Comment 8VC1 Re: I can't say I understand this 100%


Keyless entry fobs result in rash of vehicle thefts


I can't say I understand this 100% (Score: 1)

by on 2015-05-11 16:49 (#8TZY)

Ok, the car sends constantly some kind of 'hello' signal. Usually it has a reach of 30cm. Fine. The amplifier increases signal tremendously... understood. But now the key has to 'answer'. And its signal is not amplifies. So how far away its signal can be detected by the car? And where is the problem to limit this reach to perhaps 1m? Then the thieves you need two amplifier... And a way to get close to the key without the owner noticing it.

Re: I can't say I understand this 100% (Score: 1)

by on 2015-05-11 19:00 (#8V64)

No doubt the signal boosters/amplifiers in question are bi-directional.

There is no way for a radio signal to be limited to any specific range. The typical working distance is based on the common antenna configuration(s). Using a highly directional (high gain) antenna, you can reach a signal from many times further away than it was ever designed for. For example, how many people are stealing distant neighbor's WiFi, thanks to a Pringles cantenna, or similar?

Re: I can't say I understand this 100% (Score: 1)

by on 2015-05-11 20:38 (#8VC1)

Sure, the amplifiers are bi-directional, but even such amplifiers have limits. If the normals distance is 30cm, you go within the 30cm range of the car and maybe amplify it to 100m. No problem. This I understood. But an amplifier can only boost what is receives. How far are key/car usually apart. when the car is parked and the owner at home? 20m? 40m? You say there is no way to limit a radio signal to a specific range. Of course not. But when the strength of the key signal is too weak to be detected by the amplifier in 1m distance, it effectively is limited. So, why is the signal strength of the key so strong, that the amplifier can receive and amplify its answer over such a large distance?

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