What is VSWR?

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What is VSWR?

Postby m0lsx » Wed Oct 03, 2018 5:51 pm

https://www.electronics-notes.com/articles/antennas-propagation/vswr-return-loss/what-is-vswr.php

Standing waves are an important issue when looking at feeders / transmission lines, and the standing wave ratio or more commonly the voltage standing wave ratio, VSWR is as a measurement of the level of standing waves on a feeder.

Standing waves represent power that is not accepted by the load and reflected back along the transmission line or feeder.

Although standing waves and VSWR are very important, often the VSWR theory and calculations can mask a view of what is actually happening.


The terms VSWR and SWR are often seen in the literature about standing waves in RF systems, and many ask about the difference.

SWR: SWR stands for standing wave ratio. It describes the voltage and current standing waves that appear on the line. It is a generic description for both current and voltage standing waves. It is often used in association with meters used to detect the standing wave ratio. Both current and voltage rise and fall by the same proportion for a given mismatch.

VSWR: The VSWR or voltage standing wave ratio applies specifically to the voltage standing waves that are set up on a feeder or transmission line. As it is easier to detect the voltage standing waves, and in many instances voltages are more important in terms of device breakdown, the term VSWR is often used, especially within RF design areas.

The term power standing waves is also seen some times. However this is a complete fallacy as the forward and reflected power are constant (assuming no feeder losses) and the power does not rise and fall in the same way as the voltage and current standing waveforms which are the summation of both forward and reflected elements.


The full article is well worth looking at, using the above link.
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Re: What is VSWR?

Postby m0lsx » Wed Oct 03, 2018 6:00 pm

Anyone got an ISWR or a PSWR meter?
ISWR is a SWR that measures Current & the PSWR measures power.
Many modern SWR meters also show PSWR.
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