Amplitude Modulation Transmission (Chapter 4)

Question 1

It is the process of changing the amplitude of relatively high frequency carrier signal in proportion with the instantaneous value of the modulating signal.

Answer 1

Amplitude Modulation (AM)

Question 2

It is a relatively inexpensive, low quality form of modulation that is used for commercial broadcasting of both audio and video signals. It is also used for for two-way mobile radio communications, such as Citizens band radio

Answer 2

Amplitude Modulation (AM)

Question 3

These are nonlinear devices with two inputs and one output

Answer 3

AM modulators

Question 4

What are frequencies tht are high enough to be efficiently radiated by an antenna and propagated through free space?

Answer 4

Radio Frequencies

Question 5

The modulated output waveform from an AM modulator is often called an _______

Answer 5

AM envelope

Question 6

The most commonly used amplitude modulation

Answer 6

Double-Sideband Full Carrier (DSBFC)

Question 7

In Amplitude Modulation, if there is no modulating signal, the output waveform is simply the carrier signal. True or False?

Answer 7

True

Question 8

For AM, the repitition rate of the envelope is _______ to the freqeuncy of the modulating signal

Answer 8

Equal

Question 9

The process of impressing low-frequency information signals

onto a high-frequency carrier signal.

Answer 9

Modulation

Question 10

The reverse process of modulation where the received signals

are transformed back to their original form.

Answer 10

Demodulation

Question 11

Sometimes called conventional AM or simply AM.

Answer 11

AM DSBFC

Question 12

The band of frequencies between fc – fm (max) and fc.

Answer 12

Lower sideband

Question 13

Any frequency within the lower sideband is called.

Answer 13

Lower Side frequency

Question 14

The band of frequencies between fc and fc + fm(max)

Answer 14

Upper Sideband

Question 15

Any frequency within the upper sideband is called?

Answer 15

Upper Side Frequency

Question 16

The term used to describe the amount of amplitude change

(modulation) present in an AM waveform signal.

Answer 16

Coefficient of Modulation

Question 17

The coefficient of modulation stated as a percentage.

Answer 17

Percent Modulation

Question 18

The maximum percent modulation that can be imposed without

causing excessive distortion.

Answer 18

100%

Question 19

The _______ in a transmitter where modulation occurs

determines whether the circuit is a low or a high-level transmitter.

Answer 19

Location

Question 20

The modulation takes place prior to the output element of the
final stage of the transmitter.

Answer 20

Low-level Modulation

Question 21

The modulation takes place in the final element of the final

stage where the carrier signal is at its maximum amplitude.

Answer 21

High-Level Modulation

Question 22

The amplitude of the output signal depends on the amplitude of
the input carrier and the voltage gain of the amplifier.

Answer 22

Emitter Modulation

Question 23

A class C modulator capable of nonlinear mixing and the
modulating signal is applied directly to the collector.

Answer 23

Collector Modulator

Question 24

Used to translate the low-frequency intelligence signals to
radio-frequency signals that can be efficiently radiated from an antenna and
propagated through free space.

Answer 24

Up-converter

Question 25

Are used for observing the modulation characteristics of AM

transmitters.

Answer 25

Trapezoidal Pattern

Question 26

A form of amplitude distortion introduced when the positive
and negative alternations in the AM modulated signal are not equal
(nonsymmetrical modulation).

Answer 26

Carrier Shift

Question 27

Complex waveforms comprised of two or more frequencies.

Answer 27

Nonsinusoidal Signals

Question 28

Are complex waves made up of two or more harmonically related
sine waves and include square, rectangular, and triangular waves.

Answer 28

Complex Repetitive

Waveforms

Question 29

A form of AM where signals from two separate information
sources modulate the same carrier frequency at the same time without
interfering with each other. The information sources modulate the same
carrier after it has been separated into two carrier signals that are 90º out
of phase with each other.

Answer 29

Quadrature Amplitude
Modulation
( QAM )