
How a Cray-2 supercomputer was used to decode a movie ham radio transmission - bane
http://swling.com/blog/2016/01/how-bob-mcgwier-used-a-cray-2-supercomputer-to-decode-a-ham-radio-transmission-heard-in-star-trek-iv/
======
zdw
> 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
I was going to post the same thing...

------
jgrahamc
I 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...](http://blog.jgc.org/2011/11/downton-abbey-
series-1-episode-1-morse.html)

------
Animats
Ah, Phil Karn, who had TCP/IP running on ham radio in the early 1980s.

------
wglb
Bob 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-ta...](http://www.arrl.org/news/tom-clark-k3io-
to-speak-at-amsat-tapr-banquet). 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.

~~~
zitterbewegung
Also , the ARRL is one of the organizations that lobby for spectrum to be
publicly available.

------
mmmBacon
As 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).

------
grkvlt
> 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

------
BrainInAJar
but what was the content of the packets?

~~~
employer
RR is Receive Ready in the HAM world, so I suppose he was indicating that he
was ready to receive comms from someone else.

~~~
empthought
It is part of the AX.25 data protocol, not meaningful communication between
humans.

~~~
acqq
Thanks. 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

