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Cell phones and unlocking cars

  1. Aug 19, 2007 #1
    Has anybody heard of this myth/urban lengend? Any thoughts on how feasible it is?

    This only applies to cars that can be unlocked by that remote button on your key ring. Should you lock your keys in the car and the spare keys are home, and you don't have "OnStar," here's your answer to the problem!

    If someone has access to the spare remote at your home, call them on your cell phone (or borrow one from someone if the cell phone is locked in the car too!)

    Hold your (or anyone's) cell phone about a foot from your car door and have the other person at your home press the unlock button, holding it near the phone.

    Your car will unlock. and it works. Saves someone from having to drive your keys to you. Distance is no object. You could be hundreds of miles away, and if you can reach someone who has the other "remote" for your car, you can unlock the doors (or the trunk, or have the "horn" signal go off, or whatever!) ​

    Everything I think I know about RF, cell phones and antennas (which admittedly isn't very much) says it shouldn't work (like the Snopes article says), but a friend of mine says she tried it with her sister who was 200 miles away and it worked.

    According to the Snopes article, remote keyless entry systems operate at 300 MHz, so the only even slightly plausible explanation I could come up with was that somehow the cell phone's antenna managed to pick up a weak version of the key fob's signal and rebroadcast it through the cell network to the other side where it was received by the car.

    Thoughts? I'm very skeptical about my explanation, but it's the only one I have. I would have thought that cell phones and/or cell phone networks would have filters to weed out interference like this. Maybe someone's trying to pull a fast one on me?
  2. jcsd
  3. Aug 19, 2007 #2


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    It isn't even conceivably possible.

    - Warren
  4. Aug 19, 2007 #3


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    Agreed. I looked this up on snopes.com a couple months ago for a similar thread here on the PF. It's a documented urban legend, which matches what EEs like chroot and I would say based on what we know about how each of those components work.

    I'm too pooped to look up the link again (it's been a long weekend!), but the OP can just go to snopes.com and put in some of the key phrases from his post to get the match.
  5. Aug 20, 2007 #4


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    Sounds to me a bit like the (more entertaining) urban legend that a parrot will mimic the same.
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