Power Loss at Various SWR readings and Residual Power

SWR (Standing Wave Ratio) affects the power output of your radio. The following table shows the effect of SWR for a transmitter with 100 watts of transmitted power.




SWR Reading% Of LossEff. Radiated PowerPower Output in WattsPower Loss in Watts
1.0:10.0%100.0%100.000.0
1.1:10.2%99.8%99.80.2
1.2:10.8%99.2%99.20.8
1.3:11.7%98.3%98.31.7
1.4:12.8%97.2%97.22.8
1.5:14.0%96.0%964
1.6:15.3%94.7%94.75.3
1.7:16.7%93.3%93.36.7
1.8:18.2%91.8%91.88.2
2.0:111.1%88.9%88.911.1
2.2:114.1%85.9%85.914.1
2.4:117.0%83.0%8317.0
2.6:119.8%80.2%80.219.8
3.0:125.0%75.0%7525
4.0:136.0%64.0%6436
5.0:144.4%55.6%55.644.4
6.0:151.0%49.0%4951
7.0:156.3%43.8%43.856.3
8.0:160.5%39.5.0%39.560.5
9.0:164.0%36.0%3664
10.0:166.9%33.1%33.166.9

To compute your useful output power into the antenna, read your output power, and multiply it by the ERP percentage above, using your SWR reading.




Example: If your transceiver output is 75.0 Watts, and the VSWR is 1.5. From the table above 1.5:1 the radiating efficiency is 96.0% percent. Simply multiply 75.0 Watts by 0.96 (96/100 to decimal). The result is 72.0 Watts.

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