GROL Receivers and Transmitters 2

Question 1

What is the primary purpose of the IF (intermediate frequency) stage in a superheterodyne receiver?

Accepted Answer

To provide fixed-frequency amplification and selectivity

Answer

To amplify the RF signal before mixing

Answer

To demodulate the incoming signal

Answer

To generate the local oscillator frequency

Question 2

In a superheterodyne receiver, the local oscillator frequency is typically offset from the incoming RF signal by:

Accepted Answer

The intermediate frequency (IF)

Answer

Exactly the audio bandwidth

Answer

Twice the carrier frequency

Answer

One-half the RF frequency

Question 3

What is the image frequency in a superheterodyne receiver?

Accepted Answer

A second RF frequency separated from the desired signal by twice the IF that also produces an IF output when mixed

Answer

A harmonic of the desired carrier

Answer

The mirror image of the audio output

Answer

The local oscillator frequency reflected back to the antenna

Question 4

Automatic Gain Control (AGC) in a receiver is designed to:

Accepted Answer

Maintain a relatively constant audio output level across a wide range of signal strengths

Answer

Automatically tune to the strongest available signal

Answer

Control the local oscillator frequency

Answer

Increase selectivity on weak signals

Question 5

The noise figure of a receiver is a measure of:

Accepted Answer

How much noise the receiver itself adds relative to the thermal noise floor

Answer

Background atmospheric noise at the antenna

Answer

The signal-to-noise ratio at the output

Answer

The minimum detectable signal at the antenna

Question 6

What is the purpose of a pre-selector (front-end bandpass filter) in a superheterodyne receiver?

Accepted Answer

To reject image frequencies and strong out-of-band signals before the mixer stage

Answer

To amplify weak signals before they reach the mixer

Answer

To provide audio frequency filtering

Answer

To stabilize the local oscillator

Question 7

In an FM receiver, the limiter stage that precedes the discriminator is used to:

Accepted Answer

Remove amplitude variations from the IF signal so only frequency variations reach the detector

Answer

Limit the audio output power to a safe level

Answer

Limit the deviation of the received signal

Answer

Prevent the squelch from activating on strong signals