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Topic: VSWR

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	Titre de page
		VSWR is by definition the report of the tension maximum HF with the minimum tension the long of a line of transmission; normally this report is valid only if it is measured between a maximum and an adjacent minimum because the most often we have affair with lines presenting losses.
		A fort VSWR of this departure is undesirable, mainly because it does not allow to load the transmitter correctly; more, loss HF in the line are increased notably if the former is long and presents a substantial loss coefficient.
		In summary, a weak VSWR is not a certain guarantee of a good radiation of the antenna and VSWR 1/1 does not entail automatically magical results ; when it is suitably interpreted, VSWR gives precious indications to the amateur, otherwise it will drive to losses of time and to vain discussions.
	licencera.free.fr /VSWR.html (533 words)

	EDN VSWR Calculator
		This uncertainty stems from the fact that, at high frequencies, the length of a transmission line connecting a source and load may be sufficient to transform the impedance at one end of the line to another value at the other end.
		VSWR is a common specification in data sheets for RF devices, such as amplifiers, sources, and power meters.
		Its VSWR is specified at 1.4 to 1.
	www.sonic.net /~shageman/vswr.html (898 words)

	VSWR
		Consequently, VSWR measurements on coax are usually made at the transmitter end of the feedline.
		Therefore you are presented with the VSWR of the entire system which includes all losses associated with the entire system.
		But let's assume that your VSWR measurement at the feedline is reasonably close to what is actually occurring on the feed line, and that your feedline losses are not great.
	www.antennex.com /preview/vswr.htm (2768 words)

	Exploit the power of VSWR measurements VSWR measurement, one of the most basic measures of RF system performance, lets ...
		VSWR is perhaps the simplest qualifier of system health, and it can yield important information about whether or not that health is deteriorating.
		VSWR is the ratio of power that is sent forward to the antenna to the amount of that power that is reflected back toward the transmitter because of standing waves on the transmission line and the terminating load, the antenna.
		In addition, making VSWR measurements on the receive section requires injecting a signal onto the line, which, if done manually, shuts down that sector until the measurement is made, which in turn halts communication in that sector while the test set-up is being installed and the receive antenna feed measurement is being made.
	mrtmag.com /mag/radio_exploit_power_vswr/index.html (1930 words)

	October Topic: VSWR (Site not responding. Last check: 2007-10-22)
		VSWR (voltage-standing-wave-ratio) represents the degree with which an antenna is "matched" to the system impedance.
		VSWR is one of the easiest parameters to measure and VSWR meters are becoming very popular antenna installation tools.
		A VSWR of 2:1 or greater usually is considered unacceptable (or for receiving purposes only) since it increases losses in the transmission line.
	www.astronantennas.com /OctoberTopicVSWR.html (221 words)

	Radiall-Larsen Antenna Technologies : Technical Reference : Basic Antenna Concepts
		A high VSWR is an indication the signal is reflected prior to being radiated by the antenna.
		VSWR and reflected power are different ways of measuring and expressing the same thing.
		Based on a 100 watt radio, a 1.5:1 VSWR equates to a forward power of 96 watts and a reflected power of 4 watts, or the reflected power is 4.2% of the forward power.
	www.radialllarsen.com /technicalreference_basicantennaconcepts.htm (2731 words)

	VSWR calculator help
		VSWR meters with adjustable sensitivity have a potential problem with scale linearity, they tend to be calibrated (ie the scale shape) for low sensitivity, and when readings are made at high sensitivity, the low readings will be underestimated.
		Indeed, in my observations such instruments are likely to introduce more VSWR than that, I have observed insertion VSWR (the VSWR caused by inserting the device in a line to a dummy load) as high as 1.5 at the high end of the claimed frequency range of the instrument.
		If low VSWR is required to meet the transmitter's requirement for a load impedance, high VSWR may limit the power than can be obtained from the transmitter and could cause the transmitter power amplifier to operate outside the designed safe limits or to activate protection circuits and reduce output power in a controlled way.
	www.vk1od.net /tl/vswrch.htm (2330 words)

	A.R.E.S. Niagara - Tech Note 15 - More VSWR (Site not responding. Last check: 2007-10-22)
		VSWR is merely a ratio between the two wave levels, enabling us to see the degree of mismatch between the line and load.
		The greater the VSWR is, the greater is the mismatch between line and load (antenna).
		If the VSWR at the load is not greater than 2, the additional loss caused by the standing waves, as compared with the loss when the line is perfectly matched, does not amount to more than about ½ dB even on very long lines.
	www.qsl.net /va3nag/tecnotes/tecnote15.html (1410 words)

	Jpole
		The circle of constant VSWR is unchanged by the conversion from impedance to admittance coordinates, and this circle is again drawn in fig 3.
		Measure the VSWR and shorten the length of the dipole element in small increments until a near 1 to 1 match is achieved.
		Measure and record the VSWR at several frequencies near where it was found to be lowest, and determine the precise frequency (F2) where it is equivalent to that of the dummy load alone.
	free.prohosting.com /~w0rcy/Jpole/jpole.html (14931 words)

