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TRANSMISSION LINES > 300 QUESTION BOARD EXAM REVIEWER PART2 > Flashcards

300 QUESTION BOARD EXAM REVIEWER PART2 Flashcards

1
Q
  1. If the SWR is infinite, what type of load does the transmission line has?
A

Purely reactive

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2
Q
  1. The standard analog telephone channel bandwidth.
A

300 – 3400 Hz

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3
Q
  1. Telephone channel has a band-pass characteristic occupying the frequency range of?
A

300 – 3400Hz

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4
Q
  1. Short Circuit Stubs are preferred to open circuit stubs because the latter are?
A

Liable to radiate

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5
Q
  1. What is the ratio of the reflected voltage to the incident voltage?
A

Reflected voltage

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6
Q
  1. One method of determining antenna impedance?
A

Quarter wave matching

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7
Q
  1. Coaxial cable impedance is typically _____.
A

50-75 ohms

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8
Q
  1. Waveguides become compulsory above what frequencies?
A

Above 3 GHz

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9
Q
  1. Nominal voice channel bandwidth is _____.
A

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

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10
Q
  1. Quarter-wavelength line is used as _____.
A

Impedance transformer

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11
Q
  1. The transmission lines which can convey electromagnetic waves only in higher modes is usually called _____.
A

Waveguide

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12
Q
  1. Why is nitrogen gas sometimes used in waveguide?
A

To keep the waveguide dry

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13
Q
  1. The apparent speed of propagation along a waveguide based on the distance between wavefronts along the walls of the guide is called?
A

Phase velocity

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14
Q

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 high value of resistance

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15
Q

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

A

An impedance mismatch between line and load

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16
Q

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

A

The line behaves as a parallel-tuned circuit.

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17
Q

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

A

Any convenient value

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18
Q

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

A

The beginning and the end of the cable.

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19
Q

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

A

equal to

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20
Q

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

A

Transfer maximum power to the load

21
Q

Other terminology for Characteristic Impedance

A

Surge Impedance

22
Q

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?

A

3

23
Q

Ratio of the mismatch between the antenna and the transmitter?

A

SWR

24
Q

Commonly used telephone wire?

A

AWG #19

25
Q

Distance travelled by a wave in one cycle?

A

Wavelength

26
Q

The velocity factor is inversely proportional with respect to the?

A

square root of the dielectric constant

27
Q

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

A

Waveguide

28
Q

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

A

Balun (coaxial is unbalanced, parallel is balanced)

29
Q

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

A

Mode

30
Q

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

A

Waveguide

31
Q

The twists in twisted wire pairs do what?

A

It reduces electromagnetic interference

32
Q

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

A

Coaxial

32
Q

Loading means the addition of?

A

Inductance

33
Q

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

A

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

34
Q

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

A

120

35
Q

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

A

Equal

36
Q

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

A

Standing Waves

37
Q

What is the desirable SWR on a transmission line?

A

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

38
Q

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

A

1.46 (73-50/73+50 —- 1+x / 1-x)

39
Q

What is the most desirable reflection coefficient?

A

0 (no reflection, all absorbed)

40
Q

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

A

Reflection Coefficient

41
Q

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

A

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

42
Q

At very high frequencies, transmission lines act as?

A

Antennas

42
Q

One meter is one wavelength at a frequency of?

A

300MHz (Speed of Light / Frequency = Wavelength)

43
Q

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

A

Parallel resonant circuit

44
Q

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

A

Series resonant circuit

45
Q

A medium least susceptible to noise?

A

Coaxial

46
Q

A medium most widely used in LANs?

A

Twisted Pairs

TRANSMISSION LINES (5 decks)

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