Power Content and Sidebands in Modulation

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Questions and Answers

What is the percent modulation of an AM wave if each of the sidebands contain 75 W and the total power content is 600 W?

75%

60%

81.6% (correct)

90%

In an AM wave, where is all the information contained?

Only in the carrier frequency

Equally distributed between carrier and sidebands

Only in the sidebands (correct)

More in the carrier frequency than the sidebands

In an SSB transmission containing 1 kW, how much power is contained in the sidebands?

0.5 kW

0.25 kW

1 kW (correct)

0.75 kW

What is the characteristic of suppressed carrier transmission?

Carrier power is completely removed Signup and view all the answers

In double-sideband transmission, how is the information distributed between upper and lower sidebands?

Both sidebands contain identical information Signup and view all the answers

If an SSB transmission contains 10 kW, how much power is at the carrier frequency?

0 kW Signup and view all the answers

What is the power content of the carrier in a single sideband transmission with 10 kW power and 80% modulation?

7575.76 W Signup and view all the answers

In a single sideband transmission with 10 kW power and 80% modulation, what is the power content of one of the sidebands?

1212.12 W Signup and view all the answers

If a standard amplitude modulated signal replaces an SSB transmission with the same power content, what will be the power content of the carrier and sidebands at 80% modulation?

Carrier: 7575.76 W, Sidebands: 1212.12 W Signup and view all the answers

How is the percent modulation determined using an oscilloscope?

By applying the modulated signal to the vertical input and the audio frequency modulating signal to the horizontal input Signup and view all the answers

What is the modulation factor if the percent modulation is found to be 60% using an oscilloscope?

0.6 Signup and view all the answers

If the percent modulation is determined to be 42.9% on an oscilloscope, what percentage does this value represent?

60% Signup and view all the answers

What is the formula to calculate the modulated wave in terms of voltage?

$Vc[1 + m\sin(2\pi f_mt)]\cos(2\pi f_ct)$ Signup and view all the answers

What is the modulation factor?

Defined as $m = \frac{fa}{fc}$ Signup and view all the answers

What happens when the percent modulation exceeds 100%?

Distortion occurs with extraneous frequencies Signup and view all the answers

What are the upper side and lower side frequencies called in a modulated wave?

$fc$ and $fc + fa$ Signup and view all the answers

For a broadcast station broadcasting frequencies from 0 to 5 kHz, what is the total bandwidth requirement?

10 kHz Signup and view all the answers

What does the formula $Pc = \frac{Vc^2}{2R}$ represent in the context of power content?

Power content of the unmodulated carrier Signup and view all the answers

Study Notes

Amplitude Modulation

Amplitude Modulation (AM) is a modulation technique used to transmit information through a carrier wave.
The power content of the carrier and each sideband can be calculated when the percent modulation is known.

Modulation Factor and Percent Modulation

Modulation factor (m) is defined as the ratio of the peak voltage of the modulating signal to the peak voltage of the unmodulated carrier.
Percent modulation (M) is the modulation factor expressed as a percentage.
M = 100% means the amplitude of the modulating signal is equal to the amplitude of the carrier.
Percent modulation can vary from 0 to 100% without introducing distortion, but beyond 100%, distortion occurs.

Components of the Modulated Wave

A modulated wave consists of a carrier wave and two sidebands: upper side frequency (fc + fa) and lower side frequency (fc - fa).
The bandwidth requirement for a broadcast station is twice the maximum frequency of the modulating signal.

Power Content

The power content of the carrier (Pc) and each sideband (PLSB and PUSB) can be calculated using the modulation factor.
The total power content of an AM wave is the sum of the power content of the carrier and the sidebands.

Ways of Maximizing Transmitted Power

Only 1/3 of the transmitted power is located in the sidebands, which contain the information.
The remaining 2/3 of the power is located in the carrier frequency, which contains no information.
Three ways to maximize transmitted power: • Suppressed carrier transmission • Double-sideband transmission • Single-sideband transmission

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Description

This quiz involves calculating the power content of the carrier and each sideband in a single sideband modulation transmission with 80% modulation. It also includes determining the power content of the carrier and sidebands in a standard amplitude modulated signal with the same power content.