FM Radio Broadcasting

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Questions and Answers

What is the type of modulation scheme used in FM broadcasting?

Frequency modulation (correct)

Pulse width modulation

Amplitude modulation

Phase modulation

What is the maximum frequency deviation in FM transmission?

Occurs during the minimum positive peaks of the modulating signal

Occurs during the maximum positive and negative peaks of the modulating signal (correct)

Is directly proportional to the frequency of the modulating signal

Is inversely proportional to the amplitude of the modulating signal

What is the purpose of frequency deviation in FM transmission?

To reduce the bandwidth of the transmission

To vary the frequency of the carrier wave in proportion to the amplitude of the modulating signal (correct)

To shift the phase of the carrier wave

To increase the amplitude of the carrier wave

What is the effect of decreasing stereophonic separation?

The amount of crosstalk is increased Signup and view all the answers

What is the minimum frequency separation required between two FM broadcast stations in the same city or nearby cities?

800 kHz Signup and view all the answers

What is the minimum authorized transmitter power for a Class A station?

10 kW Signup and view all the answers

What is the maximum ERP allowed for a Class B station?

30 kW Signup and view all the answers

What is the limitation on the number of primary FM radio stations that a commercial broadcast entity can establish within the geographical boundary of any province?

One primary FM radio station Signup and view all the answers

What is the relationship between the instantaneous frequency deviation and the amplitude of the modulating signal in FM transmission?

Directly proportional Signup and view all the answers

What is the purpose of pre-emphasis in FM transmission?

To compensate for high-frequency losses in the transmission channel Signup and view all the answers

What is the minimum frequency separation required between two FM stations operating in the same locality?

800 kHz Signup and view all the answers

What is the purpose of phase deviation in FM transmission?

To shift the phase of the carrier wave Signup and view all the answers

What is the international and local standard for FM broadcasting?

ITU standard Signup and view all the answers

What is the maximum antenna height allowed for a Class B station?

500 feet Signup and view all the answers

What is the definition of 100% modulation in FM transmission?

Capable of producing ±75 kHz deviation Signup and view all the answers

What is the polarization allowed for FM broadcast stations?

Both horizontal and circular polarization Signup and view all the answers

What is the maximum carrier shift allowed at any percentage of modulation?

5% Signup and view all the answers

What is the frequency swing of the FM transmitter defined as?

100% modulation Signup and view all the answers

What is the Antenna Field Gain defined as?

The ratio of the effective free space field intensity produced at 1.6 km in the horizontal plane Signup and view all the answers

What is the Effective Radiated Power (ERP) of an FM transmitter?

The product of the transmitter power multiplied by the antenna power gain Signup and view all the answers

What is the Antenna Height Above Average Terrain (HAAT) defined as?

The height of the radiation center of the antenna above the terrain from 3 to 16 kilometers Signup and view all the answers

What is the center frequency of an FM transmitter?

The same as the carrier frequency Signup and view all the answers

What is the Antenna Power Gain defined as?

The antenna field gain in dB Signup and view all the answers

What is the purpose of the STL (Studio-to-Transmitter Link) in an FM broadcasting system?

To transmit the FM signal from the studio to the transmitter Signup and view all the answers

Study Notes

Frequency Modulation (FM)

FM is an angle modulation scheme where the frequency of a constant amplitude carrier varies in proportion to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal.

FM Waveform and Deviation

Frequency deviation is the amount of frequency shift that occurs when acted on by a modulating signal.
Maximum frequency deviation occurs during the maximum positive and negative peaks of the modulating signal.
Instantaneous frequency deviation is directly proportional to the amplitude of the modulation signal and inversely proportional to its frequency.

Station Classes and Power Limits

Class A Station: authorized transmitter power of 10 kW (minimum) up to 25 kW, ERP of 125 kW, antenna height limit of 2000 feet above average terrain, only allowed in Metro Manila and Cebu.
Class B Station: minimum power of 1 kW, maximum ERP of 30 kW, antenna height limit of 500 feet above average terrain.
Class C Station: non-commercial, community station with authorized radiated power not exceeding 1000 watts (ERP).
Class D Station: non-commercial station with power not exceeding 10 watts, educational stations fall under this class.

Frequency Separation and Spacing

Carrier frequency of two stations operating in the same locality should not have a difference of 10.6 MHz or 10.8 MHz.
FM broadcast stations operating in the same locality or nearby cities must not have a frequency separation of less than 800 kHz.

Transmission System and Standards

FM transmitter shall operate satisfactorily in the operating power range with frequency swing of +75 kHz, which is defined as 100% modulation.
Carrier shift at any percentage of modulation shall not exceed 5%.

FM Broadcasting and Transmission System

Components of an FM broadcasting and transmission system include: Studio-to-Transmitter Link (STL), Remote Pick-up Broadcast Station, Communications, Coordination and Control Link.

Antenna and Power Gain

Antenna Height Above Average Terrain (HAAT) is the height of the radiation center of the antenna above the terrain 3 to 16 kilometers from the antenna.
Antenna Field Gain is the ratio of the effective free space field intensity produced at 1.6-km in the horizontal plane expressed in mV/m for 1 KW antenna input power to 137.6 mV/m.
Antenna Power Gain is the square of the ratio of rms free space field strength produce at 1.6- km in the horizontal plane expressed in mV/m for 1 KW antenna input power to 137.6 mV/m.
Effective Radiated Power (ERP) is the product of the transmitter power multiplied by the antenna power gain or antenna field gain squared.

Center Frequency and Coverage

Center Frequency is the same as the carrier frequency.
FM coverage mapping and prediction are important aspects of FM studio and transmission design.

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Description

This quiz covers technical aspects of FM radio broadcasting, including stereophonic separation, injection ratio, and radio station classifications.