape factor of the filter if 10 kHz bandwidth is measured below 6 dB and

30 kHz below 60 dB?

a. 3

b. 4

c. 5

d. 6

75. An AM transmitter uses high level modulation. The RF power amplifier draws 12 A

from a 22 V supply, putting out a carrier power of 140 watts. What impedance would

be seen at the modulation transformer secondary?

a. 1.23 ohms

b. 1.83 ohms

c. 1.56 ohms

d. 1.82ohms

76. Calculate the highest and lowest frequencies for a sub carrier signal at 629 kHz with

bandwidth of + or 500 kHz.

a. 126 kHz

b. 125 kHz

c. 124 kHz

d. 129 kHz

77. A tuned transformer has a kopt = 1.5 kc operating at a frequency of 455 kHz. The

primary of Q is 75. What is the band width of the tuned transformer?

a. 13.3 kHz

b. 14.5 kHz

c. 12.5 kHz

d. 16.3 kHz

78. A 12 W of power is being supplied in the modulating amplifier for 100% modulation.

What is the carrier power output of the radio transmitter at an efficiency of 75%?

a. 15W

b. 18W

c. 19W

d. 20W

79. A transmitted signal 5 meters in wavelength is received by an antenna coil having a

50 ohm resistance and a 0.01 H inductance. What is the capacitance of the tuner

shunting the antenna coil at this point?

a. 0.704fF

b. 0.705fF

c. 0.506fF

d. 0.404fF

80. Assuming 100% modulation, what would be the transmitted power in the upper

sideband of an AM signal if the carrier power is 1000 watts?

a. 150W

b. 250W

c. 650W

d. 350W

81. A certain radio transmitter has a carrier power output of 150 W and an efficiency of

80%. How much power is dissipated in the transistor with 80% modulation?

a. 50W

b. 56W

c. 49.3W

d. 49.5W

82. An AM transmitter uses a high level modulation. The RF power amplifier runs from a

12 V source, putting out a carrier power of 85 W, with an efficiency of 85%, what

load impedance is required in order for it to deliver the rated power?

a. 0.85

b. 0.84

c. 0.86

d. 0.89

83. An AM mobile transmitter supplies 5 kW of carrier power to a 50 ohms load. The

carrier signal is modulated by a 3 kHz sine wave to a depth of 80% at a frequency of

10 MHz. determine the sideband power.

a. 1600W

b. 1200W

c. 1500W

d. 1800W

84. If the percentage modulation of an AM amplifier is 88% and the modulating signal is

1 V, the carrier has amplitude of?

a. 1.12V

b. 1.13V

c. 1.15V

d. 1.14V

85. An AM receiver uses a low side injection for the locas oscillator, with an IF of 455

kHz. The local oscillator is operating at 2.1 MHz. What is th e IF of the signal?

a. 1.645 MHz

b. 1.256 MHz

c. 1.459 MHz

d. 1.256MHz

86. An AM signal has the following characteristics, the carrier frequency is 150 MHz, the

modulating signal frequency is 3 kHz, the carrier voltage is 60 V, and where the

modulating signal voltage is 30 V. find the peak voltage of the lower side frequency.

a. 16V

b. 15V

c. 12V

d. 13V

87. The average collector current of a transistor RF amplifier operating class C is 250

mA. If the efficiency of the amplifier is 60% and operating at 50 V supply, what is

the power output of the amplifier?

a. 5.5W

b. 6.5W

c. 7.5W

d. 8.5W

88. An AM transmitter is rated 100 W at 100% modulation. How much power required

for the carrier?

a. 66.67W

b. 55.57W

c. 44.57W

d. 99.67W

89. An AM mobile transmitter supplies 5 kW of carrier power to a 50 ohms load. The

carrier signal is modulated by a 3 kHz sine wave to a depth of 80% at a frequency of

10 MHz. Determine the peak voltage of the modulating signal.

a. 548.2V

b. 548.7V

c. 565.7V

d. 585.1V

90. An AM signal has a carrier frequency of 3 MHz and amplitude of 2 Vpeak. What is

the sideband frequency if the bandwidth of the AM signal is 20 kHz?

a. 3.02 MHz

b. 5.23 MHz

c. 1.25 MHz

d. 6.31 MHz

91. At 100% modulation, the sum of the effective voltages in both sidebands is equal to?

a. 50.2%

b. 60.2%

c. 70.7%

d. 80.5%

92. An AM transmitter transmits 40 kW with no modulation. How much power will it

transmit if modulation index increases by 80%?

a. 52.8kW

b. 56.2kW

c. 53.8kW

d. 54.6kW

93. 100% modulation in AM means a corresponding increase in total power by?

a. 60%

b. 70%

c. 50%

d. 80%

94. An AM transmitter delivers 100 W carrier powers, when the supplies deliver 8 A

from a 15 V. how much power must be supplied by the modulating amplifier 85%

modulation?

a. 45W

b. 23.5W

c. 12.4W

d. 43.35W

95. A collector modulated class C amplifier has a carrier output power of 100 W, and

with an efficiency of 60%, calculate the transistor power dissipation, assuming that all

the power dissipation that occurs comes from the transistor.

a. 66.67W

b. 65.63W

c. 689.23W

d. 68.32W

96. An AM transmitter transmits 40 kW with no modulation. How much power will it

transmit if modulation index is 80%?

a. 52.8kW

b. 52.3kW

c. 52.4kW

d. 52.9kW

97. A filter type SSB generator uses an ideal band pass filter wit h a center frequency of 5

MHz and a bandwidth of 2.7 kHz. What frequency should be used for the carrier

oscillator if the generator is to produce a USB signal with a baseband frequency

response having a lower limit of 280 Hz?

a. 4552.35 kHz

b. 4998.37 kHz

c. 4557.65 kHz

d. 4875.56kHz

98. The voice signal is modulated using a SSBSC technique with two audio tones having

frequencies of 700 and 1200 Hz. The modulated signal has a suppressed carrier

frequency in the IF receiver of 3 MHz. the receiver is mistuned causes the BFO to

generate 2.995 MHz. Determine the output frequencies of the demodulator if the

signal is USB.

a. 200 and 700 Hz

b. 300 and 800 Hz

c. 400 and 900 Hz

d. 500 and 1000Hz

99. 3 audio waves with 100, 200 and 300 V amplitude respectively, simultaneously

modulate a 450 V carrier. What is the total percent of modulation of the AM wave?

a. 86%

b. 85%

c. 84%

d. 83%

100. An AM broadcast transmitter output power is 15 kW if the carrier is

simultaneously modulated with another sine wave at 50% modulation. What is the

modulation index of the other sine wave if the carrier power is 12 kW?

a. 0.5

b. 0.2

c. 0.6

d. 0.4

101. What is the maximum suppression for a phase error of 3 degree?

a. 31.64dB

b. 31.65dB

c. 31.62dB

d. 31.52dB

FREQUENCY MODULATION

1. Using Carsons rule, what is the bandwidth of an FM signal with 5 kHz maximum

frequency deviation and 2.5 kHz maximum modulating frequency?

a. 14 kHz

b. 16 kHz

c. 18 kHz

d. 15kHz

2. Calculate the maximum bandwidth required of a standard FM broadcast station.

a. 156 kHz

b. 180 kHz

c. 154 kHz

d. 160 kHz

3. The operating frequency of an FM transmitter is 168.96 MHz. calculate the

frequency of the carrier crystal oscillator if it uses three frequency multipliers a

doubler, a tripler and a quadrupler.

a. 7.04 MHz

b. 7.05 MHz

c. 7.06 MHz

d. 7.07MHz