Antenna Fundamentals in Radio and TV Engineering

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What is a radio signal composed of?

Protons and neutrons

Sound waves and light waves

Particles and energy

Electric and magnetic fields (correct)

What causes the electric and magnetic fields in an antenna?

Light shining on the antenna

Voltage applied to the antenna (correct)

Sound waves hitting the antenna

Heat applied to the antenna

How are the electric and magnetic fields oriented in a radio signal?

They are parallel to each other

They are at right angles to each other (correct)

They are in the same direction

They are in opposite directions

What is the speed at which electric and magnetic fields propagate through space?

The speed of light Signup and view all the answers

How are the polarities of the wires in a transmission line related?

They have opposite polarities Signup and view all the answers

Why do transmission lines not radiate radio signals efficiently?

They are not designed to radiate signals Signup and view all the answers

What is the measure of an antenna's directivity?

Beam width Signup and view all the answers

How is beam width measured on an antenna's radiation pattern?

Between points that are 3 dB down from the maximum amplitude Signup and view all the answers

What is antenna gain expressed as?

Ratio of effective radiated output power to input power Signup and view all the answers

What impedance does a dipole antenna have at its center?

73 ohms Signup and view all the answers

At what frequency does a dipole antenna appear to be a pure resistance of 73 ohms?

Resonant frequency Signup and view all the answers

What is important for maximum power transfer in a dipole antenna?

Matching the impedance of the transmission line to the load Signup and view all the answers

Which layer of the ionosphere is divided into the F1 and F2 layers?

The F layer Signup and view all the answers

What is the primary effect of the F layer on radio signals?

Refracting radio signals as they cross layer boundaries Signup and view all the answers

At what angle do radio signals pass directly through the ionosphere without being refracted?

$90^\circ$ Signup and view all the answers

Which layers of the ionosphere exist only during daylight hours?

The D and E layers Signup and view all the answers

What happens to radio signals at very high frequencies above 50 MHz?

They pass through the ionosphere without refraction Signup and view all the answers

What is the result of radio waves being reflected by the ionosphere?

The signal is propagated over an extremely long distance Signup and view all the answers

What is the relationship between the angles and indices of refraction called?

Snell's law Signup and view all the answers

What happens when an obstacle appears between a transmitter and receiver?

A shadow zone is created where some of the signal is blocked Signup and view all the answers

Which of the following is NOT one of the three basic paths that a radio signal can take through space?

Ionospheric wave Signup and view all the answers

What type of polarization is required for ground waves to be propagated from an antenna?

Vertical polarization Signup and view all the answers

In which frequency range are ground waves the main signal path?

30 kHz to 3 MHz Signup and view all the answers

What is the index of refraction for air, compared to the speed of a wave in a vacuum?

Very close to 1 Signup and view all the answers

What is the nature of the magnetic field generated by an antenna?

The magnetic field varies sinusoidally in accordance with the applied signal from the generator. Signup and view all the answers

What is the relationship between the electric and magnetic fields in an electromagnetic wave?

The electric and magnetic fields support and sustain each other in an electromagnetic wave. Signup and view all the answers

What is the wave impedance of space, which is the ratio of the electric field strength to the magnetic field strength of a radiated wave?

377 Ω Signup and view all the answers

At what speed are the resulting electromagnetic fields radiated into space?

The speed of light ($3 \times 10^8$ m/s) Signup and view all the answers

What is the role of the antenna radiation resistance in an antenna?

It represents the resistive component of the antenna that consumes power as radiated electromagnetic energy. Signup and view all the answers

What are the two sets of fields produced by an antenna?

The near field and the far field Signup and view all the answers