CHAPTER 1 Transmission Fundamentals

8/16/2019 CHAPTER 1 Transmission Fundamentals

1/25

CHAPTER 1

Transmission Fundamentals

1.

What is the opposition to the transfer of energy which is considered the dominant characteristics of a cable or

circuit that emanates from its physical structure?

A.

ConductanceB. Resistance

C.

Reactance

D. Impedance

2. When load impedance equals to ZO of the line, it means that the load _____ all the power.

A.

reflects

B. absorbs

C. attenuates

D. radiates

3. Impedance matching ratio of a coax balun.

A. 1:4

B.

4:1

C. 2:1

D. 3:2

4. Which stands for dB relative level?

A.

dBrn

B. dBa

C. dBr

D. dBx

5. Standard test tone used for audio measurement.

A. 800 Hz

B.

300 HzC.

100 Hz

D. 1000 Hz

6. When VSWR is equal to zero, this means

A. that no power is applied

B. that the load is purely resistive

C. that the load is pure reactance

D. that the load is opened

7.

_____ is the ratio of reflected voltage to the forward travelling voltage.

A. SWR

B. VSWR

C.

Reflection coefficient

D.

ISWR


2/25

8.

Transmission line must be matched to the load to _____.

A. transfer maximum voltage to the load

B. transfer maximum power to the load

C. reduce the load current

D.

transfer maximum current to the load

9.

Which indicate the relative energy loss in a capacitor?A. Quality factor

B.

Reactive factor

C. Dissipation factor

D. Power factor

10.

What is the standard test tone?

A. 0 dB

B. 0 dBW

C. 0 dBm

D.

0dBrn

11. The energy that neither radiated into space nor completely transmitted.

A.

Reflected waves

B. Captured waves

C. Incident waves

D. Standing waves

12.

Micron is equal to _____ meter.

A. 10-10

B. 10-9

C. 10-6

D.

10-3

13. 1 Angstrom (A) is equal to _____.

A.

10-3

micronB. 10

-10 m

C.

10-6

micron

D. 10-6

m

14.

Why is it impossible to use waveguide at low radio frequencies?

A. Because of the size of the waveguide

B. Due to severe attenuation

C. Due to too much radiation

D.

All of these

15. _____ is the transmission and reception of information.

A. Modulation

B.

Communication

C.

Radiation

D. Emission

16. What is the loss of the circuit in dB if the power ratio of output to input is 0.01?

A. 20

B. -20

C. 40

D. -40


3/25

17.

Transmission lines either balanced or unbalanced with respect to

A. negative terminal

B. reference

C. ground

D.

positive terminal

18.

The standing wave ratio is equal to _____ if the load is properly matched with the transmission line.A. infinity

B.

0

C.

-1

D. 1

19.

_____ is the advantage of the balanced transmission line compared to unbalanced line.

A. Low attenuation

B. Easy installation

C. Low radiation loss

D.

Tensile strength

20. _____ is the method of determining the bandwidth of any processing system.

A.

Fourier series

B. Spectral analysis

C. Frequency analysis

D. Bandwidth analysis

21.

What causes the attenuation present in a waveguide?

A. The air dielectric filling the guide

B. The coating of silver inside

C. Losses in the conducting walls of the guide

D.

Radiation loss

22. A device that converts a balanced line to an unbalanced line of a transmission line.

A.

HybridB.

Stub

C.

Directional coupler

D. Balun

23.

What is the approximate line impedance of a parallel-strip line spaced 1 cm apart with the length of 50 cm?

A. 10 ohms

B. 15 ohms

C. 18 ohms

D.

23 ohms

24. What is the average power rating of RG-58 C/u?

A. 25 W

B.

50 W

C.

75 W

D. 200 W

25. A coaxial cable used for high temperatures.

A.

RG-58C

B. RG-11A

C. RG-213

D. RG-211A


4/25

26.

If you have available number of power amplifiers with a gain of 100 each, how many such amplifier do you

need to cascade to give an overall gain of 60 dB?

A. 2

B. 3

C.

4

D. 5

27. You are measuring noise in a voice channel at a -4 dB test point level, the meters reads -73 dBm, convert the

reading into dBrnCO.

A.

12

B. 16

C. 18

D. 21

28. The velocity factor of a transmission line

A. depends on the dielectric constant of the material used

B.

increase the velocity along the transmission line

C. is governed by the skin effect

D. is higher for a solid dielectric than for air

29. Impedance inversion by

A. a short-circuited stub

B. an open-circuited stub

C. a quarter-wave line

D.

a half-wave line

30. Transmission line when connected to antennas have

A. capacitive load

B.

resistive load whose resistance is greater than the characteristic impedance of the line

C. resistive load whose resistances is less than characteristic impedance of the line

D. resistive load at the resonant frequency

31.

