E9B01

What determines the free-space polarization of an antenna?

  1. The orientation of its electric field (E Field)

E9B02

In the antenna radiation pattern shown in Figure E9-1, what is the 3-dB beamwidth?

  1. 50 degrees

E9B03

In the antenna radiation pattern shown in Figure E9-1, what is the front-to-back ratio?

  1. 18 dB

E9B04

In the antenna radiation pattern shown in Figure E9-1, what is the front-to-side ratio?

  1. 14 dB

E9B05

What may occur when a directional antenna is operated at different frequencies within the band for which it was designed?

  1. The gain may exhibit significant variations

E9B06

What usually occurs if a Yagi antenna is designed solely for maximum forward gain?

  1. The front-to-back ratio decreases

E9B07

If the boom of a Yagi antenna is lengthened and the elements are properly retuned, what usually occurs?

  1. The gain increases

E9B08

How does the total amount of radiation emitted by a directional (gain) antenna compare with the total amount of radiation emitted from an isotropic antenna, assuming each is driven by the same amount of power?

  1. There is no difference between the two antennas

E9B09

How can the approximate beamwidth of a directional antenna be determined?

  1. Note the two points where the signal strength of the antenna is 3 dB less than maximum and compute the angular difference

E9B10

What type of computer program technique is commonly used for modeling antennas?

  1. Method of Moments

E9B11

What is the principle of a Method of Moments analysis?

  1. A wire is modeled as a series of segments, each having a distinct value of current

E9B12

What is a disadvantage of decreasing the number of wire segments in an antenna model below the guideline of 10 segments per half-wavelength?

  1. The computed feed-point impedance may be incorrect

E9B13

Which of the following is a disadvantage of NEC-based antenna modeling programs?

  1. Computing time increases as the number of wire segments is increased

E9B14

What does the abbreviation NEC stand for when applied to antenna modeling programs?

  1. Numerical Electromagnetics Code

E9B15

What type of information can be obtained by submitting the details of a proposed new antenna to a modeling program?

  1. A. SWR vs. frequency charts
  2. B. Polar plots of the far-field elevation and azimuth patterns
  3. C. Antenna gain
  4. D. All of these answers are correct

 

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