The Threshold Intensity for a Receiver $\mathrm { I } _ { \mathrm { r } } = 2.5 \times 10 ^ { - 6 } \mathrm {~W} / \mathrm { m } ^ { 2 }$

Essay

The threshold intensity for a receiver $\mathrm { I } _ { \mathrm { r } } = 2.5 \times 10 ^ { - 6 } \mathrm {~W} / \mathrm { m } ^ { 2 }$ If the intensity produced by an antenna equals $10 \mathrm {~W} / \mathrm { m } ^ { 2 }$ at a range of 1 m, the maximum reliable range of the system equals ____ km.