Directional antenna is a gain antenna * Constant O Isotropically Low O High - The power radiated per unit area (watt/m 2) - between the transmitting and the receiving antenna.* increases as the inverse of square range (R*2) decreases as the inverse of square range (R^2) increases as the proportional to the range of power four ( R^4) decreases as the proportional to the range of power four ( R^4) the ratio of signal input to noise ratio (SNR)i to the signal output to noise ratio (SNR)o is known as -- O Noise figure radar cross section reflection coefficient EIRP