Oona Räsänen
windytan.com · Personal blog · on HN since 2013
Oona Räsänen writes about signal processing and radio, decoding odd signals, audio and images, and hardware hacks such as pagers and dialup sounds.
What HN saysHN commenters recommend it as a blog they read every post of, praising her signal-related hacking, graphics and entertaining writing.
114HN people shared it
63linked it in comments
79stories submitted
4.6Kstory points
8 months agolast shared
2013people per year2026
Most-shared posts
- 1The sound of the dialup, pictured (2012)22 people · 1.1K points · first shared 2013 · 103 comments on HN
- 2Mystery signal from a helicopter16 people · 1.1K points · first shared 2014 · 78 comments on HN
- 3Homepage15 people · first shared 2014
- 4Decoding radio-controlled bus stop displays (2013)9 people · 89 points · first shared 2013 · 12 comments on HN
- 5Speech to Birdsong Conversion7 people · 146 points · first shared 2021 · 27 comments on HN
- 6The sound of dialup – pictured6 people · 3 points · first shared 2015 · discussion on HN
- 7Smoother sailing: Studying audio imperfections in Steamboat Willie4 people · 191 points · first shared 2024 · 50 comments on HN
- 8Plotting patterns in music with a fantasy record player4 people · 158 points · first shared 2020 · 18 comments on HN
- 9Pea whistle steganography4 people · 45 points · first shared 2015 · 3 comments on HN
- 10Gramophone audio from photograph, revisited4 people · 10 points · first shared 2017 · discussion on HN
- 11Using HDMI EMI for fast wireless data transfer4 people · 10 points · first shared 2023 · discussion on HN
- 12CTCSS fingerprinting: a method for transmitter identification4 people · 8 points · first shared 2016 · discussion on HN
- 13Hacking The Burger Pager4 people · 7 points · first shared 2013 · discussion on HN
- 14Headerless Train Announcements3 people · 130 points · first shared 2014 · 8 comments on HN
- 15A determined 'hacker' decrypts RDS-TMC (2013)3 people · 48 points · first shared 2014 · 5 comments on HN
What HN people wrote when they linked it
monoideism · 2021-05-27
A few of mine:
- https://www.windytan.com/ (windytan: signal processing)
- https://www.righto.com/ (Ken Sheriff: IC reverse engineering, vintage computing, misc)
- https://jvns.ca/ (Julie Evans: software development, particularly networking)
And even though it's not a written blog, a special mention goes to Ben Eater's website, which links to his fantastic YouTube series on building an 8-bit CPU from logic chips, and on building a 6502 computer.
- https://eater.net/
sixothree · 2020-04-29
Prints are available (at least they were). And her blog is definitely worth checking out.
http://www.windytan.com/
(see tab 'infographics')
icebraining · 2020-01-01
Two tech blogs of which I read every post:
http://www.windytan.com/ - Oona Räisänen - great hacker of signal-related stuff (audio, video, wireless, etc), graphics, and more.
https://syonyk.blogspot.com/ - a lot of hacking around batteries, off-grid energy, and teardowns and repairs of various devices.
Non-tech related, Ken White at https://www.popehat.com/ can be quite funny, though he hasn't been posting as much lately.
acdanger · 2014-08-15
Reminds me of the always entertaining blog of Oona Räisänen: http://www.windytan.com/ (she very well might recommend this book somewhere on her site).
It's amazing what one can hear if one spends the effort to truly listen.
davepeck · 2025-01-06
I always enjoy reading Maggie Appleton's blog posts: https://maggieappleton.com
And I always learn from the very deep signal processing fun on Absorptions: https://www.windytan.com
matthberg · 2024-10-27
I found on her website [1] that she released a RDS decoder tool [2] relatively recently (compared to the 2013 of the video at least). Looks like it works with a USB RTL-SDR [3] receiver or a pre-recorded file in a number of formats.
[1]: https://www.windytan.com
[2]: https://github.com/windytan/redsea
[3]: https://www.rtl-sdr.com/about-rtl-sdr
jcims · 2021-10-30
One of the best breakdowns of those sounds i’ve ever seen
http://www.windytan.com/2012/11/the-sound-of-dialup-pictured.html?m=1
watersb · 2021-04-01
Another awesome post from windytan.com -- I still love the deep dive on dialup modem signals (listed as a "Popular Post" on the sidebar there).
http://www.windytan.com/2012/11/the-sound-of-dialup-pictured.html
DEADBEEFC0FFEE · 2020-11-23
You will enjoy this classic.
It's a lovely image showing the dialup handshake . My first modem was a Hayes 1200 baud. Every modem after seemed to double. The protocols got better too. Bidirectional transfers, wow.
http://www.windytan.com/2012/11/the-sound-of-dialup-pictured.html?m=1
gus_massa · 2020-11-22
You may like this classic HN post "The sound of the dialup, pictured" http://www.windytan.com/2012/11/the-sound-of-dialup-pictured.html (HN discussions https://news.ycombinator.com/item?id=15635144 (675 points | Nov 6, 2017 | 108 comments) and https://news.ycombinator.com/item?id=9171514 (174 points | on Mar 9, 2015 | 35 comments))
flyinghamster · 2020-08-28
I have a couple of NESDR Smart dongles from NooElec [1], that have worked very well for me. I run them on a Raspberry Pi 3 and pipe audio output to my desktop or laptop with PulseAudio.
