JED - September 2016 - 43

TECHNOLOGY SURVEY

A SAMPLING OF MANPACK COMINT AND DF SYSTEMS
By Ollie Holt

T

process repeated. Independent receivers
sharing detection angle information can
also use this process.
For the DF method discussed in Figure 1, the most important element in
the process is the antenna. The antenna
needs to be very directional (i.e., it must
have a very narrow gain pattern in one
direction while having very little performance in any other direction). One
antenna that provides that capability
is a simple multi-element yagi. The yagi
can be used as described in Figure 1, by
rotating it and finding the direction of
highest power. Other antenna concepts
can be used to determine the direction
of highest power. Loop antennas can
be configured similar to the yagi and
electrically or manually rotated. There
are other antenna configurations that
support single-receiver, multi-antenna
DF approaches, such as pseudo-Doppler,
Watson-Watt/Adcock and an interferometry array, which were covered in JED's
June 2016 DF article. These techniques
require the receiver to switch between
different antenna feeds and determine
direction through calculations.

DF TECHNIQUES
If the manportable DF system can
be networked and synchronize GPS location and time with other DF receivers, then both a high-quality DF and
location can be determined by using
techniques, such as Time Difference
of Arrival (TDOA). With time synchronization through the GPS signal, TDOA

Fig. 1: The user collects DF measurements on
an emitter (T) at points A, B and C. The point
where the DF lines of bearing intersect (at
Point T) is the location of the target emitter.

techniques can be incorporated with
amplitude and phase techniques to improve DF and location performance. Even
if the DF systems are not networked, but
if they know their precise location, they
can share angle and position information between systems and plot the data
on a map (similar to what is shown in
Figure 1) to obtain a more precise result.
Each technique has advantages and
disadvantages. Amplitude, using a manually rotated yagi, is relatively simple and
low cost to implement, but it offers only
average performance. The other singlereceiver techniques provide better performance, but with a bit more complexity
in the antenna and antenna feed matrix.
The networked approach using connected
manportable systems can provide very
good performance, but with the added
need for a GPS receiver/antenna system
and some form of communication between systems. Multiple channel receiver
systems can also be implemented using
phased arrays, but they would add weight
and power requirements, which maybe
undesirable in a manportable system.
Some items to note in the survey are;
frequency range, modulation types the
system can detect and process, DF methods, antenna type, battery/operating
time and weight. Operating frequency
range allows the user to determine if the
system covers the frequencies of interest. The modulation types the system can
process allow selection of a system that
can handle signals of interest. The DF
methods help to understand the process
the system uses to determine direction
and some idea of DF performance. The
antenna type also helps in determining
system DF performance. A more complex
antenna configuration may increase
performance. Multiple receiver channels
will provide better performance but with
increased antenna and receiver weight.
Finally both battery type and operating
time before the battery needs recharging
will determine the system's usefulness
for a given COMINT/DF application.
The next survey will be in the December issue of JED and will cover flightline
and portable EW testers and simulators.

The Journal of Electronic Defense | September 2016

his month's survey covers manpack communication intelligence (COMINT)
and direction finding (DF)
systems. The survey covers
complete manpack or portable COMINT/DF systems with receivers
designed to perform signal intercept,
data collection, data analysis, and direction finding (DF) and/or location of
communication emitters in the HF, VHF,
UHF and SHF bands. These systems are
designed to be man portable (i.e. lightweight, battery-operated and compact).
Being compact and lightweight, they
are not expected to have the same performance as some of the more capable
COMINT and DF systems discussed in
the JED's June 2016 article, "Advances
in COMINT/DF Systems," by John Haystead, but they are still able to perform
the functions discussed in his article.
The detection and processing of COMINT signals is rather straightforward
and has been discussed in some of JED's
past surveys and articles. The task of direction finding and location, especially
in a man portable system, is not a simple
process. The easiest method that uses
the smallest amount of hardware is just
a directional antenna rotated by hand to
find the direction of highest signal amplitude (power) either by listening to a
signal or using a signal strength meter.
The direction of highest power, as long
as it is not being reflected off a nearby
building, is the direction from which the
signal is transmitted. This technique
works best in open areas and not so well
in urban areas. If the DF information is
shared between two or more systems,
then a rough idea of transmitter position
can be determined via triangulation.
An example is shown in Figure 1. The
user gets a DF measurement at Point A,
then moves to Point B and makes another measurement. They then draw a line
from Point A in the direction of the DF
measurement and another from Point B in
the direction of the DF measurement. The
place where the lines cross is the target
(T). For better accuracy a third measurement (from Point C) can be made and the

43



JED - September 2016

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

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
World Report
Nothing to See (Or Hear) Here – Concealing Tactical Communications
Technology Survey: Manpack COMINT and DF Systems
The Heat is On
EW 101
AOC News
Index of Advertisers
JED Quick Look
JED - September 2016 - cover1
JED - September 2016 - cover2
JED - September 2016 - 3
JED - September 2016 - 4
JED - September 2016 - 5
JED - September 2016 - The View From Here
JED - September 2016 - 7
JED - September 2016 - insert1
JED - September 2016 - insert2
JED - September 2016 - Conferences Calendar
JED - September 2016 - 9
JED - September 2016 - Courses Calendar
JED - September 2016 - 11
JED - September 2016 - From the President
JED - September 2016 - 13
JED - September 2016 - 14
JED - September 2016 - The Monitor
JED - September 2016 - 16
JED - September 2016 - 17
JED - September 2016 - 18
JED - September 2016 - 19
JED - September 2016 - 20
JED - September 2016 - 21
JED - September 2016 - 22
JED - September 2016 - 23
JED - September 2016 - 24
JED - September 2016 - 25
JED - September 2016 - 26
JED - September 2016 - 27
JED - September 2016 - World Report
JED - September 2016 - 29
JED - September 2016 - 30
JED - September 2016 - 31
JED - September 2016 - 32
JED - September 2016 - 33
JED - September 2016 - Nothing to See (Or Hear) Here – Concealing Tactical Communications
JED - September 2016 - 35
JED - September 2016 - 36
JED - September 2016 - 37
JED - September 2016 - 38
JED - September 2016 - 39
JED - September 2016 - 40
JED - September 2016 - 41
JED - September 2016 - 42
JED - September 2016 - Technology Survey: Manpack COMINT and DF Systems
JED - September 2016 - 44
JED - September 2016 - 45
JED - September 2016 - 46
JED - September 2016 - 47
JED - September 2016 - The Heat is On
JED - September 2016 - 49
JED - September 2016 - 50
JED - September 2016 - 51
JED - September 2016 - EW 101
JED - September 2016 - 53
JED - September 2016 - AOC News
JED - September 2016 - 55
JED - September 2016 - 56
JED - September 2016 - Index of Advertisers
JED - September 2016 - JED Quick Look
JED - September 2016 - cover3
JED - September 2016 - cover4
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