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Info on Mobile Tracking Equipment


NOTICE: TO ALL CONCERNED Certain text files and messages contained on this site deal with activities and devices which would be in violation of various Federal, State, and local laws if actually carried out or constructed. The webmasters of this site do not advocate the breaking of any law. Our text files and message bases are for informational purposes only. We recommend that you contact your local law enforcement officials before undertaking any project based upon any information obtained from this or any other web site. We do not guarantee that any of the information contained on this system is correct, workable, or factual. We are not responsible for, nor do we assume any liability for, damages resulting from the use of any information on this site.

MOBILE TRACKING EQUIPMENT or "Bumper Beepers".....by The Mad Phone-man
------------------------------------------------------------------------------

You remember the little "bug" installed on the bad guys car in the James Bond
flicks that allowed Bond to follow the car from a distance? Well this file is
a tutorial on them.

First, they do exist, I've built my own, but even the best commercial units
intended for law enforcement purposes wont do what the Bond model purports
to do, that is, give a printout on a moving map showing the route driven by
the bug toter.

The basics of the unit are the transmitter, which is about the size of
a pack of cigarettes and is held on via a magnet. And a receiver, using 2
identical antennas, coupled to a center zero meter which gives a heading
towards the transmitter. More on these later.

The receiver/display unit is used by pilots, amateur radio operators, and
law enforcement and security personnel to track the movements of the
transmitter
usually at short ranges, the civil air patrol uses these units to find
downed aircraft by tracking the emergency beacon, activated by the
impact of the crash. Amateurs play "hunt the fox" to keep illegal transmitters
out of the ham bands. Law enforcement personnel track the movement of people,
drugs, and weapons by attaching a transmitter to the object (or suspect's
car) to be followed.

The transmitter is usually a small VHF or UHF battery operated package
dangling a 19" flexible antenna (about the thickness of piano wire). The
transmitter does not "beep" per say, but transmits a continual carrier.
The FBI uses 167.xxx mhz for theirs and the local DA uses the intercounty
police freq of 155.37. I have seen military models that use 149.xxx mhz
around here (air force).

Now the receiver:
Two identical antennas mounted on the chase vehicle (usually magnetic mounts)
feed a pair of PIN diodes that feed a phase detector which samples the
receiver's IF output. When the received signal is directly in front of you,
signals arrive at exactly the same time at each antenna. This is calibrated to
read center 0 on the meter. (Incidentally the unit can't tell if the signal is
in front or in back of you, so the need to make sure you follow the subject
reasonably closely is apparent). If the bug travels say to 10 o'clock on the
compass rose, the needle will swing to 4 o'clock on the meter. The object here
is to always drive towards zero and you follow the bug in the most direct
direction. With a little practice,you can follow a subject on an adjcent
street without loosing him.
The meter swings because the signal arrives later at one antenna than the
other, causing a voltage change in the phase detector (an Exar Radio-teletype
decoder chip in my model).

Some recent units ive seen have Light emitting diodes in a 360 degree circle
and use 4 antennas. This gives you full circle detection capabilitys as the
phase between pairs of antennas is calculated also.

Now, prevention:
The easiest way to detect if you've been planted with one of these little
transmitters, is to walk around the car or whatever with a portable frequency
counter and check for an alien RF signal. This is also the recommended
method to de-bug your home. A small freq counter with 1.2 ghz capabilitys
sells for around $100. today. If you do find a transmitter, have fun with it.
Stick it on a train heading out of town, a Greyhound bus, or a over the road
tractor-trailer rig....my favorite is to stick it on one of their own
vehicles and watch them chase themselves....hehehe.

The Mad Phone-man © 1988

 
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