Here is a download of this cheat sheet: VSWR vs. Return Loss

As the electric wave travels through the different parts of the antenna system (receiver, feed line, antenna, free space) it may encounter differences in impedances. At each interface, some fraction of the wave's energy will reflect back to the source, forming a standing wave in the feed line. The ratio of maximum power to minimum power in the wave can be measured and is called the voltage standing wave ratio (VSWR). A VSWR of less than 1.5:1 is ideal, a VSWR of 2:1 is considered to be marginally acceptable in low power applications where power loss is more critical, although a VSWR as high as 6:1 may still be usable with the right equipment.

Just in case you don't care for mathematical equations, here's a little "cheat sheet" table to help understand the correlation of VSWR to the percentage of reflected power that will return.

An article that explains VSWR

This online VSWR Calculator is also very useful

This VSWR calculator will calculate return loss, mismatch loss, loss in percentage and the reflection coefficient. As an added bonus, the results are modifiable and can calculate the other values. In order to improve the VSWR, this calculator also has an extra input for adding an attenuator to improve or reduce the system VSWR. [more...]

VSWR Stands for 'Voltage Standing Wave Ratio' and is used in EMC to specify the effect of a mismatch presented to a test system signal. Here is a brief history and Explanation the term VSWR. [more...]

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