Modulation - ESAT

Quartz crystal filter used in communication to improve.

Selectivity

Phase relationship between input signals fed to diodes.

180° out of phase

SSB compared to AM transmission

concentrated power

Overall sensitivity of receiver is limited

output power

Ability to still process weak signal

sensitivity

The receiver's ability to reject unwanted signals and receive the desired signal

selectivity

Two or more circuits within a receiver are varied by single control

gauged tuning

Used to transmit graph electronically

Fascimite

Circuit that is non-linear provide filtering and sensitive to type of

demodulator

Two types of electrical communication:

radio and wire

Intelligence produced by wire, radio, visual means.

Telecommunication

Characteristics of FM signal compared to AM signal

less static

Modulation index may be figured by

Df/fm

Plate modulators produce rf output by controlling

plate voltage

Where intelligence contained

frequency of the rf energy

Vertical axis on frequency spectrum graph

amplitude

Bandwidth of an AM wave

highest modulating frequency

Percentage of modulation for a modulated carrier wave

Em/Ec × 100

Over modulation of an AM signal will

increase

Purpose of transmitter machine

to increase the speed of communication

Advantage of cw communication

long-range operation

Amp tubes are added to the output of the transmitter

to increase power

Disadvantage of FM

consumes too much bandwidth

Why is modulation employed to carry-out reliable long-distance communication

To avoid the use of excessive long antennas and interference between signals

The bandwidth required for a modulated carrier depends on:

Baseband frequency range

When two or more signals share common channel, it is called:

Multiplexing

The power in the sidebands in AM system depends on:

Modulation index

Low level modulation is the process of generating the AM signal at low voltage and power and then using _______ to increase the power level

Linear amplifiers

What is double-sideband suppressed carrier modulation?

Power efficiency at the expense of complexity due to synchronization

Additional side frequencies produced by overmodulation or distortion in any AM system is known as:

Sideband splatter

In phase modulation, the carrier frequency deviation is proportional to:

Both the modulating frequency and amplitude of the modulating signal

Maximum deviation of PM signal occurs at:

Zero crossing point

When spectrum conservation is necessary, the bandwidth of an FM signal can be restricted by putting an upper limit on the:

Modulation index

Due to practical reason, bandwidth of FM transmissions is generally limited by:

Maximum frequency deviation and maximum modulating frequency

Tendency of an FM receiver to receive the strongest signal and reject others refers to:

Capture effect

A pre-emphasis circuit provides extra noise immunity by:

Artificial boosting of higher audio frequencies

Process of varying the characteristic of a wave (carrier signal) in accordance with message signal

Modulation

Modulation at the final or last stage

High level modulation

Modulation at stage earlier than final

Low level modulation

Is difficult to demodulate, since it requires that BOTH phase and frequency are sync at receiver

DSBSC

The only difference between audio signal of FM and analog TV broadcast is their:

Frequency deviation

What is the disadvantage of FM

Consumes too much bandwidth

Ability of the receiver to still process unwanted signal

Sensitivity

Ability of the receiver to reject unwanted signal

Selectivity

It acts as a high pass filter

Pre-emphasis

Act as low pass filter

De-emphasis

The lower the value, the better the selectivity (concept of selectivity)

Shape factor