Question 1

Varactor diodes are used for tuning by:
A) capacitance adjustment through forward bias.
B) capacitance adjustment through a reverse bias diode.
C) temperature compensation of diodes.
D) all of the above

Accepted Answer

Varactor diodes are specifically designed to allow their capacitance to be varied by changing the voltage applied in reverse bias. This property is utilized for tuning circuits, such as in radio frequency (RF) applications, by adjusting the capacitance to change the resonant frequency of the circuit.

Question 2

The diode detector:
A) one of the simplest and most effective AM detectors
B) is sometimes referred to as an envelope detector
C) consists of a nonlinear diode and low-pass filter
D) all of the above

Accepted Answer

The diode detector is indeed one of the simplest and most effective AM detectors, often referred to as an envelope detector, and it consists of a nonlinear diode and a low-pass filter, making all the given statements correct.

Question 3

In a varactor diode, as voltage increases, capacitance:
A) decreases
B) increases
C) stays the same
D) none of the above

Accepted Answer

A varactor diode's capacitance decreases as the reverse bias voltage applied to it increases. This is due to the widening of the depletion region, which effectively increases the distance between the "plates" (the p and n regions), reducing the capacitance.

Question 4

Image frequency rejection on a standard AM broadcast band receiver is not a major problem since:
A) the image frequency is not close to the IF frequency
B) the image frequency is so far away from the RF amplifier stage's tuned frequency
C) the image frequency is not produced by mixing action
D) the image frequency is not close to the LO frequency

Accepted Answer

The image frequency is significantly distant from the RF amplifier stage's tuned frequency in a standard AM broadcast band receiver, reducing its impact and making its rejection less of a concern. This distance allows the RF stage to effectively filter out the image frequency before it reaches the mixer stage.

Question 5

Which of the following is not an advantage of a synchronous detection?
A) Low distortion
B) Ability to produce gain
C) Eliminate diagonal clipping
D) ability to follow fast-modulated signals

Accepted Answer

Diagonal clipping is not an advantage of synchronous detection.

Question 6

A receiver's selectivity is:
A) the ability of a receiver to attenuate noise signals.
B) the extent to which a receiver is capable of differentiating between the desired signal and other signals.
C) its ability to drive the output speaker to an acceptable level.
D) the ability of the receiver to demodulate a modulated signal.

Accepted Answer

Selectivity refers to a receiver's ability to differentiate between the desired signal and other signals, particularly those close in frequency. This is crucial in crowded frequency environments to ensure clear reception of the intended transmission without interference from nearby channels.

Question 7

The only roadblock to having complete receivers on a chip aside from station selection and volume controls is:
A) IF amplifier.
B) limiting factors of tuned circuits.
C) local oscillator.
D) mixer circuits.

Accepted Answer

The limiting factors of tuned circuits are the primary roadblock to having complete receivers on a chip aside from station selection and volume controls. This is because the performance and selectivity of these circuits are difficult to replicate with the same level of quality and efficiency on a chip due to their physical properties and the need for precise tuning.

Question 8

Which is not an advantage of diode detectors?
A) They are highly efficient.
B) They develop a readily usable dc voltage for automatic gain control circuits.
C) Power absorbed from the tuned circuit by the diode detector reduces the Q of the tuned circuit.
D) Distortion decreases as the amplitude of the AM signal increases.

Accepted Answer

Diode detectors are known for their efficiency, ability to develop a DC voltage useful for automatic gain control circuits, and decreasing distortion with increasing AM signal amplitude. However, the power absorbed from the tuned circuit by the diode detector, which reduces the Q of the tuned circuit, is considered a disadvantage, not an advantage.

Question 9

A TRF receiver is to be designed with a single tuned circuit using an 8.2 uH inductor. If the frequency is to be tuned from 55 kHz to 1600 kHz, find the BW that results at 550 kHz if there is exactly 10 kHz BW at a frequency of 1050 kHz
A) 10 kHz
B) 15.24 kHz
C) 105 kHz
D) 5.24 kHz

Accepted Answer

The answer of A TRF receiver is to be designed...

Question 10

The mixer is often referred to as:
A) an RF amplifier.
B) a first detector.
C) an oscillator generator.
D) a second detector.

Accepted Answer

A mixer is commonly referred to as a first detector in radio frequency (RF) systems, where it is used to convert a signal from one frequency to another (usually from RF to IF or vice versa) by mixing it with a local oscillator signal.

Question 11

If a receiver is underselective:
A) more than one radio station on different frequencies may be picked up by the receiver at the same time
B) only part of the bandwidth of the AM signal is amplified, causing some of the sideband information to be lost and distortion results.
C) when the volume control is turned up to maximum, the desired station is very weak.
D) the tank circuits within the tuned amplifiers have too high a Q.

Accepted Answer

Underselectivity in a receiver means that its filter bandwidth is too wide, allowing it to pick up multiple stations on different frequencies simultaneously. This is because it cannot adequately discriminate between closely spaced signals.

Question 12

If a receiver is overly selective:
A) the volume control is turned up to maximum, the desired station is very weak.
B) only part of the bandwidth of the AM signal is amplified, causing some of the sideband information to be lost and distortion results.
C) too much noise is picked up and amplified by the receiver.
D) the tank circuits within the tuned amplifiers have insufficient Q.

Accepted Answer

When a receiver is overly selective, it means that its filtering is too narrow, leading to only part of the bandwidth of the AM signal being amplified. This causes some of the sideband information to be lost, resulting in distortion of the received signal.