One of the following is not a bounded media

A.

Coaxial line

B. Two-wire line

C. Waveguide

D. Ocean

32. The impedance measured at the input of the transmission line when its length is infinite.

A. Input impedance

B.

Open circuit impedance

C. Characteristic impedance

D. Short circuit impedance

33.

The following are considered primary line constants except

A.

conductance

B. resistance

C. capacitance

D. complex propagation constant


5/25

34.

The dielectric constants of materials commonly used in transmission lines range from about

A. 1.2 to 2.8

B. 2.8 to 3.5

C. 3.5 to 5.2

D.

1.0 to 1.2

35.

Typically, the velocity factor (Vr) of the materials used in transmission lines range fromA. 0.6 to 0.9

B.

0.1 to 0.5

C.

1.0 to 0.9

D. 0.6 to 0.8

36.

For an air dielectric two-wire line, the minimum characteristic impedance value is

A. 85 Ω

B. 83 Ω

C. 90 Ω

D.

88 Ω

37. When a quarter-wave section transmission line is terminated by a short-circuit and is connected to an RF

source at the other end, its input impedance is

A. inductive

B. capacitive

C. resistive

D. equivalent to a parallel resonant LC circuit

38. A transmitter operating at 30 MHz with 4 W output is connected via 10 m of RG-8A/u cable to an antenna that

has an input resistance of 300 Ω. Find the reflection coefficient.

A. 0.71

B.

0.77

C. 0.97

D. 0.76

39.

A quarterwave transformer is connected to parallel wire line in order to match the line load of 1000 Ω. The

transformers has a characteristic impedance of 316.23 Ω. The distance between centers is 4 inches. What is

the percentage reduction in the diameter of the line?

A. 85%

B. 83%

C. 86%

D. 90%

40.

The concept to make one Smith chart universal is called

A.

ionization

B. normalization

C. rationalization

D.

termination

41. What are the basic elements of communications systems?

A. Source, transmission channel, transmitter

B. Transmitter, receiver, transmission channel

C.

Information, transmission channel, receiver

D. Sender and receiver


6/25

42.

_____ is the transmission of printed material over telephone lines.

A. Internet

B. Data communications

C. Telegraphy

D. Facsimile

43.

_____ is continuous tone generated by the combination of the frequencies of 350 Hz 440 Hz used in telephonesets.

A.

DC tone

B.

Ringing tone

C. Dial tone

D. Call waiting tone

44. _____ are unidirectional amplifiers having 20-25 decibel gain that are placed about 75 km apart to

compensate for losses along the telephone line.

A. VF repeaters

B.

Loading coils

C. Loop extenders

D. Echo suppressors

45. _____ is a component in the telephone set that has primary function of interfacing the handset to the local

loop.

A. Resistor

B. Capacitor

C.

Varistor

D. Induction coil

46. Pulse dialling has _____ rate

A.

20 pulses/min

B. 10 pulses/min

C. 10 pulses/sec

D.

80 pulses/sec

47.

_____ is a telephone wire that connects two central offices.

A. 2-wire circuit

B. Trunk line

C.

Leased line

D. Private line

48. The central switching office coordinating element for all cell sites that has cellular processor cellular switch. It

interfaces with telephone company zone offices, control call processing and handle billing activities.

A. MTSO

B. Cell site

C. PTSN

D.

Trunk line

49. _____ in a cellular system performs radio-related functions for cellular site.

A. Switching system

B. Base station

C.

Operation and support system

D. Mobile station


7/25

50.

A technology used to increase the capacity of a mobile phone system.

A. Frequency re-use

B. Cell splitting

C. TDM

D.

FDM

51.

If the grade of service of a telephone system indicated P = 0.05, what does it mean?A. Completed calls of 5%

B. Lost calls of 5%

C.

Lost calls of 95%

D. Lost calls of 105%

52.

_____ is the Out-of-Band signalling between Toll Central Offices (Bell System Standard).

A. 3,825 Hz

B. 3700 Hz

C. 2,600 Hz

D.

800 Hz

53. In a telephone system, the customer’s telephone directory numbering is from 000 to 999, what is the capacity

of a telephone system numbering from 000 to 999?

A. 100 lines

B. 1000 lines

C. 10,000 lines

D. 100,000 lines

54. If the SWR is infinite, what type of load transmission line has?

A. Purely reactive

B. Purely resistive

C.

Purely capacitive

D. Purely inductive

55.

Not more that _____ digits make up an international telephone number as recommended by CCITT REC. E.161.

A.

