Receivers

Key Topic 41:  Receiver Theory

3-41F1 What is the limiting condition for sensitivity in a communications receiver?

A. The noise floor of the receiver.

B. The power supply output ripple.

C. The two-tone intermodulation distortion.

D. The input impedance to the detector.

Receivers

Key Topic 41: Receiver Theory

3-41F2 What is the definition of the term “receiver desensitizing”?

A. A burst of noise when the squelch is set too low.

B. A reduction in receiver sensitivity because of a strong signal on a nearby frequency.

C. A burst of noise when the squelch is set too high.

D. A reduction in receiver sensitivity when the AF gain control is turned down.

Receivers

Key Topic 41: Receiver Theory

3-41F3 What is the term used to refer to a reduction in receiver sensitivity caused by unwanted high-level adjacent channel signals?

A. Desensitizing.

B. Intermodulation distortion.

C. Quieting.

D. Overloading.

Receivers

Key Topic 41: Receiver Theory

3-41F4 What is meant by the term noise figure of a communications receiver?

A. The level of noise entering the receiver from the antenna.

B. The relative strength of a received signal 3 kHz removed from the carrier frequency.

C. The level of noise generated in the front end and succeeding stages of a receiver.

D. The ability of a receiver to reject unwanted signals at frequencies close to the desired one.

Receivers

Key Topic 41: Receiver Theory

3-41F5 Which stage of a receiver primarily establishes its noise figure?

A. The audio stage.

B. The RF stage.

C. The IF strip.

D. The local oscillator.

Receivers

Key Topic 41: Receiver Theory

3-41F6 What is the term for the ratio between the largest tolerable receiver input signal and the minimum discernible signal?

A. Intermodulation distortion.

B. Noise floor.

C. Noise figure.

D. Dynamic range.

Receivers

Key Topic  42: RF Amplifiers

3-42F1 How can selectivity be achieved in the front-end circuitry of a communications receiver?

A. By using an audio filter.

B. By using an additional RF amplifier stage.

C. By using an additional IF amplifier stage.

D. By using a preselector.

Receivers

Key Topic 42: RF Amplifiers

3-42F2 What is the primary purpose of an RF amplifier in a receiver?

A. To provide most of the receiver gain.

B. To vary the receiver image rejection by utilizing the AGC.

C. To improve the receiver’s noise figure.

D. To develop the AGC voltage.

Receivers

Key Topic 42: RF Amplifiers

3-42F3 How much gain should be used in the RF amplifier stage of a receiver?

A. Sufficient gain to allow weak signals to overcome noise generated in the first mixer stage.

B. As much gain as possible short of self oscillation.

C. Sufficient gain to keep weak signals below the noise of the first mixer stage.

D. It depends on the amplification factor of the first IF stage.

Receivers

Key Topic 42: RF Amplifiers

3-42F4 Too much gain in a VHF receiver front end could result in this:

A. Local signals become weaker.

B. Difficult to match receiver impedances.

C. Dramatic increase in receiver current.

D. Susceptibility of intermodulation interference from nearby transmitters.

Receivers

Key Topic 42: RF Amplifiers

3-42F5 What is the advantage of a GaAsFET preamplifier in a modern VHF radio receiver?

A. Increased selectivity and flat gain.

B. Low gain but high selectivity.

C. High gain and low noise floor.

D. High gain with high noise floor.

Receivers

Key Topic 42: RF Amplifiers

3-42F6 In what stage of a VHF receiver would a low noise amplifier be most advantageous?

A. IF stage.

B. Front end RF stage.

C. Audio stage.

D. Power supply.

Receivers

Key Topic 43:  Oscillators

3-43F1 Why is the Colpitts oscillator circuit commonly used in a VFO (variable frequency oscillator)?

A. It can be phase locked.

B. It can be remotely tuned.

C. It is stable.

D. It has little or no effect on the crystal’s stability.

Receivers

Key Topic 43: Oscillators

3-43F2 What is the oscillator stage called in a frequency synthesizer?

A. VCO.
B. Divider.
C. Phase detector.
D. Reference standard.

Receivers

Key Topic 43: Oscillators

3-43F3 What are three major oscillator circuits found in radio equipment?

