36 lines
1.5 KiB
Plaintext
36 lines
1.5 KiB
Plaintext
= SWR =
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Standing Wave Radio (SWR) is a phenomenon where power sent down a feed line is
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reflected back by the antenna. Due to this, a standing wave is formed in the
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feed line.
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This only occours when the impedance of the antenna and the feed line do not
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match. This is often caused by having the incorrect sized antenna for the
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signal.
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SWR is the same as the ratio of antenna-to-feed or feedline-to-antenna
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impedances, whichever is greater than 1. No reflected power is a ratio of 1,
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and means that there is no interference pattern. Because [[Impedance]] changes with
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frequency, the SWR also changes with frequency.
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Becuase of higher SWR means more reflected energy, a lower SWR means more of
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the transmitters power actually makes it out through the antenna as a radio
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wave. The power feeding back to the transmitter also creates interference with
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the signal itself, which can cause voltages higher than what the transmitter is
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designed for. Due to this *most equipment can only handle SWR of 2:1*.
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If you expereince SWR, check
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* Antenna length vs frequency
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* Faulty feed lines/feed line connectors
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* Erratic SWR means loose connections in feed line
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== Meters ==
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An SWR meter allows you to measure the power flowing to and from the antenna,
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therefore calculating the amount of SWR. Another type of SWR meter is a
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directional Wattmeter, determining the amount of power in each direction.
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Antenna tuners exist, which alter the Impedance of the feed line to match that
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of the antenna, so make the SWR 1:1. This is either manual or automatic.
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