8

B. 10

C. 11

D. 12

56. One (1) Erlang is equal to _____.

A. 360 CCS

B. 36 CCS

C.

3.6 CCS

D. 100 CCS

57.

Standard tariff for flat rate telephone service beyond the normal flat rate in that area.

A. WATS

B. OTLP

C. TIP

D. DTWX


8/25

58.

The standard analog telephone channel bandwidth.

A. 300-3400 Hz

B. 1200 Hz

C. 200-3200 Hz

D.

300-3000 Hz

59.

Type of switching in which a pair of wire from the telephone set terminates in a jack and the switch issupervised by an operator.

A.

Crossbar switching

B. Manual switching

C. Electronic switching

D. Step-by-step switching

60. Every time when the telephone is idle, the handset is in the _____ state.

A. on-hook

B. off-hook

C.

busy

D. spare

61.

_____ is component in the telephone set that has the primary function of compensating for the local loop

length.

A. Resistor

B. Varistor

C. Capacitor

D.

Induction coil

62. What kind of receiver is used in conventional telephone handset?

A. Carbon

B. Electromagnetic

C. Ceramic

D. Capacitor

63.

A voice-grade circuit using the PTN has an ideal passband of

A.

0 to 4 Hz

B. 0 to 4 MHz

C. 0. to 4 kHz

D.

0 to 4 GHz

64. _____ is the minimum-quality circuit available using the PTN.

A. Basic voice grade (VG)

B.

Basic voice channel (VC)

C.

Basic voice band (VB)

D. Basic telephone channel

65.

Direct distance dialling (DDD) network is called

A.

Private-line network

B. PT network

C. Dial-up network

D. Trunk network


9/25

66.

What is the advantage of sidetone?

A. Transmission efficiency is increases

B. Speaker increases his voice resulting in a strengthened signal

C. No dissipation of energy in balancing network

D. Assure the customer that the telephone is working

67.

_____ is a special service circuit connecting two private branch exchanges (PBX).A. Phantom line

B. Tie trunk

C.

Tandem trunk

D. Private line

68.

The published rates, regulations, and descriptions governing the provision of communications service for

public use.

A. Toll rate

B. Tariff

C.

Bulk billing

D. Detailed billing

69.

What is the power loss of a telephone hybrid?

A. 1 dB

B. 2 dB

C. 3 dB

D. 6 dB

70. Telephone channel has a band-pass characteristic occupying the frequency range of _____.

A. 300-400 Hz

B. 300-3400 Hz

C.

300-3000 Hz

D. 300-2700 Hz

71.

The first Strowger step-by-step switch used in _____.A.

1875

B.

1890

C. 1897

D. 1913

72. What is the phase delay of an 800 Hz voice signal if the phase shift is 15 degrees?

A. 52 μsec

B. 1.25 μsec

C.

83.33 μsec

D.

26 μsec

73. What is the CCITT recommendation for a preparation of loss plan, a variable loss plans and fixed loss plan?

A.

G.133

B.

G.141

C. G.132

D. G.122


10/25

74.

What is the diameter of a copper wire to be used in a 16 km loop with a dc loop resistance of 100 ohms/km?

A. 0.838 mm

B. 0.465 mm

C. 1.626 mm

D.

2.159 mm

75.

What kind of cell is appropriate for load management, fast moving mobiles and low-usage areas?A. Pico cells

B.

Micro cells

C.

Nano cells

D. Umbrella cells

76.

In cellular networks, standard base station antennas are replaced by _____.

A. adaptive array

B. flat plate antenna

C. dipole array

D.

focused antenna

77. What is the basis of the first generation wireless local loop?

A.

Digital cellular technology

B. Analog cellular technology

C. PSTN

D. AMPS technology

78.

When the calling party hears a “busy” tone on his telephone, the call is considered

A. lost

B. disconnected

C. complete

D.

incomplete

79. Short-circuited stubs are preferred to open circuited stubs because the latter are

A.

more difficult to make and connectB.

made of a transmission line with different characteristic impedance

C. liable to radiate

D. incapable of giving a full range of reactances

80.

What is the ratio of the reflected voltage to the incident voltage?

A. VSWR

B. ISWR

C. SWR

D. Coefficient of reflection

81. One method of determining antenna impedance.

A. Stub matching

B.

Trial and error

C.

Smith chart

D. Quarter-wave matching

82. _____ is a single conductor running from the transmitter to the antenna.

A. Single-wire line

B. Microstrip

C. Twin-lead

D. Coaxial line


11/25

83.

Coaxial cable impedance is typically _____.

A. 150 to 300 Ω

B. 50 to 75 Ω

C. 30 to 45 Ω

D.

300 to 600 Ω

84.

