Which of the following can be used to generate FM phone signals?

1. A Balanced modulation of the audio amplifier
2. B Reactance modulation of a local oscillator
3. C Reactance modulation of the final amplifier
4. D Balanced modulation of a local oscillator

What is the function of a reactance modulator?

1. A Produce PM or FM signals by varying a resistance
2. B Produce AM signals by varying an inductance
3. C Produce AM signals by varying a resistance
4. D Produce PM or FM signals by varying a capacitance

What is a frequency discriminator?

1. A An FM generator circuit
2. B A circuit for filtering closely adjacent signals
3. C An automatic band-switching circuit
4. D A circuit for detecting FM signals

What is one way to produce a single-sideband phone signal?

1. A Use a balanced modulator followed by a filter
2. B Use a reactance modulator followed by a mixer
3. C Use a loop modulator followed by a mixer
4. D Use a product detector with a DSB signal

What is added to an FM speech channel to boost the higher audio frequencies?

1. A A de-emphasis network
2. B A harmonic enhancer
3. C A heterodyne enhancer
4. D A pre-emphasis network

Why is de-emphasis used in FM communications receivers?

1. A For compatibility with transmitters using phase modulation
2. B To reduce impulse noise reception
3. C For higher efficiency
4. D To remove third-order distortion products

What is meant by the term "baseband" in radio communications?

1. A The lowest frequency band that the transmitter or receiver covers
2. B The frequency range occupied by a message signal prior to modulation
3. C The unmodulated bandwidth of the transmitted signal
4. D The basic oscillator frequency in an FM transmitter that is multiplied to increase the deviation and carrier frequency

What are the principal frequencies that appear at the output of a mixer?

1. A Two and four times the input frequency
2. B The square root of the product of input frequencies
3. C The two input frequencies along with their sum and difference frequencies
4. D 1.414 and 0.707 times the input frequency

What occurs when the input signal levels to a mixer are too high?

1. A Spurious mixer products are generated
2. B Mixer blanking occurs
3. C Automatic limiting occurs
4. D Excessive AGC voltage levels are generated

How does a diode envelope detector function?

1. A By rectification and filtering of RF signals
2. B By breakdown of the Zener voltage
3. C By mixing signals with noise in the transition region of the diode
4. D By sensing the change of reactance in the diode with respect to frequency

Which type of detector is used for demodulating SSB signals?

1. A Discriminator
2. B Phase detector
3. C Product detector
4. D Phase comparator