B45 - Transmitter and Receiver

Tx Rx reveiwer

In a superhetrodyne receiver, the difference frequency is chosen as the IF rather than the sum frequency because ____________.

Lower frequencies are easier to amplify

Modulation is done in __________.

Transmitter

Demodulation is done in ___________.

Radio receiver

A 50 kW carrier is to be amplitude modulated to a level of 85%.

What is the power in sidebands?

18.06 kW

Superhertodyne principle refers to

Obtaining lower fixed intermediate frequency

At 100% modulation, the power in each sideband is _________ of that of carrier

25%

In a transmitter ____________ oscillator is used

Crystal

If level of modulation is increased _____________ power is increased

Sideband

Overmodulation (amplitude) occurs when signal amplitude is ___________ carrier amplitude

greater than

If modulation is 100%, then signal amplitude is _____________ carrier

equal to

Man made noise are _________ variations.

Amplitude

In TV transmission, picture signal is ___________ modulated

Amplitude

In TV transmission, sound signal is __________ modulated

Frequency

Most of the amplification in a superhetrodyne receiver occurs at _________ stage.

IF

The superhetrodyne principle provides selectivity at _________ stage

IF

A high Q tuned circuit will permit an amplifier to have high __________.

Selectivity

If a radio receiver amplifies all the signal frequencies equally well, it is said to have high __________.

Fidelity

In an amplitude modulation, bandwidth is __________ the audio signal frequency

Twice

A 100 V carrier is made to vary between 160 V and 40 V by the signal. What is the modulation factor?

None of the above

In amplitude modulation, the __________ of carrier is varied according to the strength of the signal.

Amplitude

A 50 kW carrier is to be amplitude modulated to a level of 85%. What is the carrier power after modulation?

50 kW

The major advantage of FM over AM is ___________.

Reception is less noisy

In an AM wave, the majority of the power is in _________.

Carrier

As the modulation level is increased, the carrier power __________.

remains the same

Modulation refers to a low-frequency signal controlling the ________.

May be any of the above

In a radio receiver, noise is generally developed at __________.

RF stage

The diode detector in an AM radio receiver is usually found _________.

After several stages of amplification

The function of ferrite antenna is to __________.

Increase the Q of tuned circuit

If A_min = 40 and A_max = 60, what is the percentage of modulation?

Formula: (A_max - A_min)/(A_max + A_min)*100

20%

The signal voltage induced in the aerial of a radio receivers is of the order of ______________.

μV

In India, ____________ modulation is used for radio transmission

Amplitude

When modulating signal controls the frequency of the carrier, we get _________.

Frequency modulation

In an AM wave useful power is carrier by __________.

Sidebands

In a radio receiver, we generally use __________ oscillator as a local oscillator

Hartley

In radio transmission, the medium of transmission is ____________.

Space

In superhetrodyne receiver, the input at mixer stage is _____________.

RF and local oscillator signal

Overmodulation results in __________

Distortion

The letters AVC stand for ____________

Automatic volume control

In a TRF radio receiver, the RF and detection stages are tuned to ________.

Radio frequency

The IF is 455 kHz. If the radio receiver is tuned to 855 kHz, the local oscillator frequency is _________.

1310 kHz

Simple Receiver

Has only one tuned circuit to improve the selectivity of the antenna.

Fixed-Frequency Amplifier

An amplifier that boosts the intermediate frequency signal

Antenna

Is a selection of wire or a metallic device designed to intercept radio waves in the air and convert them to an electrical signal for feeding to a receiver.

Superheterodyne

Converts all input frequencies to a single, fixed, lower frequency which is amplified by fixed tuned circuits.

Local Oscillator

The output frequency of this stage is combined with the output frequency of the RF amplifier stage to produce a new frequency - the intermediate frequency

Detector

Is a device or circuit that extracts the information from a modulated carrier

Fidelity

The receivers’ ability to reproduce the intelligence of the signal.

Selectivity

A receivers’ ability to intercept a desired signal and extract its intelligence to the exclusion of others.

Tuned Radio Frequency Receiver

A receiver that can be placed after the detector as an audio amplifier, but it can also be added in the radio frequency stages prior to the detector.

Sensitivity

A receiver’s ability to intercept weak signals and extract intelligence from them.

Audio Frequency Amplifier

An amplifier that operates in part or all of the frequency range 20 Hz to 20 kHz.

Mixer

Is a special circuit that can mix two input signals together.

Receiver

Intercept some of the Radio Frequency (RF) energy radiated by the transmitter, separate the intelligence from the RF, and reproduce the intelligence as energy in some meaningful form, such as sound, light, or mechanical energy.

Low Level Transmitter

A transmitter circuit that does not require a large AF modulator power so its design is simplified.

Buffer Amplifier

Is used between one master oscillator and harmonic generator in AM-transmitter because it reduces S/N ratio.

Low Pass Filter

Is designed so that it passes frequencies that are lower than that of the stop band so in effect, signals above the cut-off frequency (fc) are reduced.

SSB

typically uses much lower power levels than are found in commercial AM broadcast transmitters as SSB is usually used for point-to-point communications.

Multimode Transmitter

The modulator may be switchable for AM, SSB and FM

Balanced Modulator/Mixer

is used to null the carrier for SSB

Direct Digital Synthesis

is a technique for producing an analog waveform by manipulating a fixed system clock digitally then running the output through a DAC. (DDS creates the sine wave using a Digital to Analogue Converter)