Waveguide becomes compulsory above what frequencies?A. Above 3 GHz

B.

Above 10 kHz

C.

At 300 MHz

D. Above 10 GHz

85.

Nominal voice channel bandwidth is _____.

A. 20 to 30 kHz

B. 0 to 3 kHz

C. 4 kHz

D.

55 kHz above

86. Echo suppressors are used on all communications systems when the round trip propagation time exceeds

_____.

A. 50 ms

B. 30 ms

C. 100 ms

D. 1 ms

87. A radio transmission line of Ω impedance is to be connected to an antenna having an input impedance of 150

Ω. What is the impedance of a quarter-wave matching line?

A. 212 Ω

B.

250 Ω

C. 200 Ω

D. 150 Ω

88.

Quarter-wavelength line is used as _____.

A. impedance transformer

B. lecher line

C. transmission line

D.

harmonic suppressor

89. The transmission lines which can convey electromagnetic waves only in higher modes is usually called

A. coaxial cable

B. waveguide

C.

power lines

D. twisted wire of telephone line

90.

Why is nitrogen gas sometimes used in waveguide?

A.

To increase the distributed capacitance

B. To keep the waveguide dry

C. To reduce the skin effect at the walls of the guide

D. To raise the guide’s wave impedance


12/25

91.

The apparent speed of propagation along a waveguide based on the distance between wavefronts along the

walls of the guide is called

A. group velocity

B. phase velocity

C.

normal velocity

D. abnormal velocity

92. How do you couple in and out of a waveguide?

A.

Wrap a coil of wire around one end of the waveguide

B.

Insertion of an E-probe into the waveguide

C. Insertion of a H-loop into the waveguide

D. Both B and C

93. A rectangular waveguide is operating in the dominant TE10 mode. The associated flux lines are established

A. transversely across the narrow dimension of the waveguide

B. transversely across the wide dimension of the waveguide

C.

in the metal walls parallel to the direction of propagation

D. in the metal walls perpendicular to the direction of propagation

94.

For the dominant mode of a rectangular waveguide, the distance between two instantaneous consecutive

positions of maximum field intensity (in a direction parallel to the walls of the waveguide) is referred to as half

of the

A. free-space wavelength

B. cutoff wavelength in the wide dimension

C. guide wavelength

D. group wavelength

95. The guide wavelength, λg, in a rectangular waveguide is

A.

equal to the free-space wavelength at the cut-off frequency

B. equal to the free-space wavelength for the same signal frequency

C. less than the free-space wavelength at the cut-off frequency

D.

greater than the free-space wavelength at the same signal frequency

96.

Using the TE10 mode, microwave power can only be transmitted in free rectangular guide provided

A. the wider dimension is less than one-half of the wavelength in free space

B. the narrow dimension is less than one-quarter of the wavelength in free-space

C.

the wide dimension is greater than on-half of the guide wavelength

D. the wide dimension is greater than one-half of the wavelength in free-space

97. If the signal frequency applied to a rectangular guide is increase and the dominant mode is employed

A.

the free-space wavelength, λ, is increased

B.

the phase velocity, Vψ, is increased

C. the guide wavelength is increased

D. the group velocity, Vg, is increased


13/25

98.

If a 6 GHz signal is applied to a rectangular waveguide and the reflection angle, θ, is 20o, what is the value of

the guide wavelength, λg?

A. 6.10 cm

B. 5.32 cm

C.

4.78

D. 5.00 cm

99. The inner dimensions of a rectangular waveguide are 1.75 cm by 3.5 cm. the cutoff wavelength for the

dominant mode is

A.

1.75 cm

B. 3.5 cm

C. 7.0 cm

D.

0.4375 cm

100. A signal whose wavelength is 3.5 cm is being propagated along a guide whose inner dimensions are 2 cm by 4

cm. What is the value of the guide wavelength, λg ?

A.

3.12 cm

B. 3.89 cm

C. 3.57 cm

D.

6.30 cm

101. The frequency range ever which a rectangular waveguide is excited in the domain mode is limited to

A. the difference between the frequency for which the reflection angle, θ, is 90o and the frequency for

which θ is zero.

B.

the difference between the frequency for which the free-space wavelength is equal to the cutoff value

and the frequency for which the free-space wavelength id equal to the guide wavelength

C. the difference between the frequency at which the cutoff wavelength is twice the narrow dimension

D. None of these

102. If a rectangular waveguide is to be excited in the dominant mode, the E -probe should be inserted

A. at the sealed end

B.

at a distance of one quarter-wavelength from the sealed end C.

at a distance of one-half wavelength from the sealed end

D.

at a distance of three-quarters of a wavelength from the sealed end

103. A quarter-wave line is connected to an RF generator and is shorted out at the far end. What is the input

impedance to the line generator?

