# Extra Class Exam Question Pool

effective 7/01/2016 thru 6/29/2020

 Show: Unseen questions Weak questions Review questions Learned questions Incorrect answer choices

2016-E9C: Wire and phased array antennas: rhombic antennas; effects of ground reflections; e-off angles; Practical wire antennas: Zepps, OCFD, loops

2016-E9C01: What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase?

A figure-8 oriented along the axis of the array

Cardioid

Omni-directional

A figure-8 broadside to the axis of the array

2016-E9C02: What is the radiation pattern of two 1/4 wavelength vertical antennas spaced 1/4 wavelength apart and fed 90 degrees out of phase?

Cardioid

A figure-8 end-fire along the axis of the array

A figure-8 broadside to the axis of the array

Omni-directional

2016-E9C03: What is the radiation pattern of two 1/4 wavelength vertical antennas spaced a 1/2 wavelength apart and fed in phase?

A Figure-8 broadside to the axis of the array

Omni-directional

Cardioid

A Figure-8 end-fire along the axis of the array

2016-E9C04: What happens to the radiation pattern of an unterminated long wire antenna as the wire length is increased?

The lobes align more in the direction of the wire

The lobes become more perpendicular to the wire

The vertical angle increases

The front-to-back ratio decreases

2016-E9C05: What is an OCFD antenna?

A dipole feed approximately 1/3 the way from one end with a 4:1 balun to provide multiband operation

A remotely tunable dipole antenna using orthogonally controlled frequency diversity

An eight band dipole antenna using octophase filters

A multiband dipole antenna using one-way circular polarization for frequency diversity

2016-E9C06: What is the effect of a terminating resistor on a rhombic antenna?

It changes the radiation pattern from bidirectional to unidirectional

It reflects the standing waves on the antenna elements back to the transmitter

It changes the radiation pattern from horizontal to vertical polarization

It decreases the ground loss

2016-E9C07: What is the approximate feed point impedance at the center of a two-wire folded dipole antenna?

300 ohms

72 ohms

50 ohms

450 ohms

2016-E9C08: What is a folded dipole antenna?

A dipole consisting of one wavelength of wire forming a very thin loop

A dipole one-quarter wavelength long

A type of ground-plane antenna

A dipole configured to provide forward gain

2016-E9C09: What is a G5RV antenna?

A multi-band dipole antenna fed with coax and a balun through a selected length of open wire transmission line

A multi-band trap antenna

A phased array antenna consisting of multiple loops

A wide band dipole using shorted coaxial cable for the radiating elements and fed with a 4:1 balun

2016-E9C10: Which of the following describes a Zepp antenna?

An end fed dipole antenna

A dipole constructed from zip cord

An omni-directional antenna commonly used for satellite communications

A vertical array capable of quickly changing the direction of maximum radiation by changing phasing lines

2016-E9C11: How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus rocky ground?

Both the high-angle and low-angle radiation decrease

2016-E9C12: Which of the following describes an extended double Zepp antenna?

A center fed 1.25 wavelength antenna (two 5/8 wave elements in phase)

A wideband vertical antenna constructed from precisely tapered aluminum tubing

A portable antenna erected using two push support poles

An end fed folded dipole antenna

2016-E9C13: What is the main effect of placing a vertical antenna over an imperfect ground?

It causes increased SWR

It changes the impedance angle of the matching network

It reduces losses in the radiating portion of the antenna

2016-E9C14: How does the performance of a horizontally polarized antenna mounted on the side of a hill compare with the same antenna mounted on flat ground?

The main lobe takeoff angle decreases in the downhill direction

The main lobe takeoff angle increases in the downhill direction

The horizontal beam width decreases in the downhill direction

The horizontal beam width increases in the uphill direction

2016-E9C15: How does the radiation pattern of a horizontally polarized 3-element beam antenna vary with its height above ground?

The main lobe takeoff angle decreases with increasing height

The main lobe takeoff angle increases with increasing height

The horizontal beam width increases with height

The horizontal beam width decreases with height

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