TELE INTERNATIONAL - TELE-satellite International Magazine

30
or whatever. The other missile, two weeks
before, was a Tomahawk from a ship in the
Adriatic Sea. This was a GPS type. Everyone
should know that jammers were available
all around. Just ask the aviation guys, he
replied.
This made me very curious about what
was going on here. How do normal planes
navigate using this GPS system? I needed a
specialist here. And he was found just right
in my neighbourhood, working for a USAF
supply company. After they scared the hell
out of us with a plane crash, a couple of
months ago, their information policy has
changed to a much more open one.
So I got myself a crash course on GPS.
Secondly, I was told about total dropouts
of the GPS system on planes. Most of the
time, there are three fully independent GPS
systems onboard, and still there have been
cases in which all three malfunctioned. In the
past, it was a British Airways plane in trouble
in France and a couple of months before
that a DC-10 in New York. Apparently,
someone had interfered with the GPS signals,
but there was no talk about terrorists.
The incident in France were caused by the
French Army playing around with a jammer
of 4 watts. They had forgotten to tell the
aviation authorities about it. The case in the
U.S. was the same in fact. Here, the U.S.
Air Force Research Laboratory Information
Directorate (“Rome-Lab”) had forgotten to
warn the FAA.
I learned that GPS was actually developed
for military use only. At the end of the Cold
War, the system was also made available for
civil use, but with less accuracy and depending
on military authorities, meaning they
could turn it off whenever they want. In
total, 21 satellites (plus three for backup) are
circling the globe. The ideal situation for a
GPS receiver would be to receive four satellites.
Three will be used to calculate the time
and distance to the satellites, the fourth for
synchronisation with the atom clock in the
satellite with the GPS receiver. For civil use,
one can get an accuracy of between 15 and
50 meters. One of two GPS-frequencies is
used: 1575.42MHz (L1) but for military use
1227.60MHz is also used. Clever engineers
have developed a method to increase the
accuracy of the civilian GPS. This modified
GPS is in use by an airport in Switzerland
where the runway is rather delicately situated
so that the ILS (Instrument Landing
System) had problems with the topology of
the region. Another use of GPS is truck tracing
for freight forwarders, tracking stolen
Ferraris, and aeroplane and ship navigation.
On the military side, the system is used for
navigation of planes and ships, but also for
missiles.
The Russian counterpart is called
GLONASS. The tests of these jammers in
France and the U.S. were for good reason.
At the Moscow Air Show 98, a GPS/
GLONASS spoofer was introduced which
could interfere with GPS and GLONASS
signals, resulting in putting navigation systems
on the wrong track. Officials always
denied the possibility of this and the name
of this Russian guy was always kept a
secret. But every good journalist will get
himself a copy of the fair catalogue and find
out that it was Dr. Oleg Antonov and his
company Aviaconversiya. The fact that this
Dr Antonov’s GPS jammer
Mr. Antonov and his company are nowhere
registered and very hard to find is a different
story. Civil aviation circles soon began
to question the security of GPS. As the
military tests had proven, the system is by
no means secure.
Surprisingly enough, U.S. company
Mayflower Comm. introduced an Anti-
Jammer system, which is capable of reducing
the range of a jamming transmitter.
Officials in the U.S. called for some conferences
on this subject and there were even
some anti-jamming seminars for engineers.
Could it be that a jamming device had
something to do with the Sofia bombing?
We couldn’t possibly test the military part
of the GPS system, but we must be able
to test this on civilian GPS receiver, right?
I don’t have a GPS receiver, but I do have
a complete building instruction for one. So
the only thing to do was to find all necessary
components.
But this takes a lot of time, and my editor
at TSI started to call me where my articles
were. The deadline for the next TSI issue
was already approaching very rapidly. So
my bosses decided to buy me a complete
GPS receiver with all kinds of extras. An
Army Surplus store supplied us with a pulse
transmitter, to be used as a jammer. And to
prevent interference with more signals than
we actually wanted, we built ourselves a
helical antenna. The GPS receiver was built
into my car and the antenna put up on the
roof with a big magnet.
After the first ride, the display of the GPS
unit showed us perfectly where he had
gone and showed the route as well. You
could even see where we had gone across a
roundabout. The 3D-mode showed everything
from a 3D perspective. A painful detail
was the indication of the speed, which had
been more than was allowed in the country
where we performed our tests.
Enter the jammer, which had to be built
into a second car. It followed the first car
at a distance of 100 meters. We planned
a straight course with a return at the next
roundabout. This way we would get a perfect
course on our display indicating how
to find our way back. The jammer would
be switched on at the roundabout. So after
a three hour ride, we finally reached our
testing area. It’s an area without airports or
Dr. Antonows GPS-Störsender
TELE-satellite International