A. A low value of resistance

B. A high value of resistance

C. A capacitive resistance which is equal in the value to the line’s surge impedance

D.

An inductive resistance which is equal to the value to the line’s surge impedance

104. If the SWR on a transmission line has a high value, the reason could be

A. an impedance mismatch between the line and the load

B.

that the line is non-resonant

C. a reflection coefficient of zero at the load

D. that the load is matched to the line


14/25

105.

If a quarter-wave transmission line is shorted at one end

A. there is minimum current at the shorted end

B. the lie behaves as a parallel-tuned circuit in relation to the generator

C. the line behaves as a series-tuned circuit in relation to the generator

D.

there is a minimum voltage at the shorted end

106.

A 50-ohm transmission line is feeding an antenna which represents a 50 Ω resistive load. To shorten the line,the length must be

A. any convenient value

B.

an odd multiple of three-quarters of a wavelength

C. an odd multiple of half a wavelength

D. an even multiple of a quarter of a wavelength

107. The outer conductor of the coaxial cable is usually grounded

A. at the beginning and at the end of the cable

B. only at the beginning of the cable and only at the end of the cable

C.

only at the end of the cable

D. at the middle of the cable

108.

A feature of an infinite transmission line is that

A. its input impedance at the generator is equal to the line’s surge impedance

B. its phase velocity is greater than the velocity of light

C. no RF current will be drawn from the generator

D. the impedance varies at different positions on the line

109. When the surge impedance of a line is matched to the load, the line will

A. transfer maximum current to the load

B. transfer maximum voltage to the load

C. transfer maximum power to the load

D. have a VSWR equal to zero

110.

A lossless line is terminated by a resistive load which is not equal to the surge impedance. If the value of thereflection coefficient is 0.5, the VSWR is

A.

2

B. 3

C. 4

D.

15

111. Ratio of the mismatch between the antenna and the transmitter power.

A.

Standing wave pattern

B. Reflection coefficient

C. SWR

D. index of refraction


15/25

112.

Emission designation for a facsimile.

A. H3E and A4E

B. R3E and A4E

C. F4E and J3E

D. F3C and A3E

113.

Commonly used telephone wire. A. AWG #19

B. AWG #18

C. AWG #30

D. AWG #33

114. What is the distance travelled by a wave in the time of one cycle?

A. Frequency

B.

Hop

C. Wavelength

D. Crest

115.

The velocity factor is inversely proportional with respect to the _____.

A.

square of the dielectric constant

B. square root of the dielectric constant

C. dielectric constant

D. square root of refractive index

116. _____ is a hollow structure that has no center conductor but allows waves to propagate down its length.

A. Waveguide

B.

Hybrid

C.

Pipe

D. Directional coupler

117.

To connect a coaxial line to a parallel wire line, _____ is used.A.

hybrid circuit

B. balun

C. directional coupler

D. quarter-wave transformer matching circuit

118. What length for which the input power has been halved for a transmission line with an attenuation of 6

dB/km?

A.

1.5 km

B. 0.5 km

C. 63 km

D. 2 km

119.

In a waveguide, _____ is a specific configuration of electric and magnetic fields that allows a wave to

propagate.

A. set-up

B. coupler

C.

channel

D. mode


16/25

120.

A rectangular waveguide has dimensions of 3 cm x 5 cm. What is the dominant mode cut-off frequency?

A. 2 GHz

B. 3 GHz

C. 2.5 GHz

D.

3.5 GHz

121.

_____ are transmission lines which can convey electromagnetic waves only in higher order modes?A. Coaxial cables

B.

Twisted pairs of telephone wire

C.

Power cables

D. Waveguides

122.

The amount of uncertainty in a system of symbols is also called

A. bandwidth

B. loss

C. entropy

D.

quantum

123. The twists in twisted wire pairs

A.

reduced electromagnetic interference

B. occur at a 30-degree angle

C. eliminate loading

D. were removed due to cost

124.

An example of a bounded medium is

A. coaxial cable

B. waveguide

C. fiber-optic cable

D. all of the above

125. Loading means the addition of

A.

resistorB.

capacitor

C.

bullet

D. inductance

126.

What is the most commonly used transmission line for high frequency application?

A. Two-wire balance line

B. Single wire

C. Three-wire line

D. Coaxial

127. The characteristic impedance of a transmission line does not depend upon its

A. length

B.

conductor diameter

C.

conductor spacing

D. dielectric material

128. One of the following is not a common transmission line impedance.

A.

50 Ω

B. 75 Ω

C. 120 Ω

D. 300 Ω


17/25

129.

