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Subelement L12
Receivers.
Section L12
In a frequency modulation receiver, the ________is connected to the input of the radio frequency amplifier.
  • frequency discriminator
  • limiter
  • Correct Answer
    antenna
  • mixer

Key words: "CONNECTED TO THE INPUT". In a receiver, an RF amplifier is generally used to amplify the tiny signal (i.e., microvolts) arriving from the Antenna. Once amplified, the incoming signal is fed to the Mixer.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a frequency modulation receiver, the __________ is in between the antenna and the mixer.
  • audio frequency amplifier
  • local oscillator
  • intermediate frequency amplifier
  • Correct Answer
    radio frequency amplifier

In a receiver, an RF amplifier is generally used to amplify the tiny signal (i.e., microvolts) arriving from the Antenna. Once amplified, the incoming signal is fed to the Mixer.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a frequency modulation receiver, the output of the local oscillator is fed to the:
  • limiter
  • antenna
  • Correct Answer
    mixer
  • radio frequency amplifier

The Mixer in a receiver takes in the incoming signal and mixes it with a local oscillator to transpose (usually down) the incoming signal to a fixed Intermediate Frequency (the Superheterodyne concept). Using a fixed and lower Intermediate Frequency regardless of operating frequency facilitates the achievement of high gain and selectivity.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a frequency modulation receiver, the output of the ________is connected to the mixer.
  • Correct Answer
    local oscillator
  • frequency discriminator
  • intermediate frequency amplifier
  • speaker or headphones

The Mixer in a receiver takes in the incoming signal and mixes it with a local oscillator to transpose (usually down) the incoming signal to a fixed Intermediate Frequency (the Superheterodyne concept). Using a fixed and lower Intermediate Frequency regardless of operating frequency facilitates the achievement of high gain and selectivity.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a frequency modulation receiver, the_________ is in between the mixer and the intermediate frequency amplifier.
  • limiter
  • frequency discriminator
  • radio frequency amplifier
  • Correct Answer
    filter

The Mixer accepts two inputs: the incoming signal and the local oscillator. Mixing returns two new products: the sum of the two inputs, the difference of the two inputs. The IF Filter seeks to let only one of the products into the Intermediate Frequency chain for amplification through the IF Amplifier.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a frequency modulation receiver, the ________ is located between the filter and the limiter.
  • local oscillator
  • mixer
  • radio frequency amplifier
  • Correct Answer
    intermediate frequency amplifier

The Mixer accepts two inputs: the incoming signal and the local oscillator. Mixing returns two new products: the sum of the two inputs, the difference of the two inputs. The IF Filter seeks to let only one of the products into the Intermediate Frequency chain for amplification through the IF Amplifier.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a frequency modulation receiver, the__________ is in between the intermediate frequency amplifier and the frequency discriminator.
  • Correct Answer
    limiter
  • filter
  • local oscillator
  • radio frequency amplifier

Detection (recovery of the original message) in a Frequency Modulation receiver is performed by the 'Discriminator'. The Discriminator translates frequency deviation back to audio. Early discriminators were sensitive to amplitude variations and needed to be preceded by a 'Limiter' to remove amplitude variations from the received signal. Limiters are integral part of an FM system as they cut down the influence of noise.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a frequency modulation receiver, the __________ is located between the limiter and the audio frequency amplifier.
  • Correct Answer
    frequency discriminator
  • intermediate frequency amplifier
  • speaker or headphones
  • local oscillator

Detection (recovery of the original message) in a Frequency Modulation receiver is performed by the 'Discriminator'. The Discriminator translates frequency deviation back to audio. Early discriminators were sensitive to amplitude variations and needed to be preceded by a 'Limiter' to remove amplitude variations from the received signal. Limiters are integral part of an FM system as they cut down the influence of noise.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a frequency modulation receiver, the _________ is located between the speaker or headphones and the frequency discriminator.
  • intermediate frequency amplifier
  • radio frequency amplifier
  • Correct Answer
    audio frequency amplifier
  • limiter

