[Scan-DC] More info on LoJack at 173.075 MHz

[Andrew Clegg]

Guys,

Thanks to all of you for your input on LoJack. I came across the following
succinct discussion of how LoJack works (from an FCC Notice of Proposed Rule
Making that would require LoJack to narrowband its operations by 2009,
document FCC 06-107). Also, if you query 173.075 MHz in the ULS, you can
retrieve the coordinates of the local LoJack base stations that John Wilson
referred to in a previous post.

Cheers,
Andy

*****
2.	In 1989, the Commission designated frequency 173.075 MHz for use by SVRS
licensees  on a shared basis with the Federal Government.   LoJack has
developed and operates a stolen vehicle recovery network in cooperation with
state and local police departments across the Nation.   According to LoJack,
its system has been deployed in twenty-two states and the District of
Columbia, has been installed in more than three million vehicles, and has
assisted in the recovery of more than 100,000 vehicles.   The LoJack system
also is used in twenty-four other countries.   Although the Commission
licenses SVRS operations on frequency 173.075 MHz on a shared, non-exclusive
basis, LoJack currently is the only SVRS operator in the United States.

3.	Vehicles are fitted with a vehicle location unit (VLU) that remains
dormant until an owner reports a vehicle theft.    Once a stolen vehicle
report is received by police, the officials send an electronic message to a
central law enforcement computer, which causes a network of radio base
stations licensed to the police to broadcast a message that instructs the
VLU to begin transmitting a brief “tracking” message.   Activation messages
are transmitted by these base stations every fifteen minutes for the first
two hours, then once an hour thereafter until the vehicle is recovered or
thirty days have passed, whichever is sooner.   The tracking message
contains a unique reply code that is received by vehicle tracking units
(VTUs) located in law enforcement vehicles.  Police identify the vehicle
make, model and registration from the reply code, and then use that
information to track and recover the stolen vehicle.

4.	Section 90.20(e)(6) of the Commission’s Rules establishes the
requirements for SVRS operations.  SVRS systems may be operated only to
recover stolen vehicles and not for any other purpose.  The rule limits
mobile transmitters to 2.5 watts power output, and base station transmitters
to 300 watts effective radiated power (ERP).  Base station transmissions are
limited to a total of one second every minute.  Transmissions from mobile
units are routinely limited to 200 milliseconds every ten seconds, and to
200 milliseconds every second during periods that a vehicle is being tracked
actively (the 200 milliseconds cycle).  As revised in 2002, Section
90.20(e)(6) of the Commission's Rules also permits an alternative duty cycle
to the 200 milliseconds cycle, which enables SVRS operations to incorporate
an early warning feature that minimizes lag time and, thus, assists in the
expeditious recovery of a stolen vehicle.  Specifically, VLU operations may
be conducted with a duty cycle of 1800 milliseconds every 300 seconds (the
1800 milliseconds cycle) with a maximum of six messages in any thirty-minute
period.  Transmissions from base stations must be limited to a total time of
one second every minute.  LoJack currently utilizes the 1800 milliseconds
cycle to facilitate operation of its “Early Warning Detector” (EWD).   When
activated, the EWD detects external movements of the vehicle or determines
that the vehicle has been started without use of a key and, thereupon,
instructs the VLU to begin transmitting a brief periodic tracking message.
The tracking message contains a unique reply code, which is nearly
instantaneously received by the VTUs installed in law enforcement vehicles.
The nearest base station processes and forwards the message to the LoJack
central control center, whereupon LoJack personnel immediately alert the car
owner that the vehicle is possibly being stolen.