Feedlines - Matching and Antennas
polarization, helical beam, parabolic antennas
What is meant by circularly polarized electromagnetic waves?
-
Waves with an electric field bent into circular shape
-
Waves that circle the earth
-
Waves produced by a circular loop antenna
-
Correct AnswerWaves with a rotating electric field
Tags: none
What is the polarization of an electromagnetic wave if its magnetic field is parallel to the surface of the Earth?
-
Elliptical
-
Circular
-
Correct AnswerVertical
-
Horizontal
Tags: none
What is the polarization of an electromagnetic wave if its magnetic field is perpendicular to the surface of the Earth?
-
Vertical
-
Circular
-
Elliptical
-
Correct AnswerHorizontal
Tags: none
The polarization of a radio wave is taken as the direction of the lines of force in the ________ field:
-
force
-
Correct Answerelectric
-
magnetic
-
electromagnetic
Tags: none
A transmitted wave is vertically polarized when:
-
Correct Answerits electrical component is vertical
-
the antenna is pointing north in the northern hemisphere
-
the antenna is parallel to the ground
-
its magnetic component is vertical
Tags: none
The polarisation of an antenna is the:
-
orientation of its radiated magnetic field
-
length of the radiating element
-
radiation angle
-
Correct Answerorientation of its radiated electric field
Tags: none
A parabolic antenna is very efficient because:
-
a dipole antenna can be used to pick up the received energy
-
no impedance matching is required
-
a horn-type radiator can be used to trap the received energy
-
Correct Answerall the received energy is focused to a point where the pick-up antenna is located
Tags: none
A helical-beam antenna with right-hand polarization will best receive signals with:
-
Correct Answerright-hand polarization
-
left-hand polarization
-
vertical polarization only
-
horizontal polarization
Tags: none
One antenna which will respond simultaneously to vertically-and horizontally-polarized signals is the:
-
Correct Answerhelical-beam antenna
-
folded dipole antenna
-
ground-plane antenna
-
quad antenna
Tags: none
What precaution should you take whenever you make adjustments to the feed system of a parabolic dish antenna?
-
Correct AnswerBe sure no one can activate the transmitter
-
Disconnect the antenna-positioning mechanism
-
Point the dish away from the sun so it doesn't concentrate solar energy on you
-
Be sure you and the antenna structure are properly grounded
Tags: none
Why should a protective fence be placed around the base of a ground-mounted parabolic dish transmitting antenna?
-
Correct AnswerTo reduce the possibility of persons being harmed by RF energy during transmissions
-
To reduce the possibility that animals will damage the antenna
-
To increase the property value through increased security awareness
-
To protect the antenna from lightning damage and provide a good ground system for the installation
Tags: none
View Privacy Policy | Get help with HamStudy.org™