JED - August 2014 - 34

WHAT THIS MEANS FOR HF SIGINT
SIGINT is tough enough at higher
frequencies, but HF makes it a potential
nightmare when attempting to combat
technically knowledgeable non-state adversaries who can move from frequency
to frequency and change modulation
from CW to AM, single sideband, FM, FSK
and others, all using a single commercially-available radio costing less than
$1,000 and relatively modest directional
antennas, assuming propagation conditions are "right."
While a directional antenna at HF
would be highly desirable for such purposes, it is not a necessity, as communication over vast distances is often
possible with electrically-short antennas and radiated RF power levels of only
a few watts. A simple wire antenna,
such as a dipole, can be camouflaged
by stringing it through trees or even by
mounting it inside a roof. While hardly
ideal, it can still get the job done, especially at peaks in the sunspot cycle
when long-range propagation is possible
at higher HF frequencies with less power
and a crude antenna.

AN/FLR-9 at Misawa Air Base in Japan that was removed in 2013. (DOD photo)

Using this equipment, two adversaries could, for example, arrange to
send short bursts of high-speed data
at about 3.5 MHz on Monday, 7 MHz
on Wednesday, 25 MHz on Friday, etc.,
using different modulation schemes

The Journal of Electronic Defense | August 2014

34

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each time and randomly changing the
schedule and modulation technique
randomly, leaving the world's SIGINT
systems racing to follow their trail.
The fact that these parties can, depending on frequency and conditions,
be at two distant points on the globe
dramatically worsens the chances of
detecting them.
The most likely way they may be defeated is by the characteristics of HF
propagation itself, as there is no guarantee that Monday's 10 a.m. communication at 3.5 MHz will be possible on the
following Monday - or any other day
- as changes in propagation can defeat
the most persistent operator. If they
fail on multiple attempts at the same
frequency, they may be detected and
become "signals of interest" if they are
not identifiable by databases of known
licensed transmitters whose operation is
known and predictable.
Various methods, most dating back
half a century or more and today highly advanced, are available to triangulate them and track them down to a
comparatively small area where their
position may be easier to locate. In
comparison, if the scheduled communication was to take place at VHF or
UHF frequencies it would be far easier
to detect and locate as propagation
distance is tiny fraction of what can
be achieved at HF. a


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JED - August 2014

Table of Contents for the Digital Edition of JED - August 2014

The View From Here
Conferences Calendar
Courses Calendar
From the President
Letters
The Monitor
Washington Report
World Report
Back to the Future With HF SIGIHT
HF SIGIHT Battles the Ionosphere
Technology Survey: Solid-State Power Amplifiers
Book Reviews
EW 101
Index of Advertisers
JED Quick Look
JED - August 2014 - cover1
JED - August 2014 - cover2
JED - August 2014 - 3
JED - August 2014 - 4
JED - August 2014 - 5
JED - August 2014 - The View From Here
JED - August 2014 - 7
JED - August 2014 - Conferences Calendar
JED - August 2014 - 9
JED - August 2014 - Courses Calendar
JED - August 2014 - 11
JED - August 2014 - From the President
JED - August 2014 - 13
JED - August 2014 - Letters
JED - August 2014 - The Monitor
JED - August 2014 - 16
JED - August 2014 - 17
JED - August 2014 - 18
JED - August 2014 - 19
JED - August 2014 - 20
JED - August 2014 - 21
JED - August 2014 - Washington Report
JED - August 2014 - 23
JED - August 2014 - World Report
JED - August 2014 - 25
JED - August 2014 - 26
JED - August 2014 - 27
JED - August 2014 - Back to the Future With HF SIGIHT
JED - August 2014 - 29
JED - August 2014 - 30
JED - August 2014 - 31
JED - August 2014 - HF SIGIHT Battles the Ionosphere
JED - August 2014 - 33
JED - August 2014 - 34
JED - August 2014 - 35
JED - August 2014 - 36
JED - August 2014 - Technology Survey: Solid-State Power Amplifiers
JED - August 2014 - 38
JED - August 2014 - 39
JED - August 2014 - 40
JED - August 2014 - 41
JED - August 2014 - 42
JED - August 2014 - 43
JED - August 2014 - 44
JED - August 2014 - Book Reviews
JED - August 2014 - EW 101
JED - August 2014 - 47
JED - August 2014 - 48
JED - August 2014 - Index of Advertisers
JED - August 2014 - JED Quick Look
JED - August 2014 - cover3
JED - August 2014 - cover4
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