	Voltage standing wave ratio (Site not responding. Last check: 2007-10-22)
		Voltage standing wave ratio (VSWR): In a transmission line, the ratio of maximum to minimum voltage in a standing wave pattern.
		Note: The VSWR is a measure of impedance mismatch between the transmission line and its load.
		The VSWR is also defined as the ratio of Maximum voltage to minimum voltage in a transmission medium.
	www.portaljuice.com /voltage_standing_wave_ratio.html (154 words)

	A.R.E.S. Niagara - Tech Note 11 - VSWR Etc (Site not responding. Last check: 2007-10-22)
		At the transmitter output with one of the modern transceivers we have a conjugate* condition between the transmitter and the feedline.
		Pruning the coaxial cable length does not change the vswr, it will merely change the impedance reflected from the antenna and sometimes to a value that is easier for the transmitter to match.
		At VHF and UHF, VSWR does present greater loss problems and since this is where the majority of the new hams start out today, all the mythology and baggage about VSWR acquired there is dragged to HF operation.
	www.qsl.net /va3nag/tecnotes/tecnote11.html (1739 words)

	How is your VSWR?
		VSWR facts of life A transmission line is considered to be a long series of inductances with parallel capacitors (as shown in Figure 1).
		A VSWR reading of 1.1:1, or about 5 percent reflected signal, is usually the maximum that can be safely handled, although most situations are different.
		VSWR and FM The average FM installation is far more susceptible to the effects of high VSWR.
	beradio.com /departments/radio_vswr/index.html (1157 words)

	Brushing Up on VSWR
		VSWR, or voltage standing wave ratio, is a measure of how well the components of the RF network are matched in impedance.
		Textbook VSWR VSWR is defined as the ratio of the maximum voltage to the minimum voltage in the standing wave.
		Hands-on VSWR It is relatively easy to measure return loss by using a common spectrum analyzer/tracking generator and then calculating the value of VSWR.
	wirelessreview.com /mag/wireless_brushing_vswr/index.html (1129 words)

	VSWR adaptive power amplifier system - Patent 5081425
		Under high VSWR conditions, power reflected by the load is absorbed in a dump port termination.
		Other techniques use a VSWR detection circuit to monitor the load status and provide a control signal to initiate the reduction of the power output of the amplifier to a safe operating value.
		The load is a 3 to 1 VSWR load and the dual output of Q1 and Q3 equals 125 watts total.
	www.freepatentsonline.com /5081425.html (2186 words)

	Moonraker Antenna Systems
		High VSWR indicates mismatch, which means increased power losses and less radiated signal, making it impossible for your transmitter to perform as well as it should.
		Cheaper VSWR meters measure the forward and reflected line voltage between the antenna and transmitter to determine an approximate VSWR measurement and this is adequate for most installation purposes.
		If you find different VSWR readings depending on where you insert the meter in the line, this normally is indicative of standing waves on the line and a mismatched antenna.
	www.moonraker.com.au /techni/matching.htm (1075 words)

	Standing wave ratio -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-22)
		The SWR is usually defined as a voltage ratio called the VSWR, for voltage standing wave ratio.
		For the calculation of VSWR, only the (The property of relative size or extent) magnitude of Γ, denoted by ρ, is of interest.
		The SWR can also be defined as the ratio of the maximum amplitude of the (Click link for more info and facts about electric field strength) electric field strength to its minimum amplitude, i.e.
	www.absoluteastronomy.com /encyclopedia/s/st/standing_wave_ratio.htm (840 words)

	Communication & Signal Processing engineering - VSWR
		VSWR is a funny (strange) measure as you can’t really use it directly in many cases.
		VSWR does not contain the phase information of the reflection coefficient so therefore all you can get is a worst case answer, not necessarily a representative answer.
		The VSWR for the connectors are not specified.
	www.eng-tips.com /viewthread.cfm?qid=97173&page=1 (1141 words)

	VSWR Reduction Calculator (Site not responding. Last check: 2007-10-22)
		To use this calculator to determine the effective VSWR/Return Loss of an attenuator/device combination, enter the attenuation, VSWR or Return Loss, and Gain of the device, then press the ‘Calculate button’.
		An amplifier with a 2:1 Input VSWR and 16 dB gain must be reduced to below 1.5:1.
		A 3 dB Attenuator can be placed before the amplifier to yield an effective VSWR of 1.401 with a gain reduction to 13 dB.
	www.amplifonix.com /vswr.shtml (131 words)

	The KA7OEI FT-817 pages - VSWR metering
		When making these measurements, it immediately became obvious that something was amiss: As you can see, the VSWR indicator showed that with a perfectly good 50 ohm load (I used a known good 50 ohms resistive load rated to 4 GHz) on band 6 meters and up, a "flat" (1:1) VSWR was not indicated.
		This sort of result indicates a misadjustment in the VSWR bridge in the radio, a problem with the design, or a combination of both.
		If the VSWR were bad and the radio didn't reduce its power for some reason some portion of that 5 watt output would be "eaten" by the FT-817, resulting in that much more heat to get rid of.
	www.ussc.com /~turner/ft817_vswr.html (1328 words)

