Chapter 2, Antennas Flashcards

1
Q

An isotropic radiator will radiate

A

Uniformly in all directions

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2
Q

Another name for a quarter-wave vertical
antenna is

A

A Marconi antenna

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3
Q

A full-wave dipole fed at the center must be

A

Current fed

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4
Q

The radiation efficiency of an antenna

A

Decreases with antenna loss resistance

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5
Q

A vertical quarter-wave antenna will have a polar diagram in the horizontal plane which is

A

Omnidirectional

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6
Q

Which one of the following gives the
approximate length of a half-wave dipole for use at 300 MHz?

A

50 cm

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7
Q

A standing wave ratio of 1:1 indicates

A

That there will be no reflected power

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8
Q

Which one of the following antenna types
would be most suitable for a fixed long
distance HF communications link?

A

A three-element horizontal Yagi

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9
Q

When two antennas are vertically stacked the combination will have

A

Increased gain and unchanged beamwidth

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10
Q

The characteristic impedance of a coaxial
cable depends on

A

The ratio of inductance to capacitance

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11
Q

The attenuation of an RF signal in a coaxial cable

A

Increases with frequency

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12
Q

If a transmission line is perfectly matched to an aerial load it will

A

It appears to be infinitely long

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13
Q

The characteristic impedance of an RF coaxial cable is

A

Usually between 50 and 75 Ω

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14
Q

The beamwidth of an antenna is measured

A

Between the 70% power points

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