Commonwealth Numbered Regulations

1995 No. 74 RADIOCOMMUNICATIONS (MULTIPOINT DISTRIBUTION STATION LICENCES - REGIONAL LICENCES) GUIDELINES No. 1 of 1995 - SCHEDULE 2

                             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.)