Question 13

The radio receiver that simply consists of an RF amplifier, detector, and audio amplifier is known as:
A) a sensitive receiver
B) a selective receiver
C) a TRF receiver
D) a superheterodyne receiver

Accepted Answer

A TRF (Tuned Radio Frequency) receiver is characterized by its simplicity, consisting of an RF amplifier, detector, and audio amplifier. This design directly amplifies the incoming radio frequency signal through successive stages before detection and audio amplification, without the frequency conversion process used in superheterodyne receivers.

Question 14

A padder capacitor:
A) is placed in an RF amplifier to provide for proper neutralization.
B) is placed in a tank circuit to provide for electronic tuning.
C) is placed in parallel with each section of the ganged capacitors of the tank to provide tracking at the high end of a large frequency band.
D) is placed in series with the tank inductor to provide tracking at the low end of a large frequency band.

Accepted Answer

A padder capacitor is used in series with the tank inductor to adjust the tuning of the circuit at the low end of a frequency band, ensuring proper tracking across the band.

Question 15

Diagonal clipping:
A) is characterized by having the capacitor voltage not follow the full changes of the envelope of the AM waveform.
B) occurs if the time constant of the low-pass filter is too large compared to the period of the RF waveform.
C) is a type of distortion that occurs with diode detectors.
D) all of the above

Accepted Answer

Diagonal clipping is a distortion that occurs in AM (Amplitude Modulated) signal demodulation, particularly with diode detectors. It happens when the capacitor in the circuit does not fully follow the changes in the envelope of the AM waveform. This can be due to the time constant of the low-pass filter being too large in comparison to the period of the RF (Radio Frequency) waveform, leading to an inability to accurately track the envelope's variations.

Question 16

The superheterodyne receiver design is superior to the TRF design:
A) since it uses many RF amplifier stages before the RF signal is mixed with the local oscillator signal.
B) since it allows for a constant selectivity over the entire tuning range of the receiver.
C) since it always uses synchronous detectors instead of diode detectors.
D) all of the above

Accepted Answer

The superheterodyne receiver design is considered superior to the TRF (Tuned Radio Frequency) design primarily because it allows for constant selectivity over the entire tuning range of the receiver. This is achieved by converting all received signals to a common intermediate frequency (IF), where fixed-bandwidth filters can be used.

Question 17

A trimmer capacitor:
A) is placed in an RF amplifier to provide for proper neutralization.
B) is placed in series with the tank inductor to provide tracking at the low end of a large frequency band.
C) is placed in a tank circuit to provide for electronic tuning.
D) is placed in parallel with each section of the ganged capacitor of the tank to provide tracking at the high end of a large frequency band.

Accepted Answer

A trimmer capacitor is used to fine-tune the capacitance in a circuit, often placed in parallel with sections of a ganged capacitor to adjust and ensure proper tracking at the high end of a frequency band.

Question 18

Synchronous detectors:
A) offer low distortion compared to diode detectors.
B) have the ability to provide gain.
C) are often called product detectors.
D) all of the above

Accepted Answer

Synchronous detectors offer low distortion compared to diode detectors, have the ability to provide gain, and are often referred to as product detectors, making all the provided options correct.

Question 19

A receiver's sensitivity is:
A) its ability to drive the output speaker to an acceptable level.
B) the extent to which a receiver is capable of differentiating between the desired signal and other signals.
C) the ability of the receiver to demodulate a modulated signal.
D) the ability of a receiver to attenuate noise signals.

Accepted Answer

The answer of A receiver's sensitivity is:
A) its ability to...

Question 20

An AM signal having a carrier frequency of 560 kHz is to be mixed with a local oscillator signal at a frequency of 1035 kHz. What does the output of the IF amplifier consist of?
A) a 475 kHz sinewave
B) the original intelligence signal
C) a 455 kHz carrier
D) a 475 kHz AM signal

Accepted Answer

The output of the IF amplifier consists of a 475 kHz AM signal. This is because the IF amplifier is tuned to the difference between the carrier frequency and the local oscillator frequency, which in this case is 475 kHz. The AM signal is then demodulated to recover the original intelligence signal.

Quiz 3: Amplitude Modulation: Reception

Varactor diodes are used for tuning by:

The diode detector:

In a varactor diode, as voltage increases, capacitance:

Image frequency rejection on a standard AM broadcast band receiver is not a major problem since:

Which of the following is not an advantage of a synchronous detection?

A receiver's selectivity is:

The only roadblock to having complete receivers on a chip aside from station selection and volume controls is:

Which is not an advantage of diode detectors?

A TRF receiver is to be designed with a single tuned circuit using an 8.2 uH inductor. If the frequency is to be tuned from 55 kHz to 1600 kHz, find the BW that results at 550 kHz if there is exactly 10 kHz BW at a frequency of 1050 kHz

The mixer is often referred to as:

If a receiver is underselective:

If a receiver is overly selective:

The radio receiver that simply consists of an RF amplifier, detector, and audio amplifier is known as:

A padder capacitor:

Diagonal clipping:

The superheterodyne receiver design is superior to the TRF design:

A trimmer capacitor:

Synchronous detectors:

A receiver's sensitivity is:

An AM signal having a carrier frequency of 560 kHz is to be mixed with a local oscillator signal at a frequency of 1035 kHz. What does the output of the IF amplifier consist of?