Radio and TV Engineering ECE 151 Lecture 3 Space Waves

Play an AI-generated podcast conversation about this lesson

What is the purpose of using repeater stations in communication at VHF, UHF, and microwave frequencies?

To decrease the range of transmission and reception
To reduce the need for tall buildings or mountains for antenna placement
To increase the directivity of antennas
To amplify and retransmit signals on different frequencies (correct)

Where are antennas for transmitters and receivers operating at very high frequencies typically located?

In underground tunnels
On flat plains
Underwater
On top of tall buildings or mountains (correct)

How is the output power of a transmitter typically determined?

By the type of antenna used
By measuring the directivity of the antenna
By calculating or measuring it (correct)
By the distance between the transmitter and receiver

What is one advantage of using microwave relay stations for long-distance communication?

They provide reliable communication over very long distances (A) Signup and view all the answers

What happens to a signal as it leaves an antenna in terms of attenuation?

Its attenuation is proportional to the square of the distance (D) Signup and view all the answers

What role do tall buildings or mountains play in increasing the range of transmission and reception for high-frequency antennas?

They provide elevation for better coverage (A) Signup and view all the answers

What is the primary method of radio signal propagation described in the text?

Space wave or direct wave propagation (A) Signup and view all the answers

What is the characteristic of space waves or direct waves according to the text?

They travel in a straight line directly from the transmitting antenna to the receiving antenna (B) Signup and view all the answers

What is the formula given in the text for computing the distance between a transmitting antenna and the horizon?

$D = 2.21 \sqrt{h_t}$ (A) Signup and view all the answers

What is the practical transmission distance for a transmitting antenna that is 350 ft high and a receiving antenna that is 25 ft high?

15.7 miles (D) Signup and view all the answers

What is the frequency range for which line-of-sight communication is characteristic according to the text?

Between 30 MHz and 300 MHz (C) Signup and view all the answers

Why must very high transmitting antennas be used for FM and TV broadcasts according to the text?

To ensure the signals pass through the ionosphere without being bent (D) Signup and view all the answers

What causes the variation in signal amplitude at the receiver known as fading?

Changes in the signal path characteristics (A) Signup and view all the answers

What happens to the received signal when a receiver gets farther away from a transmitter?

The signal gets weaker (C) Signup and view all the answers

What phenomenon causes fading when objects obstruct the path between a transmitter and receiver?

Shadow fading (D) Signup and view all the answers

How does shadow fading occur according to the text?

When large buildings or mountains come between the transmitter and receiver (B) Signup and view all the answers

What is the primary reason for the modification of the formula for power density from an isotropic radiator?

To account for fading effects (A) Signup and view all the answers

Why does the received signal vary in amplitude due to fading?

Due to changes in the environmental characteristics of the signal path (A) Signup and view all the answers