D.7 Distance and time-dependent loss

The loss in the anomalous propagation mechanism dependent on both great-circle distance and percentage time are calculated by first evaluating the following.

Distance adjusted for terrain roughness factor:

km (D.7.1)

Terrain roughness factor:

h_m > 10 m (D.7.2a)

otherwise (D.7.2b)

A term required for the path geometry correction

(D.7.3)

If α < −3.4, set α = −3.4

Path-geometry factor:

(D.7.4)

If m₂ > 1, set m₂ = 1

Time percentage associated with anomalous propagation adjusted for general location and specific properties of the path:

% (D.7.5)

An exponent required for the time-dependent loss:

(D.7.6)

The time-dependent loss:

dB (D.7.7)

D.8 Basic transmission loss associated with ducting

Basic transmission loss associated with anomalous propagation is given by:

dB (D.8.1)

Appendix E

Troposcatter

E.1 Introduction

The following sections give the method for calculating troposcatter basic transmission loss L_bs not exceeded for a given percentage of an average year. The method is based on selecting an appropriate climatic zone.

E.2 Climatic classification

This sub-model is based on the use of climate zones as shown in Fig. E.1 The zone corresponding to the latitude and longitude of the troposcatter common volume, f_cvn and f_cve, should be read from the file “TropoClim.txt”. This file contains integers in the range 0 to 6. Integers 1 to 6 correspond to the climate zones shown in Fig. E.1. Integer 0 represents a sea location for which a special procedure is required.

Figure E.1

Climatic zones

In case the troposcatter common volume lies over the sea, the climates at both the transmitter and receiver locations should be determined. If both terminals have a climate zone corresponding to a land point, the climate zone of the path is given by the smaller value of the transmitter and receiver climate zones. If only one terminal has a climate zone corresponding to a land point, then that climate zone defines the climate zone of the path. If neither terminal has a climate zone corresponding to a land point, the path is assigned a “sea path” climate zone in Table E.1.

Obtain the meteorological and atmospheric structure parameters M and g, respectively, from Table E.1 for the climate zone in question.

The last row of Table E.1 gives the number of the equation used to calculate Y₉₀ in § E.3 below.

TABLE E.1

Meteorological and atmospheric structure parameters

• ⇐ Назад
• -2
• -1
• 0
• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8910
• 11
• 12
• 13
• Далее ⇒