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Advanced Amateur A-006 Practice Exam
Practice Exam for Section A-006 of the ISED
Advanced Amateur Radio Examination
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What is one way receiver desensitization can be reduced?
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Use a cavity filter
Increase the transmitter audio gain
Decrease the receiver squelch gain
Increase the receiver bandwidth
What is the term for the reduction in receiver sensitivity caused by a strong signal near the received frequency?
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Desensitization
Squelch gain rollback
Quieting
Cross-modulation interference
What is meant by the noise floor of a receiver?
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The weakest signal that can be detected above the receiver internal noise
The amount of noise generated by the receiver local oscillator
The minimum level of noise that will overload the receiver RF amplifier stage
The weakest signal that can be detected under noisy atmospheric conditions
What causes intermodulation in an electronic circuit?
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Nonlinear circuits or devices
Positive feedback
Too little gain
Lack of neutralization
Poor frequency stability in a receiver usually originates in the:
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local oscillator and power supply
mixer
detector
RF amplifier
The noise generated in a receiver of good design originates in the:
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BFO and detector
detector and AF amplifier
RF amplifier and mixer
IF amplifier and detector
It is very important that the oscillators contained in a superheterodyne receiver are:
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stable and sensitive
selective and spectrally pure
sensitive and selective
stable and spectrally pure
Which two variables primarily determine the behaviour of an automatic gain control (AGC) loop?
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Clipping level and hang time
Blanking level and slope
Threshold and decay time
Slope and bandwidth
AGC voltage is applied to the:
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RF and AF amplifiers
detector and AF amplifiers
RF and IF amplifiers
AF and IF amplifiers
The term which relates specifically to the amplitude levels of multiple signals that can be accommodated during reception is called:
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cross-modulation index
noise figure
dynamic range
AGC
A multiple conversion superheterodyne receiver is more susceptible to spurious responses than a single-conversion receiver because of the:
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AGC being forced to work harder causing the stages concerned to overload
additional oscillators and mixing frequencies involved in the design
greater sensitivity introducing higher levels of RF to the receiver
poorer selectivity in the IF caused by the multitude of frequency changes
The first mixer in the receiver mixes the incoming signal with the local oscillator to produce:
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a high frequency oscillator (HFO) frequency
a radio frequency
an audio frequency
an intermediate frequency
What are the advantages of the frequency conversion process in a superheterodyne receiver?
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Automatic squelching and increased sensitivity
Increased selectivity and optimal tuned circuit design
Automatic soft-limiting and automatic squelching
Automatic detection in the RF amplifier and increased sensitivity
Which of these measurements is a good indicator of VHF receiver performance in an environment of strong out-of-band signals?
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Intermediate frequency rejection ratio
Third-Order Intercept Point
Blocking Dynamic Range
Two-tone Third-Order IMD Dynamic Range, 10 MHz spacing
The overall output of an AM/CW/SSB receiver can be adjusted by means of manual controls on the receiver or by use of a circuit known as:
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automatic gain control
automatic load control
inverse gain control
automatic frequency control
What factors should be considered when selecting an intermediate frequency?
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Noise figure and distortion
Cross-modulation distortion and interference
Interference to other services
Image rejection and responses to unwanted signals
Which of the following is NOT a direct cause of instability in a receiver?
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Temperature variations
Feedback components
Dial display accuracy
Mechanical rigidity
What does a product detector do?
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It amplifies and narrows band-pass frequencies
It provides local oscillations for input to a mixer
It detects cross-modulation products
It mixes an incoming signal with a locally generated carrier
The advantage of a double conversion receiver over a single conversion receiver is that it:
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is a more sensitive receiver
suffers less from image interference for a given front end sensitivity
does not drift off frequency
produces a louder audio signal
What is the primary purpose of an RF amplifier in a receiver?
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To vary the receiver image rejection by using the AGC
To provide most of the receiver gain
To develop the AGC voltage
To improve the receiver noise figure
The lower the receiver noise figure becomes, the greater will be the receiver's _________:
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sensitivity
stability
rejection of unwanted signals
selectivity
Intermodulation interference is produced by:
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the interaction of products from high-powered transmitters in the area
the mixing of more than one signal in the first or second intermediate frequency amplifiers of a receiver
the high-voltage stages in the final amplifier of an amplitude or frequency-modulated transmitter
the mixing of two or more signals in the front-end of a superheterodyne receiver
Which stage of a superheterodyne receiver lies between a tuneable stage and a fixed tuned stage?
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Intermediate frequency amplifier
Mixer
Local oscillator
Radio frequency amplifier
Distortion in a receiver that only affects strong signals usually indicates a defect in or mis-adjustment of the:
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RF amplifier
AF amplifier
automatic gain control (AGC)
IF amplifier
A double conversion receiver designed for SSB reception has a beat frequency oscillator and:
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two IF stages and three local oscillators
two IF stages and two local oscillators
one IF stage and one local oscillator
two IF stages and one local oscillator
In a superheterodyne receiver with automatic gain control (AGC), as the strength of the signal increases, the AGC:
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increases the receiver gain
distorts the signal
introduces limiting
reduces the receiver gain
Which of the following is a purpose of the first IF amplifier stage in a receiver?