Most receivers rely on an Audio Amplifier to provide sufficient volume from the loudspeaker.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a frequency modulation receiver, the __________ connects to the audio frequency amplifier output.
  • limiter
  • Correct Answer
    speaker or headphones
  • intermediate frequency amplifier
  • frequency discriminator

key words: "CONNECTS TO". The expected answer relies on the general concept of connecting something to a source: a hose to a tap, a house to the electrical grid or gas mains. In that sense, the loudspeaker CONNECTS to the Audio Amplifier. The Audio Amplifier connects to the Discriminator.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a single sideband and CW receiver, the antenna is connected to the ____________ .
  • Correct Answer
    radio frequency amplifier
  • product detector
  • local oscillator
  • intermediate frequency amplifier

In a receiver, an RF amplifier is generally used to amplify the tiny signal (i.e., microvolts) arriving from the Antenna. Once amplified, the incoming signal is fed to the Mixer.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a single sideband and CW receiver, the output of the _____________ is connected to the mixer.
  • audio frequency amplifier
  • Correct Answer
    radio frequency amplifier
  • filter
  • intermediate frequency amplifier

The mixer accepts two inputs: the incoming signal and the local oscillator. Mixing returns two new products: the sum of the two inputs, the difference of the two inputs. The IF Filter seeks to let only one of the products into the Intermediate Frequency chain for amplification through the IF Amplifier.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a single sideband and CW receiver, the __________ is connected to the radio frequency amplifier and the local oscillator.
  • beat frequency oscillator
  • product detector
  • filter
  • Correct Answer
    mixer

The mixer accepts two inputs: the incoming signal and the local oscillator. Mixing returns two new products: the sum of the two inputs, the difference of the two inputs. The IF Filter seeks to let only one of the products into the Intermediate Frequency chain for amplification through the IF Amplifier.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a single sideband and CW receiver, the output of the ___________ is connected to the mixer.
  • product detector
  • Correct Answer
    local oscillator
  • intermediate frequency amplifier
  • beat frequency oscillator

The mixer accepts two inputs: the incoming signal and the local oscillator. Mixing returns two new products: the sum of the two inputs, the difference of the two inputs. The IF Filter seeks to let only one of the products into the Intermediate Frequency chain for amplification through the IF Amplifier.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a single sideband and CW receiver, the _____________ is in between the mixer and intermediate frequency amplifier.
  • Correct Answer
    filter
  • radio frequency amplifier
  • beat frequency oscillator
  • product detector

The mixer accepts two inputs: the incoming signal and the local oscillator. Mixing returns two new products: the sum of the two inputs, the difference of the two inputs. The IF Filter seeks to let only one of the products into the Intermediate Frequency chain for amplification through the IF Amplifier.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a single sideband and CW receiver, the __________ is in between the filter and product detector.
  • Correct Answer
    intermediate frequency amplifier
  • audio frequency amplifier
  • beat frequency oscillator
  • radio frequency amplifier

The mixer accepts two inputs: the incoming signal and the local oscillator. Mixing returns two new products: the sum of the two inputs, the difference of the two inputs. The IF Filter seeks to let only one of the products into the Intermediate Frequency chain for amplification through the IF Amplifier.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a single sideband and CW receiver, the __________ output is connected to the audio frequency amplifier.
  • beat frequency oscillator
  • intermediate frequency amplifier
  • Correct Answer
    product detector
  • local oscillator

In an SSB/CW receiver, detection (recovery of the message) is performed by a 'Product Detector'. The 'Product Detector' mixes the Intermediate Frequency signal with a Beat Frequency Oscillator to transpose the IF signal down to the audible range. The demodulated signal is applied to an Audio Amplifier to provide sufficient drive for the loudspeaker.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a single sideband and CW receiver, the output of the ___________ is connected to the product detector.
  • radio frequency amplifier
  • audio frequency amplifier
  • Correct Answer
    beat frequency oscillator
  • mixer

