300 QUESTION BOARD EXAM REVIEWER PART2

Question 1

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

Answer 1

Purely reactive

Question 2

58. The standard analog telephone channel bandwidth.

Answer 2

300 – 3400 Hz

Question 3

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

Answer 3

300 – 3400Hz

Question 4

79. Short Circuit Stubs are preferred to open circuit stubs because the latter are?

Answer 4

Liable to radiate

Question 5

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

Answer 5

Reflected voltage

Question 6

81. One method of determining antenna impedance?

Answer 6

Quarter wave matching

Question 7

83. Coaxial cable impedance is typically _____.

Answer 7

50-75 ohms

Question 8

84. Waveguides become compulsory above what frequencies?

Answer 8

Above 3 GHz

Question 9

85. Nominal voice channel bandwidth is _____.

Answer 9

4kHz (Nominal is like in name only, actual is 300-3700Hz)

Question 10

88. Quarter-wavelength line is used as _____.

Answer 10

Impedance transformer

Question 11

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

Answer 11

Waveguide

Question 12

90. Why is nitrogen gas sometimes used in waveguide?

Answer 12

To keep the waveguide dry

Question 13

91. The apparent speed of propagation along a waveguide based on the distance between wavefronts along the walls of the guide is called?

Answer 13

Phase velocity

Question 14

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?

Answer 14

A high value of resistance

Question 15

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

Answer 15

An impedance mismatch between line and load

Question 16

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

Answer 16

The line behaves as a parallel-tuned circuit.

Question 17

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

Answer 17

Any convenient value

Question 18

The outer conductor of the coaxial cable is usually grounded at?

Answer 18

The beginning and the end of the cable.

Question 19

A feature of an infinite transmission line is that? Its input impedance at the generator is _____ line’s surge impedance

Answer 19

equal to

Question 20

When the Surge impedance of a line is matched to a load, the line will?

Answer 20

Transfer maximum power to the load

Question 21

Other terminology for Characteristic Impedance

Answer 21

Surge Impedance

Question 22

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

Answer 22

3

Question 23

Ratio of the mismatch between the antenna and the transmitter?

Answer 23

SWR

Question 24

Commonly used telephone wire?

Answer 24

AWG #19

Question 25

Distance travelled by a wave in one cycle?

Answer 25

Wavelength

Question 26

The velocity factor is inversely proportional with respect to the?

Answer 26

square root of the dielectric constant

Question 27

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

Answer 27

Waveguide

Question 28

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

Answer 28

Balun (coaxial is unbalanced, parallel is balanced)

Question 29

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

Answer 29

Mode

Question 30

_____ are transmission lines which can convey electromagnetic waves in higher order modes

Answer 30

Waveguide

Question 31

The twists in twisted wire pairs do what?

Answer 31

It reduces electromagnetic interference

Question 32

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

Answer 32

Coaxial

Question 32

Loading means the addition of?

Answer 32

Inductance

Question 33

The characteristics of a transmission line does not depend on what? length, conductor diameter, conductor spacing, dielectric material.

Answer 33

Length (Very important, know that Surge Impedance is not affected by length)

Question 34

One of the following is not a common transmission line impedance: 50, 75, 120, 300.

Answer 34

120

Question 35

For maximum absorption of power at the antenna, the relationship between Zo and Zl should be?

Answer 35

Equal

Question 36

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

Answer 36

Standing Waves

Question 37

What is the desirable SWR on a transmission line?

Answer 37

1 (SWR is from1 to infinity. 1SWR means 0 reflection coefficient, meaning: max power transfer)

Question 38

A 50 ohm Coax is connected to a 73 ohm antenna. What's the SWR?

Answer 38

1.46 (73-50/73+50 ---- 1+x / 1-x)

Question 39

What is the most desirable reflection coefficient?

Answer 39

0 (no reflection, all absorbed)

Question 40

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

Answer 40

Reflection Coefficient

Question 41

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

Answer 41

1.5 = [1 + (390-260/390+260) / 1 - (390-260/390+260)]

Question 42

At very high frequencies, transmission lines act as?

Answer 42

Antennas

Question 42

One meter is one wavelength at a frequency of?

Answer 42

300MHz (Speed of Light / Frequency = Wavelength)

Question 43

A shorted quarter-wave line at the operating frequency acts like?

Answer 43

Parallel resonant circuit

Question 44

A shorted half-wave line at the operating frequency acts like?

Answer 44

Series resonant circuit

Question 45

A medium least susceptible to noise?

Answer 45

Coaxial

Question 46

A medium most widely used in LANs?

Answer 46

Twisted Pairs