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

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

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

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

- Feed point impedance may become negative
- The E-field and H-field patterns may reverse
- Element spacing limits could be exceeded
- The gain may change depending on frequency

What type of antenna pattern over real ground is shown in Figure E9-2?

What is the elevation angle of peak response in the antenna radiation pattern shown in Figure E9-2?

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?

- 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
- They are the same
- The radiation from the isotropic antenna is 2.15 dB stronger than that from the directional antenna

How can the approximate beam-width 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

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

- Graphical analysis
- Method of Moments
- Mutual impedance analysis
- Calculus differentiation with respect to physical properties

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

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

- Ground conductivity will not be accurately modeled
- The resulting design will favor radiation of harmonic energy
- The computed feed point impedance may be incorrect
- The antenna will become mechanically unstable

What is the far field of an antenna?

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

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

- Next Element Comparison
- Numerical Electromagnetic Code
- National Electrical Code
- Numeric Electrical Computation

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

- SWR vs frequency charts
- Polar plots of the far field elevation and azimuth patterns
- Antenna gain
- All of these choices are correct

What is the front-to-back ratio of the radiation pattern shown in Figure E9-2?

How many elevation lobes appear in the forward direction of the antenna radiation pattern shown in Figure E9-2?