For maximum absorption of power at the antenna, the relationship between the characteristic impedance of

the line Zo and the load impedance ZL should be

A. Zo = ZL

B. Zo > ZL

C.

Zo < ZL

D. Zo = 0

130.

The mismatch between antenna and transmission line impedance cannot be corrected for by

A. using LC matching network

B. adjusting antenna length

C. using a balun

D. adjusting the length of transmission line

131. _____ is a pattern of voltage and current variations along a transmission line not terminated in its

characteristic impedance.

A.

an electric field

B. radio waves

C. standing waves

D. a magnetic field

132.

Which is the desirable SWR on a transmission line?

A. 0

B. 1

C. 2

D. infinity

133. A 50 Ω coax is connected to a 73 Ω antenna. What is the SWR?

A.

0.685

B.

1

C. 1.46

D. 2.92

134.

What is the most desirable reflection coefficient?

A. 0

B. 0.5

C. 1

D. infinity

135. What is the ratio expressing the percentage of incident voltage reflected on a transmission line?

A.

Velocity factor

B. Standing-wave ratio

C. Reflection coefficient

D. Line efficiency

136.

The minimum voltage along a transmission line is 260 V, while the maximum is 390 V the SWR is

A. 0.67

B. 1.0

C. 1.2

D. 1.5


18/25

137.

One meter is one wavelength at a frequency of

A. 150 MHz

B. 164 MHz

C. 300 MHz

D.

328 MHz

138.

At very high frequencies, transmission line act asA. tuned circuits

B. antennas

C.

insulators

D. resistors

139.

A shorted quarter-wave line at the operating frequency acts like a/an

A. capacitor

B. inductor

C. series resonant circuit

D. parallel resonant circuit

140. A shorted half-wave line at the operating frequency acts like a/an

A.

capacitor

B. inductor

C. series resonant circuit

D. parallel resonant circuit

141.

A medium least susceptible to noise

A. Shielded pair

B. Twisted pair

C. Fiber-optic

D. Coaxial

142. A medium most widely used in LANs?

A.

Parallel-wire lineB.

Twisted pair

C.

Fiber-optic cable

D. Coaxial

143.

The most commonly used transmission line in television system.

A. Parallel-wire line

B. Coaxial cable

C. Waveguide

D.

Open-wire with ceramic supports

144. The impedance of a TV transmission line depends on several factors. Which is not one of those factors?

A. Diameter

B.

Length of the wire

C.

Dielectric material

D. Separation between conductors

145. DC blocks are used in coaxial transmission line for the purpose of

A.

passing DC while blocking AC

B. passing AC voltage but prevent DC

C. preventing AC voltage from reaching the pre-amplifier

D. preventing AC power supply voltage from being shorted by a balun or band splitter


19/25

146.

_____ is a type of interference caused by off-air TV channels 2 and 4, plus a satellite dish operating on channel

3.

A. Adjacent channel interference

B. Ghost

C.

Co-channel interference

D. Crosstalk

147. Dithering (in TVRO communications) is a process for

A. reducing the effect of noise on the TVRO video signal

B.

centering the video fine tuning on TVRO channels

C. moving the feedhorn rotor to the precise angle

D. moving the actuator exactly onto the desired satellite beam

148. A network that has an input of 75 dB and an output of 35 dB. The loss of the network is _____.

A. -40 dB

B. 40 dB

C.

40 dBm

D. -40 dBm

149.

Important useful quantities describing waveforms.

A. Time and frequency

B. Voltage and current

C. Frequency and voltage

D. Power and frequency

150. Halving the power means

A. 6-dB gain

B. 3-dB loss

C.

3-dB gain

D. 6-dB loss

151.

One neper (Np) is how many decibelsA.

8.866

B. 8.686

C. 8.688

D. 8.868

152. A signal is amplified 100 times in power. The dB gain is

A. 20 dB

B. 119 dB

C.

15 dB

D.

25 dB

153. Which of the following is used to measure SWR?

A.

Spectrum analyzer

B. Reflectometer

C. Oscilloscpoe

D. Multimeter


20/25

154.

214-056 twin lead which is commonly used for TV lead-in has a characteristic impedance of

A. 52 Ω

B. 75 Ω

C. 600 Ω

D. 300 Ω

155.

What is the characteristic impedance of a transmission line which is to act as a quarterwave matchingtransformer between a 175 Ω transmission line and 600 Ω load?

A.

300.04 Ω

B. 324.04 Ω

C. 310.04 Ω

D. 320.04 Ω

156. What is the EIRP in dBW of a 50 dB antenna connected to transmitter with an output of 10 kW through a

transmission line with a loss of 5 dB?

