T9A-2014: Antennas: vertical and horizontal polarization; concept of gain; common portable and mobile antennas; relationships between antenna length and frequency
What is a beam antenna?
An antenna that concentrates signals in one direction
An antenna built from aluminum I-beams
An omnidirectional antenna invented by Clarence Beam
An antenna that reverses the phase of received signals
Which of the following is true regarding vertical antennas?
The electric field is perpendicular to the Earth
The magnetic field is perpendicular to the Earth
The phase is inverted
The phase is reversed
Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface?
A horizontally polarized antenna
A ground wave antenna
A rhombic antenna
A vertically polarized antenna
What is a disadvantage of the “rubber duck” antenna supplied with most handheld radio transceivers?
It does not transmit or receive as effectively as a full-sized antenna
It transmits a circularly polarized signal
If the rubber end cap is lost it will unravel very quickly
All of these choices are correct
How would you change a dipole antenna to make it resonant on a higher frequency?
Insert coils in series with radiating wires
Add capacitive loading to the ends of the radiating wires
What type of antennas are the quad, Yagi, and dish?
What is a good reason not to use a “rubber duck” antenna inside your car?
Signals can be significantly weaker than when it is outside of the vehicle
It might cause your radio to overheat
The SWR might decrease, decreasing the signal strength
All of these choices are correct
What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?
What is the approximate length, in inches, of a 6 meter 1/2-wavelength wire dipole antenna?
In which direction is the radiation strongest from a half-wave dipole antenna in free space?
Broadside to the antenna
Equally in all directions
Off the ends of the antenna
In the direction of the feed line
What is meant by the gain of an antenna?
The increase in signal strength in a specified direction when compared to a reference antenna
The additional power that is added to the transmitter power
The additional power that is lost in the antenna when transmitting on a higher frequency
The increase in impedance on receive or transmit compared to a reference antenna
What is a reason to use a properly mounted 5/8 wavelength antenna for VHF or UHF mobile service?
It offers a lower angle of radiation and more gain than a 1/4 wavelength antenna and usually provides improved coverage
It features a very high angle of radiation and is better for communicating via a repeater
The 5/8 wavelength antenna completely eliminates distortion caused by reflected signals
The 5/8 wavelength antenna offers a 10-times power gain over a 1/4 wavelength design
Why are VHF or UHF mobile antennas often mounted in the center of the vehicle roof?
A roof mounted antenna normally provides the most uniform radiation pattern
Roof mounts have the lowest possible SWR of any mounting configuration
Only roof mounting can guarantee a vertically polarized signal
Roof mounted antennas are always the easiest to install
Which of the following terms describes a type of loading when referring to an antenna?
Inserting an inductor in the radiating portion of the antenna to make it electrically longer
Inserting a resistor in the radiating portion of the antenna to make it resonant
Installing a spring at the base of the antenna to absorb the effects of collisions with other objects
Making the antenna heavier so it will resist wind effects when in motion
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