For Electronic Counter Measures (ECM), this app is used to determine the jammer-to-signal (J/S) ratio. For a tracking radar, enter the power in kW, antenna gain in dB, and IF bandwidth in MHz. Then enter the aircraft cross sectional area in m^2 and the range in km, for a self-screening jammer on board with transmitter power in kW over a bandwidth in MHz and given antenna gain in dB at a distance from the radar in km

For example, Enter Pt = 100, Gr = 35, Br = 1, A = 4, R = 3, Pj = 1, Bj = 20 and Gj = 10. Your values for J/S (SSJ) should be 16.5.