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To increase dynamic response
To improve noise figure performance
To tune out cross-modulation distortion
To improve selectivity and gain
AGC is derived in a receiver from one of two circuits. Depending on the method used, it is called:
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IF derived or RF derived
RF derived or audio derived
IF derived or audio derived
detector derived or audio derived
In a communications receiver, a crystal filter would be located in the:
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local oscillator
detector
audio output stage
IF circuits
In a superheterodyne receiver, a stage before the IF amplifier has a variable capacitor in parallel with a trimmer capacitor and an inductance. The variable capacitor is for:
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tuning of the beat-frequency oscillator (BFO)
tuning both the antenna and the BFO
tuning of the local oscillator (LO)
tuning both the antenna and the LO
What is the term used for the decibel difference (or ratio) between the largest tolerable receiver input signal (without causing audible distortion products) and the minimum discernible signal (sensitivity)?
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Stability
Design parameter
Noise figure
Dynamic range
Which two stages in a superheterodyne receiver have input tuned circuits tuned to the same frequency?
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IF and local oscillator
RF and first mixer
RF and local oscillator
RF and IF
In a dual-conversion superheterodyne receiver what are the respective aims of the first and second conversion:
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selectivity and dynamic range
image rejection and noise figure
selectivity and image rejection
image rejection and selectivity
What receiver stage combines a 14.25-MHz input signal with a 13.795-MHz oscillator signal to produce a 455-kHz intermediate frequency (IF) signal?
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Multiplier
VFO
Mixer
BFO
Why are very low noise figures relatively unimportant for a high frequency receiver?
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Regardless of the front end, the succeeding stages when used on HF are very noisy
Ionospheric distortion of the received signal creates high noise levels
External HF noise, man-made and natural, are higher than the internal noise generated by the receiver
The use of SSB and CW on the HF bands overcomes the noise
The low-level output of a detector is:
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applied to the RF amplifier
applied to the AF amplifier
fed directly to the speaker
grounded via the chassis
The mixer stage of a superheterodyne receiver:
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produces spurious signals
produces an intermediate frequency
acts as a buffer stage
demodulates SSB signals
A superheterodyne receiver designed for SSB reception must have a beat-frequency oscillator (BFO) because:
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it reduces the pass-band of the IF stages
the suppressed carrier must be replaced for detection
it phases out the unwanted sideband signal
it beats with the receiver carrier to produce the missing sideband
Which of the following is an important reason for using a VHF intermediate frequency in an HF receiver?
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To prevent the generation of spurious mixer products
To tune out cross-modulation distortion
To provide a greater tuning range
To move the image response far away from the filter passband
If the incoming signal to the mixer is 3 600 kHz and the first IF is 9 MHz, at which one of the following frequencies would the local oscillator (LO) operate?
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3 400 kHz
21 600 kHz
10 600 kHz
5 400 kHz
The amplified IF signal is applied to the ____________ stage in a superheterodyne receiver:
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detector
RF amplifier
LO
audio output
How is receiver sensitivity often expressed for UHF FM receivers?
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Overall gain in decibels
Noise Figure in decibels
RF level for a given Bit Error Rate (BER)
RF level for 12 dB SINAD
What part of a superheterodyne receiver determines the image rejection ratio of the receiver?
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AGC loop
RF amplifier pre-selector
Product detector
IF filter
The BFO is off-set slightly (500 - 1 500 Hz) from the incoming signal to the detector. This is required:
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to pass the signal without interruption
to provide additional amplification
to beat with the incoming signal
to protect the incoming signal from interference
What causes receiver desensitization?
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Strong near frequency signals
Squelch gain adjusted too high
Squelch gain adjusted too low
Audio gain adjusted too low
The mixer stage of a superheterodyne receiver is used to:
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allow a number of IF frequencies to be used
remove image signals from the receiver
change the frequency of the incoming signal to that of the IF
produce an audio frequency for the speaker
Poor dynamic range of a receiver can cause many problems when a strong signal appears within or near the front-end bandpass. Which of the following is NOT caused as a direct result?
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Desensitization
Cross-modulation
Feedback
Intermodulation
One of the greatest advantages of the double-conversion over the single-conversion receiver is that it:
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greater reduction of image interference for a given front end selectivity
is much more sensitive
is much more stable
produces a louder signal at the output
What audio shaping network is added at an FM receiver to restore proportionally attenuated lower audio frequencies?
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A pre-emphasis network
An audio prescaler
A heterodyne suppressor
A de-emphasis network
Which stage of a receiver has its input and output circuits tuned to the received frequency?
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The detector
The RF amplifier
The local oscillator
The audio frequency amplifier
What circuit combines signals from an IF amplifier stage and a beat-frequency oscillator (BFO), to produce an audio signal?
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A product detector circuit
A VFO circuit
A power supply circuit
An AGC circuit
How much gain should be used in the RF amplifier stage of a receiver?
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Sufficient gain to keep weak signals below the noise of the first mixer stage
Sufficient gain to allow weak signals to overcome noise generated in the first mixer stage
It depends on the amplification factor of the first IF stage
As much gain as possible, short of self-oscillation
Normally, front-end selectivity is provided by the resonant networks both before and after the RF stage in a superheterodyne receiver. This whole section of the receiver is often referred to as the:
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preamplifier
preselector
pass-selector
preamble
A single conversion receiver with a 9 MHz IF has a local oscillator operating at 16 MHz. The frequency it is tuned to is:
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9 MHz
7 MHz
16 MHz
21 MHz
In a superheterodyne receiver without an RF amplifier, the input to the mixer stage has a variable capacitor in parallel with an inductance. The variable capacitor is for:
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tuning both the antenna and the beat-frequency oscillator
tuning the beat-frequency oscillator
tuning both the antenna and the local oscillator
tuning the receiver preselector to the reception frequency
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