In an SSB/CW receiver, detection (recovery of the message) is performed by a 'Product Detector'. The 'Product Detector' mixes the Intermediate Frequency signal with a Beat Frequency Oscillator to transpose the IF signal down to the audible range. The demodulated signal is applied to an Audio Amplifier to provide sufficient drive for the loudspeaker.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a single sideband and CW receiver, the __________ is connected to the output of the product detector.
  • local oscillator
  • radio frequency amplifier
  • Correct Answer
    audio frequency amplifier
  • intermediate frequency amplifier

In an SSB/CW receiver, detection (recovery of the message) is performed by a 'Product Detector'. The 'Product Detector' mixes the Intermediate Frequency signal with a Beat Frequency Oscillator to transpose the IF signal down to the audible range. The demodulated signal is applied to an Audio Amplifier to provide sufficient drive for the loudspeaker.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a single sideband and CW receiver, the __________ is connected to the output of the audio frequency amplifier.
  • radio frequency amplifier
  • beat frequency oscillator
  • Correct Answer
    speaker or headphones
  • mixer

In an SSB/CW receiver, detection (recovery of the message) is performed by a 'Product Detector'. The 'Product Detector' mixes the Intermediate Frequency signal with a Beat Frequency Oscillator to transpose the IF signal down to the audible range. The demodulated signal is applied to an Audio Amplifier to provide sufficient drive for the loudspeaker.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Which list of emission types is in order from the narrowest bandwidth to the widest bandwidth?
  • CW, FM voice, RTTY, SSB voice
  • RTTY, CW, SSB voice, FM voice
  • Correct Answer
    CW, RTTY, SSB voice, FM voice
  • CW, SSB voice, RTTY, FM voice

In order of bandwidth requirements: CW = about 100 Hz, RTTY = about 600 Hz, SSB = 2 to 3 kHz, FM = 10 to 20 kHz.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

The figure in a receiver's specifications which indicates its sensitivity is the:
  • audio output in watts
  • bandwidth of the IF in kilohertz
  • number of RF amplifiers
  • Correct Answer
    RF input signal needed to achieve a given signal plus noise to noise ratio

A measurement of the 'Signal + Noise' to 'Noise' ratio shows how well an incoming signal overcomes the inherent internal noise of a receiver. A sensitive receiver will render more signal and little remaining noise (less background noise on the reproduced signal) when compared to the base noise in the receiver. Measuring how strong a signal is required to produce a given 'S+N/N' ratio permits comparing receiver sensitivities.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

If two receivers of different sensitivity are compared, the less sensitive receiver will produce:
  • a steady oscillator drift
  • more than one signal
  • more signal or less noise
  • Correct Answer
    less signal or more noise

key words: LESS SENSITIVE. A sensitive receiver will render more signal and little remaining noise (less background noise on the reproduced signal) when compared to the base noise in the receiver. The better receiver can render weak signals with little noise.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Which of the following modes of transmission is usually detected with a product detector?
  • Correct Answer
    Single sideband suppressed carrier
  • Double sideband full carrier
  • Frequency modulation
  • Pulse modulation

In SSB, the FREQUENCY of the original modulating signal is conveyed by the POSITION of each side frequency within the sideband in relation to the phantom carrier (it has been suppressed). A sideband (a group of ever changing side frequencies) is formed by the sum (Upper Sideband) or difference (Lower Sideband) of the modulating frequencies and the carrier frequency. The original frequency can only be reproduced correctly by "re-inserting" a reference signal, the Beat Frequency Oscillator, and mixing it with the received signal. 'Beat' is synonym of mixing.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

A receiver designed for SSB reception must have a BFO (beat frequency oscillator) because:
  • it beats with the received carrier to produce the other sideband
  • it reduces the passband of the IF stages
  • it phases out the unwanted sideband signal
  • Correct Answer
    the suppressed carrier must be replaced for detection

In SSB, the FREQUENCY of the original modulating signal is conveyed by the POSITION of each side frequency within the sideband in relation to the phantom carrier (it has been suppressed). A sideband (a group of ever changing side frequencies) is formed by the sum (Upper Sideband) or difference (Lower Sideband) of the modulating frequencies and the carrier frequency. The original frequency can only be reproduced correctly by "re-inserting" a reference signal, the Beat Frequency Oscillator, and mixing it with the received signal. 'Beat' is synonym of mixing.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

