JED - June 2015 - 52

a
in radians
r is the radius of the cylinder in meters
F is the signal transmission frequency in MHz

E W101
a = atan[ H/d1] + atan [H/d2]
Now the extra attenuation in addition to the KED and LOS attenuation can be calculated from the formula:
LCYL = 11.7 a

rf
96

2 D d1 d2
Where: LCYL is the additional attenuation above KED and LOS in
dB,
a is the angle between the ray from the transmitter and
a [d1 2 + d2 2]
the ray to the receiver in radians,
r is the radius of the cylinder in meters, and
f is the signal transmission frequency in MHz.

FOR EXAMPLE
Building on the knife-edge diffraction example from last month:
*	 d1 is 20,000 meters,
*		 2 is 28,300 meters,
d
*		 is 62 meters,
H
*		 is 150 MHz, and
F
*		 he	knife	edge	extends	above	the	line-of-sight.
t
We calculated the KED loss to be 10 dB and the LOS loss to be
109.6 dB.
Now, we add the value of 10 meters for D.
Using the above formulas,
a = atan(62/20,000) + atan (62/28,300) = .003 + .0022 = .0052 radians

For Example
Building on the knife edge diffraction example from last month:
* d1 is 20,000 meters
* d2 is 28,300 meters
* H is 62 meters
* F is 150 MHz
* The knife edge extends above the line-of-sight
We calculated the KED loss to be 10 dB and the LOS loss to be 109.6 dB.

r = [2 x 10 x 20,000 x 28300] /[.0052(20,0002 + 28,3002)] =
1.132 x 1010 /6.2 x 106 = 1,826 meters
LCYL = 11.7 x .0052 x sqt[(1826 x 150)/ 96] = 3.2 dB
Now, we add the value of 10 meters for D.
Last month, we calculated the line-of-sight loss (ignorUsing the above formulas,
ing the ridge line) as 109.6 dB and the knife-edge diffracation loss as+ 10 dB. Thus, the total link loss is:
= atan(62/20,000) atan (62/28,300) = .003 + .0022 = .0052 radians
r 109.6 xdB + x10 dB + 3.2 dB+ = 122.8 dBx 10 /6.2 x 10 = 1,826 meters
= [2 x 10 20,000 28300] /[.0052(20,000 28,300 )] = 1.132
2

2

10

6

LCYL = 11.7 x .0052 x sqt[(1826 x 150)/ 96] = 3.2 dB

WHAT IF THERE ARE TREES ON THE RIDGE LINE?

Last month, we calculated the line of sight loss (ignoring the ridge line) as 109.6 dB and the knife edge
diffraction loss as 10 dB Thus, the total link loss is:

If the ridge line is covered by trees (as in the right side
of Figure 3), the cylindrical attenuation is reduced by 65%,
or IF THERE ARE TREES ON THE total link attenuation would be 120.9
WHAT1.9 dB. Thus, theRIDGE LINE?
If the ridge line is covered by trees (as in the right side of Figure 3), the cylindrical attenuation is reduced
dB.
by 65%, or 1.9 dB. Thus, the total link attenuation would be 120.9 dB.
For a bare ridge line, the total loss is:
For a bare ridge line, the total loss is:
109.6 dB + 10 dB + 3.2 dB = 122.8 dB

LLOS + LKED + LCYL

For a wooded ridge line, the total loss is:
LLOS + LKED + LCYL - 1.8 dB

WHAT'S NEXT
Next month, we will discuss another interesting propagation model. For your comments and suggestions, Dave Adamy can be reached at dave@lynxpub.com. a

The Journal of Electronic Defense | June 2015

52

AOC Professional
evelopment Courses
D
Plan now to attend upcoming AOC courses conveniently
located in the Washington, DC area.
 JUNE 23-26

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Instructor: Mr. Dave Adamy

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JED-M0615 AOC Course Ad HP_MKG.indd 1

2015-05-08 3:13 PM


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JED - June 2015

Table of Contents for the Digital Edition of JED - June 2015

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
World Report
Leadership Interview
Missile Warning for Fighter Aircraft
Technology Survey: RWR/ESM Systems
EW 101
2015 AOC Election Guide
AOC News
Index of Advertisers
JED Quick Look
JED - June 2015 - cover1
JED - June 2015 - cover2
JED - June 2015 - 3
JED - June 2015 - 4
JED - June 2015 - 5
JED - June 2015 - The View From Here
JED - June 2015 - 7
JED - June 2015 - Conferences Calendar
JED - June 2015 - 9
JED - June 2015 - Courses Calendar
JED - June 2015 - 11
JED - June 2015 - From the President
JED - June 2015 - 13
JED - June 2015 - 14
JED - June 2015 - The Monitor
JED - June 2015 - 16
JED - June 2015 - 17
JED - June 2015 - 18
JED - June 2015 - 19
JED - June 2015 - World Report
JED - June 2015 - 21
JED - June 2015 - Leadership Interview
JED - June 2015 - 23
JED - June 2015 - 24
JED - June 2015 - 25
JED - June 2015 - Missile Warning for Fighter Aircraft
JED - June 2015 - 27
JED - June 2015 - 28
JED - June 2015 - 29
JED - June 2015 - 30
JED - June 2015 - 31
JED - June 2015 - 32
JED - June 2015 - 33
JED - June 2015 - 34
JED - June 2015 - 35
JED - June 2015 - 36
JED - June 2015 - 37
JED - June 2015 - 38
JED - June 2015 - Technology Survey: RWR/ESM Systems
JED - June 2015 - 40
JED - June 2015 - 41
JED - June 2015 - 42
JED - June 2015 - 43
JED - June 2015 - 44
JED - June 2015 - 45
JED - June 2015 - 46
JED - June 2015 - 47
JED - June 2015 - EW 101
JED - June 2015 - 49
JED - June 2015 - 50
JED - June 2015 - 51
JED - June 2015 - 52
JED - June 2015 - 53
JED - June 2015 - 54
JED - June 2015 - 2015 AOC Election Guide
JED - June 2015 - 56
JED - June 2015 - 57
JED - June 2015 - 58
JED - June 2015 - 59
JED - June 2015 - 60
JED - June 2015 - AOC News
JED - June 2015 - 62
JED - June 2015 - 63
JED - June 2015 - 64
JED - June 2015 - Index of Advertisers
JED - June 2015 - JED Quick Look
JED - June 2015 - cover3
JED - June 2015 - cover4
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