A. 85 dBW

B.

955 dBW

C. 90 dBW

D. 80 dBW

157. A coaxial cable is a god example of a/an

A. unbounded medium

B. transmission channel

C. non-metallic medium

D. bounded medium

158. If a quarterwave transformer is required to match a 180 Ω load to a transmission line with an impedance of

300 Ω, what should be the characteristic impedance of the matching transformer is to be connected directly to

the load.

A. 180 Ω

B. 232 Ω

C.

300 Ω D.

480 Ω

159. A transmitter of 100 W RF power output, 100% modulated is operating on a frequency of 169 MHz. The

antenna transmission line consists of a 50 Ω coaxial cable, 150 ft long. The coaxial inner conductor outer

diameter is 0.162 in. Determine the outside diameter of the outer conductor if the outer conductor has a

thickness of 0.05 in (Assume k = 1).

A. 1.0 in

B. 0.9 in

C.

0.7 in

D. 0.5 in

160. In the preceding problem, calculate the line current.

A.

1.7 A

B.

1.3 A

C. 1.5 A

D. 1.0 A


21/25

161.

Determine also the attenuation of the line in the preceding problem.

A. 2.0 dB

B. 1.5 dB

C. 2.5 dB

D.

1.0 dB

162.

What is the maximum subscriber loop length, in ft , of a telephone system if the signalling resistance is 1800 Ωusing a telephone cable pair of gauge # 26 with a loop resistance if 83.5 Ω per 100 ft. Assume the telephone

set resistance is equal to 200 Ω.

A.

15,161.7 ft

B. 19,161 ft

C. 15,300 ft

D.

20,000 ft

163. If the same subscriber loop above limits the voice attenuation to a maximum of 6 dB, what is the maximum

allowable subscriber loop length, in ft, using the same gauge # 26 telephone wire? Assume a 2.7 dB loss per

mile.

A. 20,000 ft

B. 13,900 ft

C.

15,280 ft

D. 11,733 ft

164. The input is 0.1 W and the network gain is 13 dB, the output is

A. 2.0 W

B.

2.5 W

C. 1.5 W

D. 1.8 W

165.

Known as one-tenth of neper

A. dB

B. dBm

C.

dBpD. dNp

166. The input impedance of a quarterwave short-circuited transmission line at its resonant frequency is

A. 0 Ω

B. infinite or open circuit

C. Ω

D. 70 Ω

167.

The ratio of the largest rms value to the smallest rms value of the voltage in the line is called

A.

SWR

B. ISWR

C. VSWR

D.

Coefficient of reflection

168. An open-wire, two-wire transmission line is to be connected to a dipole antenna through a quarter-wave

matching stub. At a frequency of 10 MHz, compute the length of the dipole.

A. 20 m

B.

7.5 m

C. 15 m

D. 25 m


22/25

169.

From the preceding problem, compute also the length of the quarterwave stub

A. 15 m

B. 7.5 m

C. 20 m

D.

25 m

170.

To find the characteristic impedance of a coaxial cable, measurements are made with (a) the far end opencircuited and (b) far end short circuited, the corresponding readings being

a)

Ro = 3 Ω and Xc = 55 Ω, capacitive

b)

Rs = 10 Ω and XL = 90 Ω, inductive

What is the characteristic impedance, Zo, of the line?

A. 75.7 – j2.0 Ω

B.

70.7 + j1.19 Ω

C. 87.5 – j5 Ω

D. 70.7 – j1.97 Ω

171.

A TV antenna receives a signal measured at 200 mV and is immediately amplified by a pre-amplifier with a 15

dB gain. This amplified signal then passes through a coaxial cable with 3 dB loss, what is the resulting input to

the TV set, in dBmV?

A.

1.98

B. 13.98

C. -1.98

D. -13.98

172.

The characteristic impedance line does not depend upon its _____.

A. conductor spacing

B. conductor diameter

C. length

D.

conductor radius

173. What does a power difference of -3 dB mean?

A.

What does a power difference of -3 dB mean?B.

a loss of one half of the power

C.

a loss of three watts of power

D. no significant change

174.

Which of the following is an advantage of the balance transmission line?

A. Easy installation

B. Outer shield eliminates radiation losses

C. Low attenuation

D.

None of these

175. Waveguides are used mainly for microwave transmission because

A. they are bulky at lower frequencies

B.

losses are heavy at lower frequencies

C.

they depend on straight line propagation

D. no generators are powerful enough to excite them

176. The input is 1 W and the network loss is 27 dB, the output is

A.

1 mW

B. 3 mW

C. 2 mW

D. 4 mW


23/25

177.

