[Scan-DC] Arlington Police Locate Missing Elderly Man UsingLoJack
Andrew Clegg
andrew_w_clegg at hotmail.com
Sat Feb 5 18:45:52 EST 2011
Here is some basic background on how LoJack operates, lifted from a 2008 FCC
document (FCC 08-186).
Note that this is not the same system that locates people. That system uses
the 216 MHz band, as was pointed out by Bill the other day.
In the text below, "SVRS" is the abbreviation for Stolen Vehicle Recovery
System.
Andy
------
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-six 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-five 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.
LoJack's stolen vehicle recovery network operates as follows. LoJack and
the licensed law enforcement agency install in each LoJack-registered
vehicle a vehicle location unit (VLU) that remains dormant until the owner
reports a vehicle theft. Once police receive a stolen vehicle report, 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 particular VLU to begin transmitting
a brief "tracking" message. The base stations transmit activation messages
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 VLU 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. LoJack currently uses an alternative, uplink duty cycle to
facilitate its "Early Warning Detector" (EWD) operations. 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, which contains
a unique reply code. 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.
According to Section 90.20(a)(6), 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 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 (the tracking duty cycle), and to 200
milliseconds every second during periods that a vehicle is being tracked
actively (the active tracking duty cycle). As revised in 2002, the rule
also permits an alternative duty cycle to the tracking duty 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, mobile operations may be conducted with a
duty cycle of 1800 milliseconds every 300 seconds (the uplink duty 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. Finally, the rule requires applicants to perform an analysis for
each base station located within 169 kilometers (105 miles) of a TV Channel
7 transmitter of potential interference to TV Channel 7 viewers.
LoJack is required to migrate its operations from 20 kHz bandwidth to 12.5
kHz by 2019. According to LoJack, it will need to expend significant
resources to redesign its SVRS operations for narrowband use. Specifically,
LoJack indicates that it will need to redesign and redeploy its RF
infrastructure and supporting software. Over a four year period, LoJack
technicians and field engineers will have to travel throughout the country
to install equipment that will upgrade over 11,000 VTUs, 125 base stations,
and 125 uplink receivers. Following this effort, there will still be over
three million wideband VLUs in consumer vehicles that LoJack will service
over a period of ten years. LoJack will need to operate parallel wideband
and narrowband systems during this ten-year transition period to track
existing wideband VLUs that have not been serviced as well as the upgraded
VLUs. LoJack states that the redesign of its network provides an
opportunity to update its technology. Specifically, LoJack plans to
incorporate GPS and cellular technology into its VLUs. LoJack submits that
many of its requested rule changes are necessary due to transitioning the
SVRS frequency (173.075 MHz) from wideband to narrowband operations.
--------------------------------------------------
From: "Andrew Clegg" <w4jecom at w4je.com>
Sent: Saturday, February 05, 2011 1:35 PM
To: "Doug Kitchener" <oldsdoug at hotmail.com>
Cc: <scan-dc at mailman.qth.net>
Subject: Re: [Scan-DC] Arlington Police Locate Missing Elderly Man
UsingLoJack
> There was an FCC Report & Order a couple years back that included a good
> description of how the system worked. I'll see if I can find that again.
>
> Andy
>
> On Feb 5, 2011, at 12:48, Doug Kitchener <oldsdoug at hotmail.com> wrote:
>
>>
>> OK, so I've programmed in the LoJack frequency below, and it's doing
>> something, because at regular periodic intervals I'm getting a squelch
>> break - possibly a data burst, as it sounds similar to the MSP helos'
>> locator beacons.
>>
>> But, what kind of signal / modulation does it use if it spots something?
>> In other woids, what does it sound like? Also, what's the range?
>>
>> Thanks!
>>
>> ----------------------------------------
>>> From: aclegg at nsf.gov
>>> To: Scan-DC at mailman.qth.net
>>> Date: Fri, 4 Feb 2011 11:12:43 -0500
>>> Subject: [Scan-DC] Arlington Police Locate Missing Elderly Man Using
>>> LoJack
>>>
>>> (FYI, LoJack signals use 173.075 MHz. Always cool to have that in your
>>> scan
>>> list, so you know when you're passing a stolen vehicle, missing person,
>>> or
>>> LoJack base station!).
>>>
>>> http://www.arlnow.com/2011/02/03/arlington-police-locate-elderly-man-using-l
>>> ojack/
>>>
>>>
>>> Andy
>>
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