A. Taft, Pierce, and negative feedback.

B. Colpitts, Hartley, and Taft.

C. Taft, Hartley, and Pierce.

D. Colpitts, Hartley, and Pierce.

Receivers

Key Topic 43: Oscillators

3-43F4 Which type of oscillator circuit is commonly used in a VFO (variable frequency oscillator)?

A. Colpitts.

C. Hartley.

B. Pierce.

D. Negative feedback.

Receivers

Key Topic 43: Oscillators

3-43F5 What condition must exist for a circuit to oscillate? It must:

A. Have a gain of less than 1.

B. Be neutralized.

C. Have sufficient negative feedback.

D. Have sufficient positive feedback.

Receivers

Key Topic 43: Oscillators

3-43F6 In Figure 3F15, which block diagram symbol (labeled 1 through 4) is used to represent a local oscillator?

[image]

A. 1

B. 2

C. 3

D. 4

Receivers

Key Topic 44:  Mixers

3-44F1 What is the image frequency if the normal channel is 151.000 MHz, the IF is operating at 11.000 MHz, and the LO is at 140.000 MHz?

A. 131.000 MHz.

B. 129.000 MHz.

C. 162.000 MHz.

D. 150.000 MHz.

Receivers

Key Topic 44: Mixers

3-44F2 What is the mixing process in a radio receiver?

A. The elimination of noise in a wideband receiver by phase comparison.

B. The elimination of noise in a wideband receiver by phase differentiation.

C. Distortion caused by auroral propagation.

D. The combination of two signals to produce sum and difference frequencies.

Receivers

Key Topic 44: Mixers

3-44F3 In what radio stage is the image frequency normally rejected?

A. RF.

B. IF.

C. LO.

D. Detector.

Receivers

Key Topic 44: Mixers

3-44F4 What are the principal frequencies that appear at the output of a mixer circuit?

A. Two and four times the original frequency.

B. The sum, difference and square root of the input frequencies.

C. The original frequencies and the sum and difference frequencies.

D. 1.414 and 0.707 times the input frequency.

Receivers

Key Topic 44: Mixers

3-44F5 If a receiver mixes a 13.8 MHz VFO with a 14.255 MHz receive signal to produce a 455 kHz intermediate frequency signal, what type of interference will a 13.345 MHz signal produce in the receiver?

A. Local oscillator interference.

B. An image response.

C. Mixer interference.

D. Intermediate frequency interference.

Receivers

Key Topic 44: Mixers

3-44F6 What might occur in a receiver if excessive amounts of signal energy overdrive the mixer circuit?

A. Automatic limiting occurs.

B. Mixer blanking occurs.

C. Spurious mixer products are generated.

D. The mixer circuit becomes unstable and drifts.

Receivers

Key Topic 45:  IF Amplifiers

3-45F1 What degree of selectivity is desirable in the IF circuitry of a wideband FM phone receiver?

A. 1 kHz.

B. 2.4 kHz.

C. 4.2 kHz.

D. 15 kHz.

Receivers

Key Topic 45: IF Amplifiers

3-45F2 Which one of these filters can be used in micro-miniature electronic circuits?

A. High power transmitter cavity.

B. Receiver SAW IF filter.

C. Floppy disk controller.

D. Internet DSL to telephone line filter.

Receivers

Key Topic 45: IF Amplifiers

3-45F3 A receiver selectivity of 2.4 kHz in the IF circuitry is optimum for what type of signals?

A. CW.

B. Double-sideband AM voice.

C. SSB voice.

D. FSK RTTY.

Receivers

Key Topic 45: IF Amplifiers

3-45F4 A receiver selectivity of 10 KHz in the IF circuitry is optimum for what type of signals?

A. Double-sideband AM.

B. SSB voice.

C. CW.

D. FSK RTTY.

Receivers

Key Topic 45: IF Amplifiers

3-45F5 What is an undesirable effect of using too wide a filter bandwidth in the IF section of a receiver?

A. Output-offset overshoot.

B. Undesired signals will reach the audio stage.

C. Thermal-noise distortion.

D. Filter ringing.

Receivers

Key Topic 45: IF Amplifiers

3-45F6 How should the filter bandwidth of a receiver IF section compare with the bandwidth of a received signal?

A. Slightly greater than the received-signal bandwidth.

B. Approximately half the received-signal bandwidth.

C. Approximately two times the received-signal bandwidth.

D. Approximately four times the received-signal bandwidth.

Receivers

Key Topic 46:  Filters and IF Amplifiers

3-46F1 What is the primary purpose of the final IF amplifier stage in a receiver?

