Standing Wave Ratio And Reflected Power

What is reflected power?

  Reflected power is tells how much power is reflected back to transmitter from the antenna that is caused by an antenna impedance mismatch that is measured in watts. When the high reflected power occurs, the reflect power is absorbed by the transmission line and transmitter that would have a high risk of damaging the transmitter due to antenna system mismatch. So the higher the reflected power, the more of the impedance mismatch between antenna and transmitter, and less forward power feeding to the antenna; and the lower the reflected power, and the more of the impedance match between antenna and transmitter, and more forward power feeding to the antenna.

What is standing wave ratio aka VSWR or SWR?

  VSWR or SWR is a unit of measurement in how much of a match between the antenna and transmitter. So the higher the SWR, the more of the impedance mismatch between antenna and transmitter; and the lower the SWR,  the more of the impedance match between antenna and transmitter. So high SWR has high reflected power, and less forward power feeding to the antenna; and low SWR has low reflected power, and more forward power feeding to the antenna.

What is Impedance?

  Impedance is the total opposition of AC current that is measure in ohms.

 

VSWR to Reflected Power
Quick Reference Conversion Chart

VSWR

Reflected Power Percentage
Of The Forward Power
in %

VSWR

Reflected Power Percentage
Of The Forward Power
in %

1:1 0% 1.3:1 1.7%
1.01:1 0.002% 1.4:1 2.7%
1.02:1 0.010% 1.5:1 4%
1.03:1 0.022% 1.6:1 5.3%
1.04:1 0.038% 1.7:1 6.7%
1.05:1 0.059% 1.8:1 8.2%
1.06:1 0.084% 1.9:1 9.6%
1.07:1 0.11% 2.0:1 11%
1.08:1 0.15% 2.1:1 12.6%
1.09:1 0.19% 2.2:1 14%
1.1:1 0.23% 2.3:1 15.5%
1.11:1 0.27% 2.4:1 17%
1.12:1 0.32% 2.5:1 18.4%
1.13:1 0.37% 2.6:1 19.7%
1.14:1 0.43% 2.7:1 21%
1.15:1 0.49% 2.8:1 22%
1.16:1 0.55% 2.9:1 24%
1.17:1 0.61% 3.0:1 25%
1.18:1 0.68% 4.0:1 36%
1.19:1 0.75% 5.0:1 44%
1.2:1 0.83% 6.0:1 51%
1.21:1 0.90% 7.0:1 56%
1.22:1 0.98% 8.0:1 60%
1.23:1 1.06% 9.0:1 64%
1.24:1 1.15% 10:1 67%
1.25:1 1.23% 20:1 82%
1.26:1 1.32% 30:1 87.5%
1.27:1 1.41% 40:1 90%
1.28:1 1.5% 50:1 92%
1.29:1 1.6% :1 100%
 
 

  = Excellent Antenna Match

 
 

  = Good Antenna Match

 
 

  = Marginal Antenna Match

 
 

  = Antenna Mismatch*

 

*Do not transmit when there is any antenna mismatch, or anything over 25% reflected power.

Related Links:

How To Use A SWR / Wattmeter
Click Here

Conversion Formulas For
SWR and Reflected Power
Click Here

About Transmission Lines
Click Here

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