[EST] Frenzel Q&A - Chapter 4: Frequency Modulation

Amplitude

The amount of frequency deviation from the carrier center frequency in an FM transmitter is proportional to what characteristic of the modulating signal?

Angle

Both FM and PM are types of kind of modulation?

Decreases

If the amplitude of the modulating signal decreases, the carrier deviation __________.

Both positive and negative peak amplitude

On an FM signal, maximum deviation occurs at what point on the modulating signal?

Amplitude

In PM, a frequency shift occurs while what characteristic of the modulating signal is changing?

Zero crossing points

Maximum frequency deviation of a PM signal occurs at __________.

Carrier amplitude and frequency

In PM, carrier frequency deviation is not proportional to: __________.

Low-pass filter

To compensate for increases in carrier frequency deviation with an increase in modulating signal frequency, what circuit is used between the modulating signal and the phase modulator?

Indirect FM

The FM produced by PM is called __________.

The carrier frequency

If the amplitude of the modulating signal applied to a phase modulator is constant, the output signal will be

12.5

A 100 MHz carrier is deviated 50 kHz by a 4 kHz signal. The modulation index is __________.

5

The maximum deviation of an FM carrier is 2 kHz by a maximum modulating signal of 400 Hz. The deviation ratio is __________.

7

A 70 kHz carrier has a frequency deviation of 4 kHz with a 1000 Hz signal. How many significant sideband pairs are produced?

14 kHz

What is the bandwidth of the FM signal described in question 13 above?

0.11

What is the relative amplitude of the third pair of sidebands of an FM signal with m = 6?

10 kHz

A 200 kHz carrier is modulated by a 2.5 kHz signal. The fourth pair of sidebands are spaced from the carrier by __________.

48 kHz

An FM transmitter has a maximum deviation of 12 kHz and a maximum modulating frequency of 12 kHz. The bandwidth by Carson's rule is __________.

72%

The maximum allowed deviation of the FM sound signal in TV is 25 kHz. If the actual deviation is 18 kHz, the percent modulation is __________.

Lower complexity and cost

Which of the following is not a major benefit of FM over AM?

Excessive use of spectrum space

The primary disadvantage of FM is its __________.

High frequency spikes

Noise is primarily __________.

Limiter

The receiver circuit that rids FM of noise is the __________.

Capture effect

The phenomenon of a strong FM signal dominating a weaker signa on a common frequency is referred to as the __________.

Linear

The AM signals generated at a low level may only be amplified by what type of amplifier?

Class C

Frequency modulation transmitters are more efficient because their power is increased by what type of amplifier __________.

High frequencies

Noise interferes mainly with modulating signals that are __________.

High frequencies

Pre-emphasis circuits boost what modulating frequencies before modulation?

High pass filter

A pre-emphasis circuit is a __________.

Low-pass filter

Pre-emphasis is compensated for at the receiver by __________.

2.122 kHz

The cut-off frequency of pre-emphasis and de-emphasis circuits is __________.