On 02/02/2014 07:30 PM, Tom Metro wrote: > Jerry Feldman wrote: >> 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 >> ...helicopters have 2 different vibration levels, low freq and high >> freq. ... The low freq is caused by the main rotor blades. ... The >> tail rotor is the cause of the high freq. > Interesting, but did you read the article? It wasn't about an analog > sound resulting from a vibration, but instead a digital signal imposed > on the left audio channel, that when decoded turned out to contain the > GPS coordinates of the helicopter. > I did read that, and the aviation radios were probably specialized to filter out and vibration effects. It is interesting that the modem was a Bell 202 ASCII, but previously he said it was a Nucomm Skymaster TX, which was built for aircraft use.
-- 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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