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What is meant by the VSWR of an antenna?

The Voltage Standing Wave Ratio (VSWR) is an indication of the amount of mismatch between an antenna and the feed line connecting to it. The range of values for VSWR is from 1 to ∞. A VSWR value under 2 is considered suitable for most antenna applications. The antenna can be described as having a good match. So when someone says that the antenna is poorly matched, very often it means that the VSWR value exceeds 2 for a frequency of interest. Return loss is another specification of interest and is covered in more detail in the Antenna Theory section. A commonly required conversion is between return loss and VSWR, and some values are tabulated below, along with a graph of these values for quick reference.

Return loss (dB)

Return loss (Absolute Value)

VSWR

0

1

26.848

0.0454

1.1

20.827

0.0909

1.2

15.563

0.1667

1.4

12.736

0.2307

1.6

10.881

0.2857

1.8

9.542

0.3333

2

6.020

0.5000

3

4.436

0.6000

4

3.521

0.6667

5

1.743

0.8181

10

0.8693

0.9047

20

0.3474

0.9607

50

0.1737

0.9801

100

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1140 W. Thorndale Ave.
Itasca, IL 60143, USA
Tel: (+1) 847 671 6690
Tel: (+1) 800 648 2800
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