Difference between revisions of "Frequency Wavelength and Period"
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==Wavelength== | ==Wavelength== | ||
| − | As indicated in the diagram above, the wavelength of a cyclic curve is the distance between adjacent corresponding points - peak to peak, trough to trough etc. For most ham radio applications, wavelength is measured in metres (m), centimetres (cm) or millimetres (mm). This is in fact how the [[Bands | amateur bands]] are described - eg 20m, | + | As indicated in the diagram above, the wavelength of a cyclic curve is the distance between adjacent corresponding points - peak to peak, trough to trough etc. For most ham radio applications, wavelength is measured in metres (m), centimetres (cm) or millimetres (mm). This is in fact how the [[Bands|amateur bands]] are described - eg 20m, 70 cm etc. |
==Frequency== | ==Frequency== | ||
Frequency is the number of corresponding wave points (eg peaks) that pass a stationary point each second. The unit for this is Hertz (HZ) or cycles per second. | Frequency is the number of corresponding wave points (eg peaks) that pass a stationary point each second. The unit for this is Hertz (HZ) or cycles per second. | ||
| − | * 1 [[KHz]] ([[Kilohertz]]) = 1000 Hz | + | * 1 [[KHz]] ([[Kilohertz]]) = 1000 Hz |
| − | * 1 [[MHz]] ([[Megahertz]]) = 1 000 000 Hz | + | * 1 [[MHz]] ([[Megahertz]]) = 1 000 000 Hz |
| − | * 1 [[GHz]] ([[Gigahertz]]) = 1 000 000 000 Hz | + | * 1 [[GHz]] ([[Gigahertz]]) = 1 000 000 000 Hz |
==Period== | ==Period== | ||
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|- | |- | ||
! Frequency | ! Frequency | ||
| − | | 1 mHz (10<sup> | + | | 1 mHz (10<sup>−3</sup>) |
| − | | 1 Hz (10<sup>0</sup>) | + | | 1 Hz (10<sup>0</sup>) |
| − | | 1 kHz (10<sup>3</sup>) || 1 MHz (10<sup>6</sup>) | + | | 1 kHz (10<sup>3</sup>) || 1 MHz (10<sup>6</sup>) |
| − | | 1 GHz (10<sup>9</sup>) || 1 THz (10<sup>12</sup>) | + | | 1 GHz (10<sup>9</sup>) || 1 THz (10<sup>12</sup>) |
|- | |- | ||
! Period (time) | ! Period (time) | ||
| 1 ks (10<sup>3</sup>) | | 1 ks (10<sup>3</sup>) | ||
| 1 s (10<sup>0</sup>) | | 1 s (10<sup>0</sup>) | ||
| − | | 1 ms (10<sup> | + | | 1 ms (10<sup>−3</sup>) || 1 µs (10<sup>−6</sup>) |
| − | | 1 ns (10<sup> | + | | 1 ns (10<sup>−9</sup>) || 1 ps (10<sup>−12</sup>) |
|} | |} | ||
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An harmonic of a particular frequency (the fundamental frequency '''f''') is another frequency that is an integer multiple of the first one. For example: | An harmonic of a particular frequency (the fundamental frequency '''f''') is another frequency that is an integer multiple of the first one. For example: | ||
| − | if f = | + | if f = 125 MHz, the harmonics would be: 2f = 250 MHz, 3f = 375 MHz, 4f = 500 MHz ..... etc |
| − | ==See | + | ==See also== |
* [[Modes]] | * [[Modes]] | ||
* [[Propagation]] | * [[Propagation]] | ||
Revision as of 22:53, June 27, 2016
What is a cyclic curve?
Frequency, Wavelength and Period refer to cyclic (repeating) waveforms. In ham radio we usually deal with sinusoidal (shaped like a sine curve), but many other repeating wave shapes are possible.
Mathematically, the basic wave equation is: Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \mathit{v}=\mathit{f}\times \lambda }
v is the velocity of the wave in metres per second - a constant close to the speed of light for radio waves in the atmosphere.
f is the frequency of the wave - how many cycles pass a fixed point per second
Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \lambda } is the wavelength of the wave in metres - the distance between two peaks of the wave.
So, as the frequency increases, the wavelength decreases - a doubling of frequency causes a halving of wavelength etc.
Wavelength
As indicated in the diagram above, the wavelength of a cyclic curve is the distance between adjacent corresponding points - peak to peak, trough to trough etc. For most ham radio applications, wavelength is measured in metres (m), centimetres (cm) or millimetres (mm). This is in fact how the amateur bands are described - eg 20m, 70 cm etc.
Frequency
Frequency is the number of corresponding wave points (eg peaks) that pass a stationary point each second. The unit for this is Hertz (HZ) or cycles per second.
Period
Period is the time taken for one complete cycle to pass a stationary point.
Period and Frequency
Radiowaves are usually described by their frequency (or by their wavelength when identifying an amateur band) rather than their period. The relationship between period and frequency is that they are the reciprocal of each other:
Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle T = \frac {1}{f} } and
Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle f = \frac {1}{T} } where
f = frequency in Hertz (Hz) and
T = the period in seconds
some comparisons between period and frequency are shown below.
| Frequency | 1 mHz (10−3) | 1 Hz (100) | 1 kHz (103) | 1 MHz (106) | 1 GHz (109) | 1 THz (1012) |
|---|---|---|---|---|---|---|
| Period (time) | 1 ks (103) | 1 s (100) | 1 ms (10−3) | 1 µs (10−6) | 1 ns (10−9) | 1 ps (10−12) |
What are Harmonics?
An harmonic of a particular frequency (the fundamental frequency f) is another frequency that is an integer multiple of the first one. For example:
if f = 125 MHz, the harmonics would be: 2f = 250 MHz, 3f = 375 MHz, 4f = 500 MHz ..... etc