Most helicopters used by news organizations are turboshaft. Only the smallest helicopters these days use piston engines. The turboshaft would emit a constant. But.... helicopters have 2 different vibration levels, low freq and high freq. These vibrations are why a helicopter's main mission in life is self destruction. The low freq is caused by the main rotor blades. Depending on whether they are semi-rigit or fully articulated, each blade has its own independent angle of attack,. and angle between the blades an plane of rotation. The tail rotor is the cause of the high freq. I have seen helicopters go into vibration on the ground and destroy themselves.
On 02/02/2014 02:11 AM, Tom Metro wrote: > A self-taught signals & electronics hacker from Helsinki spotted a > curious pattern in an audio recording of a helicopter and figured out > how to decode it...and what it meant. > > > Mystery signal from a helicopter > http://www.windytan.com/2014/02/mystery-signal-from-helicopter.html > > Last night, YouTube suggested a video for me. It was a raw clip from a > news helicopter filming a police chase in Kansas City, Missouri. I > quickly noticed a weird interference in the audio, especially the left > channel, and thought it must be caused by the chopper's engine. I > turned up the volume and realized it's not interference at all, but a > mysterious digital signal! And off we went again. > > > -Tom > _______________________________________________ > Hardwarehacking mailing list > [email protected] > http://lists.blu.org/mailman/listinfo/hardwarehacking > > -- Jerry Feldman <[email protected]> Boston Linux and Unix PGP key id:3BC1EB90 PGP Key fingerprint: 49E2 C52A FC5A A31F 8D66 C0AF 7CEA 30FC 3BC1 EB90
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