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60 Cards in this Set
- Front
- Back
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3-41F1
What is the limiting condition for sensitivity in a communications receiver? |
The noise floor of the receiver
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3-41F2
What is the definition of the term “receiver desensitizing”? |
A reduction in receiver sensitivity because of a strong signal on a nearby frequency
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3-41F3
What is the term used to refer to a reduction in receiver sensitivity caused by unwanted high-level adjacent channel signals? |
Desensitizing
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3-41F4
What is meant by the term noise figure of a communications receiver? |
The level of noise generated in the front end and succeeding stages of a receiver
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3-41F5
Which stage of a receiver primarily establishes its noise figure? |
The RF stage
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3-41F6
What is the term for the ratio between the largest tolerable receiver input signal and the minimum discernible signal? |
Dynamic range
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3-42F1
How can selectivity be achieved in the front-end circuitry of a communications receiver? |
By using a preselector
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3-42F2
What is the primary purpose of an RF amplifier in a receiver? |
To improve the receiver’s noise figure
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3-42F3
How much gain should be used in the RF amplifier stage of a receiver? |
Sufficient gain to allow weak signals to overcome noise generated in the first mixer stage
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3-42F4
Too much gain in a VHF receiver front end could result in this: |
Susceptibility of intermodulation interference from nearby transmitters
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3-42F5
What is the advantage of a GaAsFET preamplifier in a modern VHF radio receiver? |
High gain and low noise floor
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3-42F6
In what stage of a VHF receiver would a low noise amplifier be most advantageous? |
Front end RF stage
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3-43F1
Why is the Colpitts oscillator circuit commonly used in a VFO (variable frequency oscillator)? |
It is stable
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3-43F2
What is the oscillator stage called in a frequency synthesizer? |
VCO
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3-43F3
What are three major oscillator circuits found in radio equipment? |
Colpitts, Hartley, and Pierce
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3-43F4
Which type of oscillator circuit is commonly used in a VFO (variable frequency oscillator)? |
Colpitts
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3-43F5
What condition must exist for a circuit to oscillate? It must: |
Have sufficient positive feedback
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3-43F6
In Figure 3F15, which block diagram symbol (labeled 1 through 4) is used to represent a local oscillator? |
2
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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? |
129.000 MHz
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3-44F2
What is the mixing process in a radio receiver? |
The combination of two signals to produce sum and difference frequencies
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3-44F3
In what radio stage is the image frequency normally rejected? |
RF
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3-44F4
What are the principal frequencies that appear at the output of a mixer circuit? |
The original frequencies and the sum and difference frequencies
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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? |
An image response
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3-44F6
What might occur in a receiver if excessive amounts of signal energy overdrive the mixer circuit? |
Spurious mixer products are generated
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3-45F1
What degree of selectivity is desirable in the IF circuitry of a wideband FM phone receiver? |
15 kHz
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3-45F2
Which one of these filters can be used in micro-miniature electronic circuits? |
Receiver SAW IF filter
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3-45F3
A receiver selectivity of 2.4 kHz in the IF circuitry is optimum for what type of signals? |
SSB voice
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3-45F4
A receiver selectivity of 10 KHz in the IF circuitry is optimum for what type of signals? |
Double-sideband AM
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3-45F5
What is an undesirable effect of using too wide a filter bandwidth in the IF section of a receiver? |
Undesired signals will reach the audio stage
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3-45F6
How should the filter bandwidth of a receiver IF section compare with the bandwidth of a received signal? |
Slightly greater than the received-signal bandwidth
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3-46F1
What is the primary purpose of the final IF amplifier stage in a receiver? |
Gain
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3-46F2
What factors should be considered when selecting an intermediate frequency? |
Image rejection and selectivity
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3-46F3
What is the primary purpose of the first IF amplifier stage in a receiver? |
Selectivity
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3-46F4
What parameter must be selected when designing an audio filter using an op-amp? |
Bandpass characteristics
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3-46F5
What are the distinguishing features of a Chebyshev filter? |
It allows ripple in the passband
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3-46F6
When would it be more desirable to use an m-derived filter over a constant-k filter? |
When you need more attenuation at a certain frequency that is too close to the cut-off frequency for a constant-k filter
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3-47F1
A good crystal band-pass filter for a single-sideband phone would be? |
2.1 KHz
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3-47F2
Which statement is true regarding the filter output characteristics shown in Figure 3F16? |
A is a low pass curve and D is a band stop curve
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3-47F3
What are the three general groupings of filters? |
High-pass, low-pass and band-pass
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3-47F4
What is an m-derived filter? |
A filter that uses a trap to attenuate undesired frequencies too near cutoff for a constant-k filter
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3-47F5
What is an advantage of a constant-k filter? |
It has high attenuation of signals at frequencies far removed from the pass band
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3-47F6
What are the distinguishing features of a Butterworth filter? |
It has a maximally flat response over its passband
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3-48F1
What is a product detector? |
It uses a mixing process with a locally generated carrier
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3-48F2
Which circuit is used to detect FM-phone signals? |
Frequency discriminator
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3-48F3
What is the process of detection in a radio diode detector circuit? |
Rectification and filtering of RF
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3-48F4
What is a frequency discriminator in a radio receiver? |
A circuit for detecting FM signals
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3-48F5
In a CTCSS controlled FM receiver, the CTCSS tone is filtered out after the: |
Discriminator but before the audio section
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3-48F6
What is the definition of detection in a radio receiver? |
The recovery of intelligence from the modulated RF signal
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3-49F1
What is the digital signal processing term for noise subtraction circuitry? |
Adaptive filtering and autocorrelation
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3-49F2
What is the purpose of de-emphasis in the receiver audio stage? |
When coupled with the transmitter pre-emphasis, flat audio and noise reduction is received
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3-49F3
What makes a Digital Coded Squelch work? |
Digital codes
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3-49F4
What causes a squelch circuit to function? |
Presence of noise
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3-49F5
What makes a CTCSS squelch work? |
Tones
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3-49F6
What radio circuit samples analog signals, records and processes them as numbers, then converts them back to analog signals? |
The digital signal processing circuit
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3-50F1
Where would you normally find a low-pass filter in a radio receiver? |
A and C, but not B
(A. In the AVC circuit. C. In the Power Supply.) |
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3-50F2
How can ferrite beads be used to suppress ignition noise? Install them: |
Install them in the primary and secondary ignition leads
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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? |
Cross-modulation interference
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3-50F4
What is cross-modulation interference? |
Modulation from an unwanted signal heard in addition to the desired signal
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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? |
4
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3-50F6
Pulse type interference to automobile radio receivers that appears related to the speed of the engine can often be reduced by: |
Installing resistances in series with spark plug wires
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