Thread: Unlock your car with a tennis ball?
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Old Aug 9, 2007 | 08:11 PM
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sparks81
Joined: Jul 2007
Posts: 94
Likes: 1
From: Peoria, AZ.
Default Re: Unlock your car with a tennis ball?
Ok, I'm calling this one a hoax. Big time hoax.

I am an electronic engineer, plus I'm the sales manager for a company that sells radio based automation systems. I know radio, I live it every day at work.

First lets begin with the key fob. Per the manual:

This transmitter complies with FCC rules part 15. Operation
is subject to the following conditions:
1. This device may not cause harmful interference.
2. This device must accept any interference that may be
received, including interference that may cause undesired
operation.

Ok, lets explain. The fob is an RF device. RF meaning radio frequency. These are the frequencies we use for our radios, TV's, R/C cars, phones, etc. Everything wireless that is NOT infrared.

The FCC rules part 15 governs the frequencies that are not licensed. See above reference for most of those types of devices. These devices are typically very low power which is why the effective distance is measured in feet. And as such, cannot cause interference and must accept interference by the licensed FCC transmitters such as a mobile radio or radio station, etc.

Point #2. Your cell phone is an analog to digital device. It translates the audio (your voice or noise) into a digital signal (RF). This is done through transducers (devices that convert one form of energy into another - a cell phone mic and speaker in this example).

There is no way, let me repeat, no way to convert the radio waves that transmit in MHz (millions of cycles per second - AC power is 60 cycles btw) through the cell phone mic (typically radio for audio frequencies that are much, much lower than RF, typically in the 300Hz to 10KHz range), through the cell phone towers, to another cell phone, out through the speaker (again rated for audio frequencies) to your keyless entry system.

Your voice is analog (audio frequency). Its a sound wave. The cell phone converts this to digital (1's and 0's). The other cell phone converts the 1's and 0's to a sound wave. It cannot retransmit an RF (non-audio) device.

BUSTED!!!
 
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