Mgyver1 said:
I highly recommend Lojack and think it works incredibly well. There's no yearly fee with the basic Lojack but they do have higher end systems with extra features that would have a monthly fee. It is expensive up front but it's a one time purchase and will always be there if you need it.
LoJack operates on 173.015 Mhz.
For the system to function, there must be a LoJack base station (radio transmitter on a tall antenna), police vehicles with a LoJack direction finder, and the LoJack unit in the stolen vehicle.
When you report a car to the police as stolen, the data is entered into the NCIC database. The LoJack base station sees this entry and once a minute, transmits a signal on 173.015 Mhz that activates the LoJack unit in the stolen vehicle. The base station is basically saying "Unit 1234, you're stolen, turn on your radio and begin transmitting!"
Once the unit in the vehicle is activated, it begins transmitting, also on 173.015 Mhz (at a much lower power than the base station), every second.
Any police vehicles with a LoJack direction finder (directional antenna array + head unit with visual indicator) near enough to 'hear' the stolen LoJack signal can see what direction the stolen car is and go find it.
The biggest issue with LoJack is coverage. The nearest covered areas to me are 1.5 hours North (Nashville, TN), 3.5 hrs SE (Atlanta GA), and 4 hrs West (Memphis, TN). So, useless to me.
bloodninja said:
The alternative would be a GPS-based system, but that has its own faults. First and foremost, GPS requires a generally direct line-of-sight to at least a handful of satellites to appropriately triangulate its position.
Another downside to GPS-based systems is a monthly fee since GPS systems will be cell-tower based.