Common - LoJack

Links of Interest
Audio recording of Los Angeles Police AIR-8 following a stolen vehicle using LoJack.
Digital Modes Samples - includes an audio sample of a LoJack radio signal.

LoJack antennas on top of police car LoJack antennas on bottom of police copter
LoJack instrument panel inside police copter.

Radio Frequency
Description Frequency Tone
Stolen Vehicle Recovery System (SVRS) 173.0750 CSQ

FCC 90.20(e)(6)

(6) The frequency 173.075 MHz is available for stolen vehicle recovery systems on a shared basis with the Federal Government. Stolen vehicle recovery systems are limited to recovering stolen vehicles and are not authorized for general purpose vehicle tracking or monitoring. Mobile transmitters operating on this frequency are limited to 2.5 watts power output and base transmitters are limited to 300 watts ERP. F1D and F2D emissions may be used within a maximum authorized 20 kHz bandwidth. Transmissions from mobiles shall be limited to 200 milliseconds every 10 seconds, except that when a vehicle is being tracked actively transmissions may be 200 milliseconds every second. Alternatively, transmissions from mobiles shall be limited to 1800 milliseconds every 300 seconds with a maximum of six such messages in any 30 minute period. Transmissions from base stations shall be limited to a total time of one second every minute. Applications for base stations operating on this frequency shall require coordination with the Federal Government. Applicants shall perform an analysis for each base station located within 169 km (105 miles) of a TV Channel 7 transmitter of potential interference to TV Channel 7 viewers. Such stations will be authorized if the applicant has limited the interference contour to fewer than 100 residences or if the applicant:

(i) Shows that the proposed site is the only suitable location;
(ii) Develops a plan to control any interference caused to TV reception from the operations; and
(iii) Agrees to make such adjustments in the TV receivers affected as may be necessary to eliminate interference caused by its operations.

The licensee must eliminate any interference caused by its operation to TV channel 7 reception within 30 days of the time it is notified in writing by the Commission. If this interference is not removed within the 30-day period, operation of the base station must be discontinued. The licensee is expected to help resolve all complaints of interference.

How LoJack Works
by Harry Marnell

The LoJack stolen vehicle recovery system, "SVRS" has two options - the traditional stolen vehicle tracker, and a new "Early Warning Detector," which detects and signals either external movement of a car, or its' being hot-wired. The EWD signal goes to LoJack, and they attempt to notify the vehicle owner that it's possibly being stolen. This option is apparently popular with trucking companies and other fleet operators.

As of 2002, the 2.5 watt mobiles are allowed to transmit a digital signal for up to 200 ms (1/5 of a second) every 10 seconds - all the time, it appears. Once they've been reported stolen and are being "actively tracked," they can transmit a 200ms signal for the police once every second. Optionally, they can now add a 1800 ms uplink cycle when activated - (either "early warning" or reported stolen). They can transmit the 1800ms (1.8 seconds) signal every 5 minutes, with a maximum of six such messages in any 30-minute period. This 1800ms signal is long enough to ID the unit and to let the base know that it has, in fact, received the instruction to transmit its "I'm stolen" signal to police units. Previously, once a vehicle was reported stolen, all the LoJack base stations would transmit a 300-watt "turn yourself on" signal every 15 minutes for the first two hours, and then once an hour for 30 days, or until the vehicle was recovered, whichever occurred first. The 1800ms cycle for the mobiles lets the base stations know "I heard you, I'm turned on, you can shut up now." Apparently they want to reduce the base stations' transmissions as much a possible, to avoid interference with adjacent TV Channel 7.

The LoJack Story: Government Frequencies
by Goldberg, Godles, Wiener & Wright

The LoJack Corporation of Massachusetts ("LoJack") needed a frequency, a standard 25 KHz channel, for its newly-developed stolen vehicle recovery system. The LoJack System consists of a radio transmitter-receiver unit that is hidden in motor vehicles; a tracking device mounted in police vehicles; and a computerized network of radio transmitters by which the law enforcement agencies signal the LoJack Unit to begin transmitting when a LoJack Unit-equipped vehicle is reported stolen. Upon receiving this signal, the unit begins transmitting its unique reply code, and police vehicles with direction-finding receivers within range of the transmitting LoJack Unit are able to track and locate the stolen vehicle.

There were a number of practical and technical constraints on LoJack as to where in the radio spectrum it could find a usable frequency for its system. Given the fact that the basic function is radio-location in heavily built-up urban areas, LoJack could not use a frequency too high in the spectrum because of multipath problems. Also, because LoJack relies on transmissions over a wide area from a low power device small enough to be hidden on a vehicle, the ideal frequency again would have to be fairly low in the radio spectrum -- certainly under 1000 MHz. The final constraint dictating the lower ranges of the spectrum was, as a consumer item, the cost of producing the LoJack unit must be low.