A combiner has two inputs + 30 dBm and + 30 dBm, what is the resultant output?

A. + 36 dBm

B. + 30 dBm

C. + 60 dBm

D. + 33 dBm

178.

The ratio of the smallest to the largest rms current value is calledA. SWR

B.

VSWR

C. ISWR

D. Coefficient of reflection

179.

If the ratio of the maximum current to minimum current in a transmission line is 2:1 then the ratio of

maximum voltage to minimum voltage is

A. 4:1

B. 1:2

C.

1:4

D. 2:1

180.

Two wires of 600 Ω characteristics impedance is to be constructed out of a number 12 wire (81 mils). Find the

attenuation of the line at 0.6 GHz per 100 feet length.

A. 0.05 dB

B. 0.55 dB

C. 0.44 dB

D.

0.35 dB

181. In the preceding problem, determine the spacing between wires from center to center.

A. 6 in

B.

4 in

C. 5 in

D. 3 in

182.

A lossless transmission line has a shunt capacitance of 100 nF/m and a series inductance of 4 mH/m. What is

the characteristic impedance?

A. 500 Ω

B. 400 Ω

C.

300 Ω

D. 200 Ω

183. A ten times power change in transmission system is equivalent to

A.

10 dBm

B. 10 dB

C. 20 dB

D. 100 dB

184.

A type of transmission line employed where balanced properties are required

A. Balun

B. Parallel-wire line

C. Coaxial line

D.

Quarterwave line


24/25

185.

What is the characteristic impedance of a transmission line has a capacitance of 40 nF/ft and an inductance of

0.5mH/ft

A. 111.8 Ω

B. 110.8 Ω

C.

112.8 Ω

D. 109.8 Ω

186. The input power to a loss-free cable is 5 W. If the reflected power is 7 dB down on the incident power, the

output power to the load is

A. 4 W

B. 5 W

C. 6 W

D.

7 W

187. To be properly matched the ratio of a maximum voltage along a transmission line should be equal to

A. 1

B.

10

C. 50

D. 2

188. A coaxial line with an outer diameter of 6 mm has a 50 Ω characteristic impedance. If the dielectric constant of

the insulation is 1.60, calculate the inner diameter.

A. 2.09 cm

B. 2.09 in

C. 2.09 mm

D. 2.09 mm

189. If an amplifier has equal input and output impedances, what voltage ratio does the gain of 50 dB represent?

A. 316.2

B. 325.2

C. 320.1

D.

315.0

190.

What is the inductance per foot of a cable that has a capacitance of 50 pF/ft and a characteristic impedance of

60 Ω?

A. 0.167 μH/ft

B.

0.178 μH/ft

C. 0.19 μH/ft

D. 0.18 μH/ft

191.

The ratio between the energy absorbed by a surface to the total energy received by the surface.

A.

Reflection coefficient

B. Absorption coefficient

C. Linear coefficient

D.

Thermal coefficient

192. When the diameter of the conductors of a 2 wire transmission line is held constant, the effect of decreasing

the distance between the conductors is

A. increase the surge impedance

B.

increase the radiation resistance

C. decrease the SWR

D. decrease the impedance


25/25

193.

The higher the gauge number of a conductor

A. the bigger the diameter

B. the higher the resistance or the smaller the diameter

C. the higher the resistance

D.

none of these

194.

A short length of transmission line used to reduce/eliminate standing waves in the main transmission line.A. Stub

B.

Balun

C. λ/4 transformer

D. Slot

195.

Ratio of reflected power to incident power?

A. Incidence

B. Reflectance

C. Reflection index

D.

None of these

196. A quarter wave transformer is used to match a 600 Ω load antenna to a line of 52 Ω impedance, the

characteristic impedance of the matching transformer is

A. 200 Ω

B. 150 Ω

C. 176 Ω

D. 300 Ω

197. What is the capacitance of 55 miles #44 copper wire spaced 18 inches? From wire tables, #44 wire has a radius

to 0.10215 in.

A. 0.476 μF

B.

0.476 nF

C. 0.476 pF

D. 0.476 fF

198.

A two-wire transmission line consists of No. 12 wire AWG (81 mils). The distance between wire centers is 10

inches. What is the characteristic impedance of the line?

A. 650 Ω

B. 300 Ω

C.

600 Ω

D. 660 Ω

199. In the preceding problem, what is the attenuation in dB per 100 ft. of the line for a frequency of 4 MHz?

A.

0.05

B. 0.03

C. 0.04

D. 0.06

200.

What is the SWR when a transmission line is terminated in a short circuit?

A. Zero

B. One

C. Infinite

D.

Indeterminate

Documents

CHAPTER 1 Transmission Fundamentals