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Subelement B-005

B-005

Section B-005-007

Section B-005-007

What is the term for the number of times per second an alternating current completes a positive to negative cycle?

  • Correct Answer
    Frequency
  • Speed
  • Pulse rate
  • Phase

Frequency is the number of cycles per second of an Alternating Current (AC). Frequency is expressed in hertz (Hz). One hertz is one cycle per second.

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

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What approximate range of frequencies can most humans hear?

  • Correct Answer
    20 Hz to 20 000 Hz
  • 300 Hz to 3 000 Hz
  • 20 Hz to 30 000 Hz
  • 200 Hz to 200 000 Hz

Hz = hertz = cycles per second. Frequencies audible to humans range from 20 Hz to 20 000 Hz. Speech frequencies important for intelligibility in communications range from 300 Hz to 3000 Hz.

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

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Why is the range of frequencies from 20 Hz to 20 kHz termed audio frequencies?

  • Because sound can be in this range but it's too low for RF signals
  • Because RF signals in this range can be directly converted to sound
  • Because this is the speaker response range of a modern SSB receiver
  • Correct Answer
    Because the human ear can sense sound in this range

Hz = hertz = cycles per second. Frequencies audible to humans range from 20 Hz to 20 000 Hz. Speech frequencies important for intelligibility in communications range from 300 Hz to 3000 Hz.

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

Tags: none

Electrical energy at a frequency of 7125 kHz is in what frequency range?

  • Very High Frequency (VHF)
  • Low Frequency (LF)
  • Correct Answer
    High Frequency (HF)
  • Medium frequency (MF)

Frequencies audible to humans range from 20 Hz to 20 000 Hz (AUDIO). Speech frequencies important for intelligibility in communications range from 300 Hz to 3000 Hz. Radio frequencies can reach up to 300 GHz ( 300 000 MHz ): Medium Frequencies 300 kHz to 3000 kHz, High Frequencies 3 MHz to 30 MHz, Very High Frequencies 30 MHz to 300 MHz, Ultra High Frequencies 300 MHz to 3000 MHz, Super High Frequencies 3 GHz to 30 GHz, Extremely High Frequencies 30 GHz to 300 GHz.

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

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What is the name for the distance an AC signal travels during one complete cycle?

  • Wave speed
  • Wave spread
  • Waveform
  • Correct Answer
    Wavelength

Wavelength: the distance between successive points of equal amplitude and phase on a wave (for example, crest to crest or trough to trough).

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

Tags: none

What happens to a signal's wavelength as its frequency increases?

  • Correct Answer
    It decreases
  • It decreases proportionally to frequency squared
  • It increases proportionally to frequency squared
  • It increases

Wavelength (lambda) in metres is 300 divided by frequency in megahertz ( i.e., the speed of light divided by the frequency in hertz ). Wavelength and frequency have an inverse relationship.

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

Tags: none

What happens to a signal's frequency as its wavelength gets shorter?

  • It increases proportionally to frequency squared
  • Correct Answer
    It increases
  • It decreases proportionally to frequency squared
  • It decreases

Wavelength (lambda) in metres is 300 divided by frequency in megahertz ( i.e., the speed of light divided by the frequency in hertz ). Wavelength and frequency have an inverse relationship.

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

Tags: none

What does 60 hertz (Hz) mean?

  • 60 metres per second
  • Correct Answer
    60 cycles per second
  • 6000 cycles per second
  • 6000 metres per second

Hz = hertz = cycles per second. Frequency is the number of cycles per second of an Alternating Current (AC). Frequency is expressed in hertz (Hz). One hertz is one cycle per second.

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

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Two AC waveforms have the same frequency, but their cycles do not begin at the same instant. What term describes that timing difference?

  • Delta
  • Offset
  • Correct Answer
    Phase
  • Polarity

Periodic signals, such as sine waves, of identical frequency that do not align time-wise are said to be "out of phase". A phase shift exists between them.

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

Tags: none

What is the shape of the waveform of the electricity supplied from a household receptacle?

  • Complex wave
  • Modified square wave
  • Pulse wave
  • Correct Answer
    Sine wave (sinusoidal)

The voltage, typically generated by alternators, follows a repeating (periodic) sinusoidal curve.

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

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A signal is composed of a fundamental frequency of 2 kHz and another of 4 kHz. What name is given to the 4 kHz signal?

  • Correct Answer
    Harmonic
  • Alias
  • Intermodulation
  • Sub-harmonic

'Harmonics' are integer MULTIPLES (e.g., 2x, 3x, 4x, 5x,...) of a given frequency. The base frequency is referred to as the 'fundamental'.

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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