After a, not surprisingly, unsuccessful search for a non-government frequency below 500 MHz, LoJack approached the Federal Bureau of Investigation for assistance in finding a frequency. The FBI staff conducted an informal survey of the federal government's frequencies, and recommended frequency 173.075 MHz as the best choice for LoJack, largely because that frequency borders TV Channel 7 (174 to 180 MHz), which makes traditional federal government land mobile radio uses difficult to accommodate without the danger of interference to Channel 7. As a result, this frequency was not heavily used by the federal government.

In 1984, LoJack and the Massachusetts state police began to use 173.075 MHz to demonstrate the LoJack System. Formal approval was necessary from the federal Interdepartment Radio Advisory Committee (IRAC), administered by the National Telecommunications and Information Administration (NTIA), under the Department of Commerce, which controls all federal government frequencies.

After about a year of technical tests, LoJack had established the efficacy of the system and wanted to see if there was a consumer market for the technology. At this point, the federal government people did not want to be responsible for a market test and suggested that a market test be administered by the FCC. Therefore, on October 18, 1985, LoJack and the Massachusetts state police filed joint applications for an experimental authorization, to include a market test. LoJack's application covered the transmissions from and the marketing of the in-car mobile LoJack units, and the state's application covered the base station transmitters. Anticipating possible broadcaster opposition because of the proximity of the frequency to Channel 7, included with the initial application was an extensive engineering test report showing that there was no significant risk of interference to Channel 7.

Since a government frequency was involved, the FCC's Office of Engineering and Technology ("OET") forwarded the experimental application to NTIA for its approval. In a February 21, 1986 letter, NTIA "agreed in principle" with the proposed use. The NTIA letter went on to suggest that the Commission explore accommodating permanent use on a nongovernmental frequency. Because the OET staff did not want to authorize another market test on delegated authority, the applications had to go to the full Commission. On March 12, 1986, the Commission approved the grant.

Three days after the Public Notice of the grant, the Channel 7 licensee in Boston, WNEV-TV, petitioned for reconsideration of the Commission's order, claiming potential adverse impact from the LoJack System's operation. The Association of Maximum Service Telecasters (AMST), a trade association of TV broadcasters, also petitioned for reconsideration, submitting its own engineering report to support the claim of potential interference. After further pleadings, including late comments by the National Association of Broadcasters (NAB) and various other broadcasters supporting reconsideration, the Commission denied the petitions in October 1986.

Although LoJack had its market test, the test bed was not entirely a bed of roses. The FCC and NTIA are understandably wary of market tests. They expose a new technology or service application to the public without many of the consumer and regulatory safeguards that would apply in regular operation. The government wants to be sure that the public will not be "stuck" with bad products and services and will not bear the risk if the FCC withdraws or does not renew the authorization. Therefore, LoJack had an obligation to give stringent notices, warnings, and caveats to its customers regarding the risks involved in buying the LoJack product. This obviously was a barrier to sales and, therefore, skewed the market test results, and LoJack, to overcome customer resistance, offered a money-back guaranty to all its customers, if the FCC were to withdraw the authorization. LoJack donated the base stations and tracking units to the Massachusetts police, in order to overcome their own resistance to buying products that were subject to such risks.

Another disadvantage to the market test resulted from the government's concern that, once the technology was in the marketplace, the horse was out of the barn and the government's hands would be effectively tied if it decided to pull LoJack back from the public. As a result, although LoJack requested market test authority for a larger area than Massachusetts, the authority that was granted was strictly confined to Massachusetts.

While the FCC mitigated the worst effects of the geographical limitation by granting many special temporary authorizations (STA) to demonstrate the LoJack system for short periods of time outside of Massachusetts, there was a great reluctance to extend the market test outside of Massachusetts. This situation eventually led to LoJack's filing its petition for rulemaking to go operational by obtaining a regular assignment of 173.075 MHz.

Thus, on March 31, 1988, LoJack petitioned the FCC for a notice of proposed rulemaking (NPRM) to allocate frequency 173.075 MHz permanently for stolen vehicle recovery system use across the country, with state and local law enforcement agencies to be the licensees, along with continued use by the federal government. Given both the technical success and consumer acceptance of LoJack, numerous public safety officials from Massachusetts and other states wrote to support the petition. However, in May 1988, the FBI advised that it would not support a permanent authorization of use of 173.075 MHz. Only two broadcaster groups opposed the petition, basically restating the possible Channel 7 interference argument.

The FCC again referred the Petition to NTIA and NTIA in turn consulted IRAC. Despite the FBI's opposition, NTIA advised the FCC that it supported the sharing of 173.075 MHz with state and local law enforcement agencies for purposes of stolen vehicle recovery systems. The FCC issued a proposal for rulemaking on December 12, 1988, and adopted the proposed rules at the end of September 1989 -- five years after the first technical tests were started in Massachusetts.

Special thanks to Harry Marnell for contributing information