Antenna patterns: E and H plane patterns; gain as a function of pattern; antenna design; Yagi antennas

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E9B-2012: Antenna patterns: E and H plane patterns; gain as a function of pattern; antenna design; Yagi antennas

E9B01-2012:
In the antenna radiation pattern shown in Figure E9-1, what is the 3-dB beamwidth?

50 degrees

75 degrees

25 degrees

30 degrees

E9B02-2012:
In the antenna radiation pattern shown in Figure E9-1, what is the front-to-back ratio?

18 dB

36 dB

24 dB

14 dB

E9B03-2012:
In the antenna radiation pattern shown in Figure E9-1, what is the front-to-side ratio?

14 dB

12 dB

18 dB

24 dB

E9B04-2012:
What may occur when a directional antenna is operated at different frequencies within the band for which it was designed?

The gain may change depending on frequency

Feed point impedance may become negative

The E-field and H-field patterns may reverse

Element spacing limits could be exceeded

E9B05-2012:
What usually occurs if a Yagi antenna is designed solely for maximum forward gain?

The front-to-back ratio decreases

The front-to-back ratio increases

The frequency response is widened over the whole frequency band

The SWR is reduced

E9B06-2012:
If the boom of a Yagi antenna is lengthened and the elements are properly retuned, what usually occurs?

The gain increases

The SWR decreases

The front-to-back ratio increases

The gain bandwidth decreases rapidly

E9B07-2012:
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?

They are the same

The total amount of radiation from the directional antenna is increased by the gain of the antenna

The total amount of radiation from the directional antenna is stronger by its front to back ratio

The radiation from the isotropic antenna is 2.15 dB stronger than that from the directional antenna

E9B08-2012:
How can the approximate beamwidth in a given plane of a directional antenna be determined?

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

Measure the ratio of the signal strengths of the radiated power lobes from the front and rear of the antenna

Draw two imaginary lines through the ends of the elements and measure the angle between the lines

Measure the ratio of the signal strengths of the radiated power lobes from the front and side of the antenna

E9B09-2012:
What type of computer program technique is commonly used for modeling antennas?

Method of Moments

Graphical analysis

Mutual impedance analysis

Calculus differentiation with respect to physical properties

E9B10-2012:
What is the principle of a Method of Moments analysis?

A wire is modeled as a series of segments, each having a uniform value of current

A wire is modeled as a single sine-wave current generator

A wire is modeled as a series of points, each having a distinct location in space

A wire is modeled as a series of segments, each having a distinct value of voltage across it

E9B11-2012:
What is a disadvantage of decreasing the number of wire segments in an antenna model below the guideline of 10 segments per half-wavelength?

The computed feed point impedance may be incorrect

Ground conductivity will not be accurately modeled

The resulting design will favor radiation of harmonic energy

The antenna will become mechanically unstable

E9B12-2012:
What is the far-field of an antenna?

The region where the shape of the antenna pattern is independent of distance

The region of the ionosphere where radiated power is not refracted

The region where radiated power dissipates over a specified time period

The region where radiated field strengths are obstructed by objects of reflection

E9B13-2012:
What does the abbreviation NEC stand for when applied to antenna modeling programs?

Numerical Electromagnetics Code

Next Element Comparison

National Electrical Code

Numeric Electrical Computation

E9B14-2012:
What type of information can be obtained by submitting the details of a proposed new antenna to a modeling program?

All of these choices are correct

SWR vs. frequency charts

Polar plots of the far-field elevation and azimuth patterns