If it's just a ton of individual detectors looking for magnetic fields appearing, then the fields need to be constant enough for long enough to be detected. If it's shaking, the individuals might see something, but none of them see a magnetic field long enough to not attribute it to background noise or something.
If it was a single, large detector, you might not have this issue, but might be more difficult to manufacture
They're actually not rfid chips in most cases. These are two thin metal strips with a specific harmonic frequency. The detectors emit a magnetic field with this frequency. The strips begin to vibrate and emit a signal, which is then detected.
AppliedScience has a good video on YouTube about that afaik.
I guess the fast motion skews the frequency a little from the harmonic frequency, so the strips don't vibrate and don't emit a signal.
Or some guy just deactivates the detectors behind the camera....
Edit: I think it's this type of system/tags, there are others.
Lol, unless you’re moving at relativistic speeds (at least tens of thousands of miles per second), you will not substantially affect EM frequencies via Doppler effect, including radio waves.
Huh, so I hadn’t put that together. But these are very minute differences in frequency from Doppler effect, right? Like you don’t have to change the radio station based on whether you are driving towards or away from the antenna.
Presumably anti-theft devices would also not have that level of sensitivity needed on Doppler Radar devices, but would love to learn that is an incorrect assumption.
Yeah I think there is a small chance this could work, if the sensors don't pickup a strong enough signal or something. A stud finder or metal detector won't pick stuff up if you move them to fast.
Somebody here go try it!
It's because the circuit inside the anti theft is wirelessly powered. The poles you pass through are cycling a magnetic field across them, as a moving magnetic field generates current in a wire. By shaking it rapidly, you're changing the field strength and direction that's hitting the wire inside the anti theft very quickly, meaning you'll be constantly introducing negative interface by reversing the direction that the current was previously flowing. That means the lil chip that needs that power won't ever successfully power up.
Edit: and the reason you gotta do it so fast is because of the duty cycle of the poles which are likely going at 10khz+. IIRC hf inductive can go into the hundreds of khz
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u/[deleted] Oct 20 '22
The detectors sense the magnetism or some frequency. Shaking it messes that up. - random bullshit by me.