JED - October 2016 - 68


EW 101

Space EW - Part 5

Path Loss from Satellite
By Dave Adamy

T

he total path loss to or from
a satellite includes the lineof-sight loss, atmospheric
loss, antenna misalignment
loss, polarization loss and
rain loss.

Range to Satellite
Elevation
above
Local Horizon
Ground
Station

Height of
Satellite

d

A

90°

RE

LINE-OF-SIGHT LOSS

Local Horizon

B
RE

b

a
D

Center
of Earth

Last month, we calculated the range
Figure 1: The range to any Earth satellite can be calculated from a plane triangle formed by the
to a synchronous satellite, and we calcusatellite, a ground station and the center of the Earth.
lated the loss using the above formula.
Figure 1 shows a more general form of the range calcula100
tion using the plane triangle
formed by the satellite, the
ground station and the center
10
of the Earth. Let's determine
the range from a satellite with
a circular orbit period of two
1
hours to a ground station that
sees the satellite 20 degrees
0.1
above its local horizon - using
the law of sines for plane triTotal (Standard Air)
angles. In Figure 1:
0.01
* Side a is the radius of the
Total (Dry Air)
Earth (6371 km).
Water Vapor
* The angle A is the angle from
0.001
the ground station to the
100
10
200
1
6
20
40 60
2
4
center of the Earth as seen
Frequency (GHz)
from the satellite.
Figure 2: Atmospheric attenuation per km within the atmosphere is a function of frequency and humidity.
Atmospheric Attenuation (dB / km)

The Journal of Electronic Defense | October 2016

68

The primary component of link loss to
or from a satellite is associated with the
extremely long range. Since the satellite
is in space, this loss is the "space loss,"
also called the "line-of-sight" loss, determined from the formula:
L = 32.44 + 20 log(d) + 20 log(F)
Where:
L = the line of sight loss in dB
d = the transmitter to receiver distance
in km
F = the transmission frequency in MHz

Figure 2: Atmospheric attenuation per km within the atmosphere is a function of
frequency and humidity.



Table of Contents for the Digital Edition of JED - October 2016

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
World Report
Bait in the Trap: Trainable Soft-Kill Systems Proliferate for ASMD
2017 EW/SIGINT Resource Guide
SIGINT History
EW 101
AOC News
Index to Advertisers
JED Quick Look
JED - October 2016 - cover1
JED - October 2016 - cover2
JED - October 2016 - 3
JED - October 2016 - 4
JED - October 2016 - 5
JED - October 2016 - The View From Here
JED - October 2016 - 7
JED - October 2016 - Conferences Calendar
JED - October 2016 - 9
JED - October 2016 - Courses Calendar
JED - October 2016 - 11
JED - October 2016 - From the President
JED - October 2016 - 13
JED - October 2016 - 14
JED - October 2016 - The Monitor
JED - October 2016 - insert1
JED - October 2016 - insert2
JED - October 2016 - 16
JED - October 2016 - 17
JED - October 2016 - 18
JED - October 2016 - 19
JED - October 2016 - 20
JED - October 2016 - 21
JED - October 2016 - World Report
JED - October 2016 - 23
JED - October 2016 - Bait in the Trap: Trainable Soft-Kill Systems Proliferate for ASMD
JED - October 2016 - 25
JED - October 2016 - 26
JED - October 2016 - 27
JED - October 2016 - 28
JED - October 2016 - 29
JED - October 2016 - 30
JED - October 2016 - 31
JED - October 2016 - 32
JED - October 2016 - 33
JED - October 2016 - 34
JED - October 2016 - 35
JED - October 2016 - 36
JED - October 2016 - 37
JED - October 2016 - 38
JED - October 2016 - 39
JED - October 2016 - 2017 EW/SIGINT Resource Guide
JED - October 2016 - 41
JED - October 2016 - 42
JED - October 2016 - 43
JED - October 2016 - 44
JED - October 2016 - 45
JED - October 2016 - 46
JED - October 2016 - 47
JED - October 2016 - 48
JED - October 2016 - 49
JED - October 2016 - 50
JED - October 2016 - 51
JED - October 2016 - 52
JED - October 2016 - 53
JED - October 2016 - 54
JED - October 2016 - 55
JED - October 2016 - 56
JED - October 2016 - 57
JED - October 2016 - 58
JED - October 2016 - 59
JED - October 2016 - 60
JED - October 2016 - 61
JED - October 2016 - 62
JED - October 2016 - 63
JED - October 2016 - 64
JED - October 2016 - SIGINT History
JED - October 2016 - 66
JED - October 2016 - 67
JED - October 2016 - EW 101
JED - October 2016 - 69
JED - October 2016 - AOC News
JED - October 2016 - 71
JED - October 2016 - Index to Advertisers
JED - October 2016 - 73
JED - October 2016 - JED Quick Look
JED - October 2016 - cover3
JED - October 2016 - cover4
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