A. Dynamic response.

B. Gain.

C. Noise figure performance.

D. Bypass undesired signals.

Receivers

Key Topic 46: Filters and IF Amplifiers

3-46F2 What factors should be considered when selecting an intermediate frequency?

A. Cross-modulation distortion and interference.

B. Interference to other services.

C. Image rejection and selectivity.

D. Noise figure and distortion.

Receivers

Key Topic 46: Filters and IF Amplifiers

3-46F3 What is the primary purpose of the first IF amplifier stage in a receiver?

A. Noise figure performance.

B. Tune out cross-modulation distortion.

C. Dynamic response.

D. Selectivity.

Receivers

Key Topic 46: Filters and IF Amplifiers

3-46F4 What parameter must be selected when designing an audio filter using an op-amp?

A. Bandpass characteristics.

B. Desired current gain.

C. Temperature coefficient.

D. Output-offset overshoot.

Receivers

Key Topic 46: Filters and IF Amplifiers

3-46F5 What are the distinguishing features of a Chebyshev filter?

A. It has a maximally flat response over its passband.

B. It only requires inductors.

C. It allows ripple in the passband.

D. A filter whose product of the series- and shunt-element impedances is a constant for all frequencies.

Receivers

Key Topic 46: Filters and IF Amplifiers

3-46F6 When would it be more desirable to use an m-derived filter over a constant-k filter?

A. When the response must be maximally flat at one frequency.

B. When the number of components must be minimized.

C. When high power levels must be filtered.

D. When you need more attenuation at a certain frequency that is too close to the cut-off frequency for a constant-k filter.

Receivers

Key Topic 47:  Filters

3-47F1 A good crystal band-pass filter for a single-sideband phone would be?

A. 5 KHz.

B. 2.1 KHz.

C. 500 Hz.

D. 15 KHz.

Receivers

Key Topic 47: Filters

3-47F2 Which statement is true regarding the filter output characteristics shown in Figure 3F16?

[image]

A. C is a low pass curve and B is a band pass curve.

B. B is a high pass curve and D is a low pass curve.

C. A is a high pass curve and B is a low pass curve.

D. A is a low pass curve and D is a band stop curve.

Receivers

Key Topic 47: Filters

3-47F3 What are the three general groupings of filters?

A. High-pass, low-pass and band-pass.

B. Inductive, capacitive and resistive.

C. Audio, radio and capacitive.

D. Hartley, Colpitts and Pierce.

Receivers

Key Topic 47: Filters

3-47F4 What is an m-derived filter?

A. A filter whose input impedance varies widely over the design bandwidth.

B. A filter whose product of the series- and shunt-element impedances is a constant for all frequencies.

C. A filter whose schematic shape is the letter “M”.

D. A filter that uses a trap to attenuate undesired frequencies too near cutoff for a constant-k filter.

Receivers

Key Topic 47: Filters

3-47F5 What is an advantage of a constant-k filter?

A. It has high attenuation of signals at frequencies far removed from the pass band.

 B. It can match impedances over a wide range of frequencies.

C. It uses elliptic functions.

D. The ratio of the cutoff frequency to the trap frequency can be varied.

Receivers

Key Topic 47: Filters

3-47F6 What are the distinguishing features of a Butterworth filter?

A. A filter whose product of the series- and shunt-element impedances is a constant for all frequencies.

B. It only requires capacitors.

C. It has a maximally flat response over its passband.

D. It requires only inductors.

Receivers

Key Topic 48:  Detectors

3-48F1 What is a product detector?

A. It provides local oscillations for input to the mixer.

B. It amplifies and narrows the band-pass frequencies.

C. It uses a mixing process with a locally generated carrier.

D. It is used to detect cross-modulation products.

Receivers

Key Topic 48: Detectors

3-48F2 Which circuit is used to detect FM-phone signals?

A. Balanced modulator.

B. Frequency discriminator.

C. Product detector.

D. Phase splitter.

Receivers

Key Topic 48: Detectors

3-48F3 What is the process of detection in a radio diode detector circuit?

A. Breakdown of the Zener voltage.

B. Mixing with noise in the transition region of the diode.

C. Rectification and filtering of RF.

D. The change of reactance in the diode with respect to frequency.

Receivers

Key Topic 48: Detectors

3-48F4 What is a frequency discriminator in a radio receiver?

