SWR - Revision history

Rider at 13:56, 24 October 2012

2012-10-24T13:56:37Z

← Older revision		Revision as of 06:56, 24 October 2012
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	==What is SWR?==		==What is SWR?==

	When there is a mismatch between the output impedance of a transmitter and input impedance of an antenna, some of the signal - in the form of a wave - is reflected back down the transmission line to the transmitter. Standing ~~waved~~ of electrical energy will "appear" in the transmission line. SWR is the ratio:		When there is a mismatch between the output impedance of a transmitter and input impedance of an antenna, some of the signal - in the form of a wave - is reflected back down the transmission line to the transmitter. Standing waves of electrical energy will "appear" in the transmission line. SWR is the ratio:

	Amplitude (height) of the standing wave : Amplitude of an adjacent node (central point on the wave form)		Amplitude (height) of the standing wave : Amplitude of an adjacent node (central point on the wave form)

2009-07-21T09:47:54Z

Some myths about SWR

← Older revision		Revision as of 02:47, 21 July 2009
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	* the TV station that your neighbour is watching is on a frequency that is a [[harmonics \|harmonic]] of your TX frequency		* the TV station that your neighbour is watching is on a frequency that is a [[harmonics \|harmonic]] of your TX frequency
	* you are using high power into a beam that is at the same height and directed towards your neighbours TV antenna		* you are using high power into a beam that is at the same height and directed towards your neighbours TV antenna

			5) I can reduce SWR by shortening my transmission line

			The length of a transmission line has no effect on SWR. The length of a transmission can affect the loss in power from the transmitter to the antenna, depending on the frequency of transmission and the type of line being used.

	==How is SWR calculated?==		==How is SWR calculated?==

2009-05-31T23:31:01Z

added info on vector sum

← Older revision		Revision as of 16:31, 31 May 2009
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	[[Image:Vk4yeh_swr.jpg \| 500px]]		[[Image:Vk4yeh_swr.jpg \| 500px]]

			If the forward and reflected wave coincide, the vector sum (the amplitude of the resultant wave) is effectively double the height of either of them.

			An excellent animation of the the vector sum of forward and reflected waves can be found [http://www.glenbrook.k12.il.us/gbssci/phys/Class/waves/u10l4b.html here]

	The most commonly used SWR measurement is '''Voltage''' SWR or VSWR. '''Current''' SWR or IVSWR is rarely used but provides the same information. The diagram above can be thought of as representing either voltage or current.		The most commonly used SWR measurement is '''Voltage''' SWR or VSWR. '''Current''' SWR or IVSWR is rarely used but provides the same information. The diagram above can be thought of as representing either voltage or current.

2009-04-09T00:59:29Z

How is SWR calculated?

← Older revision		Revision as of 17:59, 8 April 2009
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	[http://www.rac.ca/tca/SWR_Measurements.html Online SWR calculator] from VE3KL		[http://www.rac.ca/tca/SWR_Measurements.html Online SWR calculator] from VE3KL


			{{antennas}}

2008-08-26T07:45:31Z

fixed info

← Older revision		Revision as of 00:45, 26 August 2008
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	<math> P_f = </math> forward power - towards the antenna		<math> P_f = </math> forward power - towards the antenna

	==~~some~~ myths about SWR==		==Some myths about SWR==

	1) I can calculate SWR to a ratio of 1.000 : 1		1) I can calculate SWR to a ratio of 1.000 : 1
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	Your transmissions are most likely to interfere with other services when:		Your transmissions are most likely to interfere with other services when:
	* your transmitter puts out a broad band signal rather than a narrow band signal		* your transmitter puts out a broad band signal rather than a narrow band signal
	* the TV station that your neighbour is watching is on a frequency that is a harmonic of your TX frequency		* the TV station that your neighbour is watching is on a frequency that is a [[harmonics \|harmonic]] of your TX frequency
	* you are using high power into a beam that is at the same height ~~as you~~ neighbours TV antenna		* you are using high power into a beam that is at the same height and directed towards your neighbours TV antenna

	==How is SWR calculated?==		==How is SWR calculated?==

2008-08-24T06:55:32Z

new standing wave diagram

← Older revision		Revision as of 23:55, 23 August 2008
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	[[Image:~~Vk4yeh_standing_wave~~.jpg \| ~~300px~~]]		[[Image:Vk4yeh_swr.jpg \| 500px]]

	The most commonly used SWR measurement is '''Voltage''' SWR or VSWR. '''Current''' SWR or IVSWR is rarely used but provides the same information. The diagram above can be thought of as representing either voltage or current.		The most commonly used SWR measurement is '''Voltage''' SWR or VSWR. '''Current''' SWR or IVSWR is rarely used but provides the same information. The diagram above can be thought of as representing either voltage or current.

2008-08-23T00:57:13Z

added internal links

← Older revision		Revision as of 17:57, 22 August 2008
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	Related wiki pages [[Antennas]], [[Gain]], [[Propagation]], [[Bands]]		Related wiki pages [[Antennas]], [[Gain]], [[Propagation]], [[Bands]], [[harmonics]], [[Front-to-back ratio]]

2008-08-22T08:45:04Z

some myths about SWR

← Older revision		Revision as of 01:45, 22 August 2008
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	==some myths about SWR==		==some myths about SWR==

	* I can calculate SWR to a ratio of 1.000 : 1		1) I can calculate SWR to a ratio of 1.000 : 1

	Most instruments do not operate that this level of accuracy		Most instruments do not operate that this level of accuracy

	* High SWR is bad		2) High SWR is bad

	Look [http://www.vk1od.net/VSWR/VSWRMyths.htm here] for very detailed discussion about SWR		Look [http://www.vk1od.net/VSWR/VSWRMyths.htm here] for very detailed discussion about SWR

	* My SWR meter is the best on the market so is infallible		3) My SWR meter is the best on the market so is infallible

	Any instrument that is placed between the transmitter and the antenna changes the characteristics of the transmission line.		Any instrument that is placed between the transmitter and the antenna changes the characteristics of the transmission line.

	* High SWR will interfere with my neighbours TV		4) High SWR will interfere with my neighbours TV

	Your transmissions are most likely to interfere with other services when:		Your transmissions are most likely to interfere with other services when:

2008-08-22T08:37:54Z

added more info page needs expansion

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 <math> P_f = </math> forward power - towards the antenna
 ==How is SWR calculated?==
 [http://www.rac.ca/tca/SWR_Measurements.html Online SWR calculator] from VE3KL

2008-08-22T08:13:48Z

How is SWR related to forward and reflected power?

← Older revision		Revision as of 01:13, 22 August 2008
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	<math> E_r = </math> reflected voltage		<math> E_r = </math> reflected voltage

			<math> VSWR = \frac {1+ \sqrt (\frac{P_r}{P_f})}{ 1- \sqrt(\frac{P_r}{(P_f})} </math>

			where:

			<math> P_r = </math> reflected power

			<math> P_f = </math> forward power - towards the antenna

	==How is SWR calculated?==		==How is SWR calculated?==

	[http://www.rac.ca/tca/SWR_Measurements.html Online SWR calculator] from VE3KL		[http://www.rac.ca/tca/SWR_Measurements.html Online SWR calculator] from VE3KL