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 Loss Eff. Radiated Power Power Output in Watts Power Loss in Watts
1.0:1 0.0% 100.0% 100.00 0.0
1.1:1 0.2% 99.8% 99.8 0.2
1.2:1 0.8% 99.2% 99.2 0.8
1.3:1 1.7% 98.3% 98.3 1.7
1.4:1 2.8% 97.2% 97.2 2.8
1.5:1 4.0% 96.0% 96 4
1.6:1 5.3% 94.7% 94.7 5.3
1.7:1 6.7% 93.3% 93.3 6.7
1.8:1 8.2% 91.8% 91.8 8.2
2.0:1 11.1% 88.9% 88.9 11.1
2.2:1 14.1% 85.9% 85.9 14.1
2.4:1 17.0% 83.0% 83 17.0
2.6:1 19.8% 80.2% 80.2 19.8
3.0:1 25.0% 75.0% 75 25
4.0:1 36.0% 64.0% 64 36
5.0:1 44.4% 55.6% 55.6 44.4
6.0:1 51.0% 49.0% 49 51
7.0:1 56.3% 43.8% 43.8 56.3
8.0:1 60.5% 39.5.0% 39.5 60.5
9.0:1 64.0% 36.0% 36 64
10.0:1 66.9% 33.1% 33.1 66.9

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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