A receiver receives an incoming signal of 3.54 MHz, and the local oscillator produces a signal of 3.995 MHz. To which frequency should the IF be tuned?
  • 3.995 MHz
  • 3.54 MHz
  • Correct Answer
    455 kHz
  • 7.435 MHz

The mixer accepts two inputs: the incoming signal and the local oscillator. Mixing returns two new products: the sum of the two inputs, the difference of the two inputs. The IF Filter seeks to let only one of the products into the Intermediate Frequency chain for amplification through the IF Amplifier. In this example, 3995 kHz minus 3540 kHz yields 455 kHz.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What kind of filter would you use to attenuate an interfering carrier signal while receiving an SSB transmission?
  • An all pass filter
  • A pi-network filter
  • Correct Answer
    A notch filter
  • A band pass filter

The problem presented here is an offending signal within the receiver passband (the range of frequencies allowed though the Intermediate Frequency chain). A 'Notch Filter' which attenuates a very narrow range of frequencies can be used to remove the interfering carrier.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

The three main parameters against which the quality of a receiver is measured are:
  • selectivity, stability and frequency range
  • sensitivity, stability and cross-modulation
  • sensitivity, selectivity and image rejection
  • Correct Answer
    sensitivity, selectivity and stability

Three times letter S: Sensitivity, Selectivity and Stability. Sensitivity: render weak signals with less noise. Selectivity: the ability to separate signals from adjacent ones. Stability: staying on frequency over time despite temperature or voltage variations.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

A communications receiver has four filters installed in it, respectively designated as 250 Hz, 500 Hz, 2.4 kHz, and 6 kHz. If you were listening to single sideband, which filter would you utilize?
  • 6 kHz
  • 500 Hz
  • Correct Answer
    2.4 kHz
  • 250 Hz

In order of bandwidth requirements: CW = about 100 Hz, RTTY = about 600 Hz, SSB = 2 to 3 kHz, FM = 10 to 20 kHz. A 2.4 kHz filter is just wide enough to accept an SSB signal. Wider a filter, lets in more noise. Too narrow a filter causes distortion.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

A communications receiver has four filters installed in it, respectively designated as 250 Hz, 500 Hz, 2.4 kHz and 6 kHz. You are copying a CW transmission and there is a great deal of interference. Which one of the filters would you choose?
  • 2.4 kHz
  • 6 kHz
  • Correct Answer
    250 Hz
  • 500 Hz

In order of bandwidth requirements: CW = about 100 Hz, RTTY = about 600 Hz, SSB = 2 to 3 kHz, FM = 10 to 20 kHz. A 250 Hz filter is best to isolate a CW signal. Wider a filter, lets in more noise. Too narrow a filter causes distortion.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Selectivity can be placed in the audio stages of a receiver by the utilization of RC active or passive audio filters. If you were to copy CW, which of the following bandpasses would you choose?
  • 300 - 2700 Hz
  • 100 - 1100 Hz
  • Correct Answer
    750 - 850 Hz
  • 2100 - 2300 Hz

key words: AUDIO STAGES. After the 'Product Detector', an incoming CW signal is now an audible tone. Most receivers render CW as a note somewhere in the range of 750 Hz to 850 Hz. Additional band-pass filtering (allowing only a certain range of frequencies) can be useful to knock down adjacent stations finding their way into the receiver passband (the range of frequencies allowed though the Intermediate Frequency chain) and producing higher or lower notes, say at 250 or 1000 Hz.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

FM receivers perform in an unusual manner when two or more stations are present. The strongest signal, even though it is only two or three times stronger than the other signals, will be the only transmission demodulated. This is called:
  • surrender effect
  • Correct Answer
    capture effect
  • attach effect
  • interference effect

The 'Capture Effect' is specific to FM receivers: only the stronger of two signals at or near the same frequency will be demodulated. The complete suppression of the weaker signal occurs at the receiver limiter. When both signals are nearly equal in strength, or are fading independently, the receiver may switch from one to the other. http://en.wikipedia.org/

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

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