SCHEDULE 2 Subclause 3(1) CALCULATION OF PROPAGATION LOSS BETWEEN MDS SERVICES, AND BETWEEN MDS SERVICES AND FIXED LINKS Propagation Loss Components In calculating the propagation loss between MDS services, and between MDS services and fixed links, the basic propagation loss (Lb) between two antennas may be represented by the following components: . a free space basic transmission loss (Lbf); and . an additional component due to the presence of terrain (Lt) ie Lb = Lbf + Lt Initial assessments may be made using the free space transmission loss component only (ie Lt = 0). If, as a result of this assessment, the specified protection requirements are met then the more complex assessment that includes terrain loss is not required. For the purpose of paragraph B.5 (a) of Step 2 in Assessment B, the propagation loss between fixed link transmitters and fixed link receivers should be calculated using only the free space basic transmission loss (Lbf). Free Space Loss The free space loss component (Lbf) is calculated by the following formula: Lbf = 32.44 + 20log(f) + 20 log(d) where: f = frequency (MHz) d = distance (km) Terrain Loss The terrain loss (Lt) may be calculated by using Method A or Method B below. Alternatively, where there is more than one obstacle, ITU Recommendation 526-2 'Propagation by Diffraction' may be used for calculation of terrain loss. (NOTE. ITU Recommendations are available from the Standards Australia International Sales Group, Strathfield NSW.) Method A: Diffraction over a spherical Earth Terrain loss due to diffraction over a spherical Earth is calculated using the formulas below. These formulas are valid for systems operating above 1 GHz and apply to both horizontal and vertical polarisation. Lt = -(F(X) + G(Y1) + G(Y2)) (dB) where: Lt = terrain loss due to diffraction over a smooth sphere (dB) X = the normalised length of the path between the antennas at normalised heights Y1 and Y2 X = 2.2f1/3ae -2/3d Yn = 0.0096f2/3ae-1/3Hn ae = kr (ie, the equivalent Earth's radius (km); see ITU-Rec. 310-8) r = 6370 km (earth radius) k = equivalent earth radius factor (nominally 4/3) Hn = antenna height above the spherical Earth (m) d = path length (km) f = frequency (MHz) (NOTE. ITU Recommendations are available from the Standards Australia International Sales Group, Strathfield NSW.) The distance term is given by : F(X) = 11 + 10log(X) - 17.6X The height gain term is given by: G(Yn) = 17.6(Yn - 1.1)1/2 - 5log(Yn - 1.1) - 8 for Yn > 2 G(Yn) = 20log(Yn + 0.1Yn3) for Yn <- 2 If the equation for Lt gives a value less than zero, the method is invalid, and Lt is to be taken as zero. Method B: Single knife edge diffraction loss calculation Terrain loss due to diffraction over a single knife edge obstacle is calculated using the formulas below. Lt = 6.9 + 20log (((v -0.1)2 + 1)1/2 + v - 0.1) for v > -0.7 where: Lt = terrain loss due to knife edge diffraction (dB) v = Ho(fd/150d1d2)1/2 Ho = height (m) of the top of the obstacle above the straight line joining the two ends of the path d1, d2 = distances (km) of the two ends of the path from the top of the obstruction d = path length (km), f = frequency (GHz) (NOTE: For situations where v <- -0.7 see CCIR Recommendation 526-2. CCIR Recommendations are available from the Standards Australia International Sales Group, Strathfield NSW.)