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How a Cray-2 supercomputer was used to decode a movie ham radio transmission
- BrainInAJar 11y agobut what was the content of the packets?
- employer 11y agoRR is Receive Ready in the HAM world, so I suppose he was indicating that he was ready to receive comms from someone else.
- empthought 11y agoIt is part of the AX.25 data protocol, not meaningful communication between humans.
- acqq 11y agoThanks. It can be seen here, it's just 8 bits, highest three are there called NR, so they were 011, lowest 4 were 0001 which means RR receive ready. https://www.tapr.org/pub_ax25.html https://www.tapr.org/pub_ax25.html Fig. 7 -- S frame control fields
- jlgaddis 11y agoReceive Ready for block number three.
- Animats 11y agoAh, Phil Karn, who had TCP/IP running on ham radio in the early 1980s.
- jgrahamc 11y agoI like stuff like this. Watching Downton Abbey I wondered what the CW was at the start of the first episode: http://blog.jgc.org/2011/11/downton-abbey-series-1-episode-1-morse.html http://blog.jgc.org/2011/11/downton-abbey-series-1-episode-1...
- zdw 11y ago> P.S. A Cray-2 is about 50% faster than the fastest Pentium-Pro computer available today. Again, keep in mind that the message above dates from 1989! I'm thinking the dates on this are off a bit, as the Pentium Pro came out in 1995: https://en.wikipedia.org/wiki/Pentium_Pro https://en.wikipedia.org/wiki/Pentium_Pro The first PC I ever built was in 1997, and had a dual socket Pentium Pro logic board which was great for Linux, not so great for non-NT Windows.
- jolux 11y agoI was going to post the same thing...
- mmmBacon 11y agoAs a note on how computing power has improved since 1989, we can now remove impairments and decode optical nPSK at 32Gbd/s ~155k Symbols (2-4 bits per symbol in 2 polarizations) in about 8s using offline processing (data captured from a device like high sample rate sampling scope).
- wglb 11y agoBob McGwier is an interesting fellow. I met him at Dayton many years back when TAPR was just getting into DSP devices: http://www.arrl.org/news/tom-clark-k3io-to-speak-at-amsat-tapr-banquet http://www.arrl.org/news/tom-clark-k3io-to-speak-at-amsat-ta.... I think he was doing work for a defense research outfit at the time. Getting way off the topic, some of the events at Dayton are quite interesting. At one dinner, I got to hear Joe Taylor https://en.wikipedia.org/wiki/Joseph_Hooton_Taylor,_Jr https://en.wikipedia.org/wiki/Joseph_Hooton_Taylor,_Jr speak about his work on pulsars. He brought some audio clips of pulsars, the first gave a "click" about once a second. The second clip was at ten per second, and the final one produced a tone of 600 clicks per second. He credits his interest in physics (along with his brother) to amateur radio as a young boy.
- deleted 11y ago[deleted]
- zitterbewegung 11y agoAlso , the ARRL is one of the organizations that lobby for spectrum to be publicly available.
- grkvlt 11y ago> A few years later when half the bad guys in the world seemed to be using AX.25 and cheap ham gear Also, note that this awesome research was paid for by the NSA via their sponsorship of the lab and Cray machine. I assume because FSK decoding is useful for SIGINT... EDIT: see quote above