Jammer
Some years ago (not that long really) I was using public transport for my (total of 3.5 hours per day) commute.
On occasion there would be someone, where even at the other end of the bus / train carriage, I could hear the loud tinny noises from their earpieces.
Having an excellent relationship with some electronics vendors, I got a set of free samples for 2.5GHz transmitters and a small FPGA board.
The end result was a battery powered transmitter controlled by a simple button, that generated white noise across a several hundred kHz bandwidth into a directional antenna (so I could minimise power usage).
To those who may not know, all that is necessary to demodulate such a signal is a non-linear circuit with an antenna; behold, the audio is on wires and is attached to an amplifier. An antenna with a non-linear circuit!
I have very fond memories of pushing the button and seeing the miscreant with their very loud antisocial 'music' rip the earplugs out and look at their device with disbelief at which point I would release the button to stop transmitting. As soon as they reinserted the earplugs and fired up their 'music' at levels to rival a military aircraft engine, I would press the button again.
Such fun; rather gives 'messing with their head' new meaning.
Biting the hand that feeds IT
