Key Topic 53: Oscillators & Modulators

Question 1

3-53G1: What is the modulation index in an FM phone signal having a maximum frequency deviation of 3,000 Hz on either side of the carrier frequency when the modulating frequency is 1,000 Hz?

A. 0.3
B. 3,000
C. 3
D. 1,000

Answer 1

C. 3

Question 2

3-53G2: What is the modulation index of a FM phone transmitter producing a maximum carrier deviation of 6 kHz when modulated with a 2 kHz modulating frequency?

A. 3
B. 6,000
C. 2,000
D. 1

Answer 2

A. 3

Question 3

3-53G3: What is the total bandwidth of a FM phone transmission having a 5 kHz deviation and 3 kHz modulating frequency?

A. 3 kHz
B. 8 kHz
C. 5 kHz
D. 16 kHz

Answer 3

D. 16 kHz

Question 4

3-53G4: How does the modulation index of a phase-modulated emission vary with RF carrier frequency?

A. It does not depend on the RF carrier frequency.
B. Modulation index increases as the RF carrier frequency increases.
C. It varies with the square root of the RF carrier frequency.
D. It decreases as the RF carrier frequency increases.

Answer 4

A. It does not depend on the RF carrier frequency.

Question 5

3-53G5: How can a single-sideband phone signal be generated?

A. By driving a product detector with a DSB signal.
B. By using a reactance modulator followed by a mixer.
C. By using a loop modulator followed by a mixer.
D. By using a balanced modulator followed by a filter.

Answer 5

D. By using a balanced modulator followed by a filter.

Question 6

3-53G6: What is a balanced modulator?

A. An FM modulator that produces a balanced deviation.
B. A modulator that produces a double sideband, suppressed carrier signal.
C. A modulator that produces a single sideband, suppressed carrier signal.
D. A modulator that produces a full carrier signal.

Answer 6

B. A modulator that produces a double sideband, suppressed carrier signal.