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radio_basics [2015/11/19 14:28]
cwh0009 [Phase]
radio_basics [2015/11/19 14:47] (current)
cwh0009 [Wavelength]
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 The wavelength (λ) is the actual distance traveled by a wave in a single cycle. The wavelength is inversely related to the frequency. This means that as the wavelength increases, the frequency decreases, and as the wavelength decreases, the frequency increases. The wavelength (λ) is the actual distance traveled by a wave in a single cycle. The wavelength is inversely related to the frequency. This means that as the wavelength increases, the frequency decreases, and as the wavelength decreases, the frequency increases.
  
-^Wavelength |+Wave Wavelength |
 |{{:​wavelength.png}}| |{{:​wavelength.png}}|
 |Wavelength is measured by the distance it takes for a wave to complete a single cycle. A cycle is defined as the amount of space required for a wave to repeat itself. This can be determined from any point in the wave. The diagram above shows the wavelength measured from peak-to-peak,​ along the central axis, and trough-to-trough. All of these wavelengths are the same. | |Wavelength is measured by the distance it takes for a wave to complete a single cycle. A cycle is defined as the amount of space required for a wave to repeat itself. This can be determined from any point in the wave. The diagram above shows the wavelength measured from peak-to-peak,​ along the central axis, and trough-to-trough. All of these wavelengths are the same. |
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 If the voltage of an alternating current (AC) signal is measured with a simple voltmeter, the voltage reported is the RMS voltage. This is typically 120 V in the United States. The actual form of the wave can be examined using a tool called an oscilloscope. If the voltage of an alternating current (AC) signal is measured with a simple voltmeter, the voltage reported is the RMS voltage. This is typically 120 V in the United States. The actual form of the wave can be examined using a tool called an oscilloscope.
  
-^Amplitude |+^Wave Amplitude |
 |{{:​amplitude.png|}}| |{{:​amplitude.png|}}|
 |There are different methods of measuring the amplitude. The numbers indicated (1) the peak amplitude, (2) the peak-to-peak amplitude, (3) the root means square amplitude (RMS), and (4) the wavelength (which is not an amplitude). A standard AC electrical power outlet carries 120 Volts at 60 Hz. AC voltages are reported as root mean square voltages. The actual peak amplitude is about 170 Volts and the peak-to-peak voltage is about 340 Volts. | |There are different methods of measuring the amplitude. The numbers indicated (1) the peak amplitude, (2) the peak-to-peak amplitude, (3) the root means square amplitude (RMS), and (4) the wavelength (which is not an amplitude). A standard AC electrical power outlet carries 120 Volts at 60 Hz. AC voltages are reported as root mean square voltages. The actual peak amplitude is about 170 Volts and the peak-to-peak voltage is about 340 Volts. |
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 ==== Phase ==== ==== Phase ====
  
-Phase is a little more abstract than the previous three concepts. Phase is a measure of the starting angle of a trigonometric function. For example, a sine wave has an amplitude of 0 at 0°. A cosine wave has an amplitude of 1 at 0 degrees. A sine wave with a phase shift of 90° also has an amplitude of 1 at 0 degrees and is identical to an cosine wave. Mathematically, ​sin(x + 90°) = cos(x).+Phase is a little more abstract than the previous three concepts. Phase is a measure of the starting angle of a trigonometric function. For example, a sine wave has an amplitude of 0 at 0°. A cosine wave has an amplitude of 1 at 0 degrees. A sine wave with a phase shift of 90° also has an amplitude of 1 at 0 degrees and is identical to an cosine wave. This is represented by the expression ​sin(x + 90°) = cos(x).
  
-Phases of electrical signals are usually reported in relation to other signals.+----
  
-^Phase |+**Note:** If you are unfamiliar with trigonometric functions, you may wish to [[http://​www.visionlearning.com/​en/​library/​Math-in-Science/​62/​Wave-Mathematics/​131|review them]]. You will not be tested on them in the Technician exam, but an understanding of trigonometry is critical to many disciplines in engineering,​ science, and mathematics. In amateur radio, trigonometric functions are commonly used to express electromagnetic waves, model the behavior of circuits, and express methods of signal modulation. 
 + 
 +---- 
 + 
 +Phases of electrical signals represent a shift in time and are almost always reported in relation to other signals. Signals that have the same starting point have a phase shift of 0° relative to each other and are said to be //in phase//. Signals with a phase shift between them are said to be //out of phase// relative to each other. 
 + 
 +^Phase ​Shifts ​|
 |{{:​phase.png?​500|}}| |{{:​phase.png?​500|}}|
-|The phase (θ) of the blue signal is being measured relative to the red signal. In this example, the signal ​blue signal is a little less than 45° out of phase with the red signal.|+|The phase (θ) of the blue signal is being measured relative to the red signal. In this example, the blue signal is a little less than 45° out of phase with the red signal.|
 |Image credits: User [[https://​commons.wikimedia.org/​w/​index.php?​title=User:​Peppergrower|Peppergrower]]. [[https://​commons.wikimedia.org/​wiki/​File:​Phase_shift.svg|Wikimedia Commons]]. Image reused under a [[https://​creativecommons.org/​licenses/​by-sa/​3.0/​deed.en|CC BY-SA 3.0]] license. | |Image credits: User [[https://​commons.wikimedia.org/​w/​index.php?​title=User:​Peppergrower|Peppergrower]]. [[https://​commons.wikimedia.org/​wiki/​File:​Phase_shift.svg|Wikimedia Commons]]. Image reused under a [[https://​creativecommons.org/​licenses/​by-sa/​3.0/​deed.en|CC BY-SA 3.0]] license. |
 ==== Section Summary ==== ==== Section Summary ====
radio_basics.1447964934.txt.gz · Last modified: 2015/11/19 14:28 by cwh0009