	VSWR Tolerant linear power amplifier - Patent 4547746
		Alternatively, the output from the VSWR tolerant power amplifier 16 could be coupled through a conventional broadband coupling network before being applied to the antenna 18.
		In accordance with the present invention therefore, there is defined a system including the VSWR tolerant power amplifier 16 which enables the supply voltage of the power amplifier to be changed to match changes in impedance.
		Thus, for an increase in the load impedance due to VSWR, the supply voltage is increased and for a decrease in load impedance, the supply voltage is decreased.
	www.freepatentsonline.com /4547746.html (3458 words)

	RWonline - Feed-Line
		The term "VSWR bandwidth" generally is defined as that bandwidth over which the antenna system has a VSWR of 1.1:1 or less (5 percent reflection coefficient).
		VSWR bandwidth generally is measured at the input to the transmission line (or the output of the transmitter).
		In fact, some engineers insist on sideband VSWR of 1.08:1 or less out to 130 kHz either side of the carrier in situations where long transmission lines are employed.
	www.rwonline.com /reference-room/feed-line/07_rwf_feed_line_pt_4.shtml (855 words)

	Antennas for DTV Reception
		In 2002, antenna VSWR and pattern are equally important – if not the most important – specifications.
		The AFCCE concluded that the DTV receiver's noise figure would have to be better than 4 dB when a 7 dB noise figure is used as the basis for determining coverage.
		The effect on the signal-to-noise ratio or error vector magnitude is the same on the receive side as on the transmitter side.
	www.tvtechnology.com /features/On-RF/antennas.shtml (1615 words)

	1. VSWR Monografph and Conversion Chart (Site not responding. Last check: 2007-10-22)
		Typically, a base station antenna system is expected to have a VSWR of 1.5 to 1, or less, measured at the antenna.
		If VSWR is measured at the station end of the transmission line, the indicated VSWR will not be the actual VSWR at the antenna because of attenuation in the transmission line.
		Use of the VSWR Conversion Chart will show that actual VSWR at the antenna is 3.7 to.
	www.guerrilla.net /reference/quick_ref/vswr.html (182 words)

	Antenna & Propagation engineering - some problem about VSWR (HELP!)
		VSWR 1:2.5 means VSWR = 2.5 which is the correct expression.
		VSWR tells how much power will be reflected back to the source.
		The expression 1 : 2.5 as a VSWR is incorrect and might have been intended to be 2.5: 1.
	www.eng-tips.com /viewthread.cfm?qid=57177 (381 words)

	VSWR and magnifiers (Site not responding. Last check: 2007-10-22)
		For a CW system, yes, as VSWR works as the Q of a lumped LC resonator.
		For a capacitor-discharge system, the VSWR works only as a measure of the losses in the resonator (as Q again).
		I don't see physical reasons for any additional voltage gain based on transmission line behavior of the resonator, when compared with lumped LC behavior.
	www.pupman.com /listarchives/1998/April/msg00073.html (132 words)

	VSWR (Site not responding. Last check: 2007-10-22)
		What does happen however is that the meter the ham is using shows that the VSWR goes up as the power is increased.
		However the VSWR is read directly as REFLECTED POWER and the scale assumes you have 10 watts forward power.
		Originally VSWR meters had to have the forward voltage reset each time an adjustment was made.
	jpole.vt11.com /vswrratio.html (508 words)

	IEEE Broadcast Symposium, Part 2
		VSWR (voltage standing wave ratio) –; as well as DTV error vector magnitude monitoring VSWR – is the easiest way to see if the RF system is performing correctly.
		A high VSWR indicates a mismatch somewhere in the transmission line or antenna.
		In one example, a VSWR of 1.3:1 resulted in an amplitude variation of a little more than 2 dB and a group delay variation of 80 ns – resulting in an EVM of more than 11 percent.
	www.tvtechnology.com /features/On-RF/f-dl-ieee2.shtml (1708 words)

	VSWR
		The first consideration for selecting a VSWR meter is that it is designed to operate at the frequency at which you wish to use it.
		It may well show VSWR going up as it goes down, however guaranteed if you tune to the lowest VSWR it will NOT be.
		Although the self adjusting or the fixed level VSWR meters may well give us inaccurate readings the problem is not that the meter is inaccurate but that it is not being used the way it was designed (regardless of the instructions).
	jpole.vt11.com /vswrmeter.html (816 words)

	Standing wave ratio (Site not responding. Last check: 2007-10-22)
		In telecommunication, standing wave ratio (SWR) is the ratio of the amplitude of a partial standing wave at an antinode (maximum) to the amplitude at an adjacent node (minimum).
		For the calculation of VSWR, only the magnitude of ρ, denoted by ρ, is of interest.
		The SWR can also be defined as the ratio of the maximum amplitude of the electric field strength to its minimum amplitude, i.e.
	www.sciencedaily.com /encyclopedia/standing_wave_ratio (754 words)

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