A. A circuit for detecting FM signals.

B. A circuit for filtering two closely adjacent signals.

C. An automatic band switching circuit.

D. An FM generator.

Receivers

Key Topic 48: Detectors

3-48F5 In a CTCSS controlled FM receiver, the CTCSS tone is filtered out after the:

A. IF stage but before the mixer.

B. Mixer but before the IF.

C. IF but before the discriminator.

D. Discriminator but before the audio section.

Receivers

Key Topic 48: Detectors

3-48F6 What is the definition of detection in a radio receiver?

A. The process of masking out the intelligence on a received carrier to make an S-meter operational.

B. The recovery of intelligence from the modulated RF signal.

C. The modulation of a carrier.

D. The mixing of noise with the received signal.

Receivers

Key Topic  49: Audio & Squelch Circuits

3-49F1 What is the digital signal processing term for noise subtraction circuitry?

A. Adaptive filtering and autocorrelation.

B. Noise blanking.

C. Noise limiting.

D. Auto squelch noise reduction.

Receivers

Key Topic 49: Audio & Squelch Circuits

3-49F2 What is the purpose of de-emphasis in the receiver audio stage?

A. When coupled with the transmitter pre-emphasis, flat audio is achieved.

B. When coupled with the transmitter pre-emphasis, flat audio and noise reduction is received.

C. No purpose is achieved.

D. To conserve bandwidth by squelching no-audio periods in the transmission.

Receivers

Key Topic 49: Audio & Squelch Circuits

3-49F3 What makes a Digital Coded Squelch work?

A. Noise.

B. Tones.

C. Absence of noise.

D. Digital codes.

Receivers

Key Topic 49: Audio & Squelch Circuits

3-49F4 What causes a squelch circuit to function?

A. Presence of noise.

B. Absence of noise.

C. Received tones.

D. Received digital codes.

Receivers

Key Topic 49: Audio & Squelch Circuits

3-49F5 What makes a CTCSS squelch work?

A. Noise.

B. Tones.

C. Absence of noise.

D. Digital codes.

Receivers

Key Topic 49: Audio & Squelch Circuits

3-49F6 What radio circuit samples analog signals, records and processes them as numbers, then converts them back to analog signals?

A. The pre-emphasis audio stage.

B. The squelch gate circuit.

C. The digital signal processing circuit.

D. The voltage controlled oscillator circuit.

C. The digital signal processing circuit.

Receivers

Key Topic 50:  Receiver Performance

3-50F1 Where would you normally find a low-pass filter in a radio receiver?

A. In the AVC circuit.

B. In the Oscillator stage.

C. In the Power Supply.

D. A and C, but not B.

Receivers

Key Topic 50: Receiver Performance

3-50F2 How can ferrite beads be used to suppress ignition noise? Install them:

A. In the resistive high voltage cable every 2 years.

B. Between the starter solenoid and the starter motor.

C. Install them in the primary and secondary ignition leads.

D. In the antenna lead.

C. Install them in the primary and secondary ignition leads.

Receivers

Key Topic 50: Receiver Performance

3-50F3 What is the term used to refer to the condition where the signals from a very strong station are superimposed on other signals being received?

A. Intermodulation distortion.

B. Cross-modulation interference.

C. Receiver quieting.

D. Capture effect.

B. Cross-modulation interference.

Receivers

Key Topic 50: Receiver Performance

3-50F4 What is cross-modulation interference?

A. Interference between two transmitters of different modulation type.

B. Interference caused by audio rectification in the receiver preamp.

C. Modulation from an unwanted signal heard in addition to the desired signal.

D. Harmonic distortion of the transmitted signal.

Receivers

Key Topic 50: Receiver Performance

3-50F5 In Figure 3F15 at what point in the circuit (labeled 1 through 4) could a DC voltmeter be used to monitor signal strength?

[image]

A. 1

B. 2

C. 3

D. 4

Receivers

Key Topic 50: Receiver Performance

3-50F6 Pulse type interference to automobile radio receivers that appears related to the speed of the engine can often be reduced by:

A. Installing resistances in series with spark plug wires.

B. Using heavy conductors between the starting battery and the starting motor.

C. Connecting resistances in series with the battery.

D. Grounding the negative side of the battery.

A. Installing resistances in series with spark plug wires.