Aside from SDR# on Windows and gqrx on Linux, there's also GNU Radio [2] and a variety of lightweight applications that can run on, let's say, a Raspberry Pi Zero [3]. Oona Räisänen has a fascinating blog that touches on digital signal processing as well, applicable to SDRs as well.
Me? No ham license, but that may come someday.
[1] https://www.nooelec.com/store/
[2] https://www.gnuradio.org/
[3] https://osmocom.org/projects/rtl-sdr/wiki/Rtl-sdr
[4] https://www.windytan.com/
hestipod · 2019-07-31
Related older pieces from a brilliant Finnish hacker. Her posts are always interesting:
https://www.windytan.com/2014/06/headerless-train-announcements.html
https://www.windytan.com/2013/11/decoding-radio-controlled-bus-stop.ht…
danparsonson · 2017-11-06
Classic article! I would also like to recommend http://www.windytan.com/2014/02/mystery-signal-from-helicopter.html - Oona is clearly a talented engineer :-)
sillysaurus3 · 2017-11-06
BTW, every post from this blog is amazing. See the two recent ones:
http://www.windytan.com/2017/09/descrambling-split-band-voice-inversio… "Voice inversion is a primitive method of rendering speech unintelligible to prevent eavesdropping of radio or telephone calls."
http://www.windytan.com/2017/07/virtual-music-box.html "A little music project I was writing required a melody be played on a music box. However, the paper-programmable music box I had (pictured) could only play notes on the C major scale. I couldn't easily find a realistic-sounding synthesizer version. [...] Perhaps, if I digitized the sound myself, I could build a flexible virtual instrument to generate just the perfect sample for the piece!"
My favorite is "Mystery signal from a helicopter" http://www.windytan.com/2014/02/mystery-signal-from-helicopter.html
fapjacks · 2017-09-02
I say every time I see one of these HN posts: Windytan, phenomenal hardware hacker: https://www.windytan.com
bitcrusher · 2017-07-17
Meta Note: If you don't read Oona's blog regularly, you're really missing out on some great stuff. Even if you have little interest in sound processing, her discovery processes are more than worth the price of admission.
Here is just one great example of many:
http://www.windytan.com/2013/11/decoding-radio-controlled-bus-stop.htm…
makmanalp · 2016-10-27
On the more technical side, some that blow my mind:
Windytan: http://www.windytan.com/
DJ Bernstein: https://cr.yp.to/djb.html
Fabrice Bellard: http://bellard.org/
viraptor · 2016-04-05
Here's another blog if you want to ever follow up with more advanced "this can be done" examples: http://www.windytan.com/p/posts.html
whoopdedo · 2016-01-20
Did you know each manufacturer had a unique sound for their v90 handshake? This one sounds like a Lucent WinModem. (Based on listening to the sounds here[1]. Yay for RealAudio!) The USR/3Com modems were two "bongs" (four if the higher speed failed). But I was always fond of the Rockwell sweep[2].
Of course, required reading is HN favorite Oona Räisänen's excellent analysis of a modem handshake.
[1] http://modemsite.com/56k/trouble3.asp
[2] https://www.youtube.com/watch?v=vvr9AMWEU-c
[3] http://www.windytan.com/2012/11/the-sound-of-dialup-pictured.html
as1ndu · 2015-10-04
As an introduction to signals, The Scientist and Engineer's Guide to Digital Signal Processing is pretty good(http://dspguide.com/)
you should also read this woman's blog http://www.windytan.com/
EliRivers · 2015-07-11
The author of this, Oona Räisänen, is one of my standard examples of someone who is genuinely a hacker in the proper (by which I mean, the Stephen Levy "Hackers" definition; if you want to use the prior MIT prankster meaning, I won't stop you) sense.
This post of Oona's - http://www.windytan.com/2014/02/mystery-signal-from-helicopter.html - in which she extracts, from the audio of footage from a news helicopter, the location of that helicopter, is an excellent example.
Given that someone here recently defined "hacker" to me as "person who can write code", the word is in serious danger of being so devalued as to be useless.
fnordfnordfnord · 2015-05-21
See also: http://www.windytan.com/ and https://twitter.com/0xabad1dea
ptaipale · 2015-02-13
Oona Räisänen writes some remarkable stuff. Not maybe so much about manufacturing and quality of electronics, but building and reverse-engineering stuff. I've been baffled time and again by her talent.
http://www.windytan.com/
JonnieCache · 2014-11-03
Fabulous stuff.
Microwave mapping fans will also enjoy the following post from windytan: http://www.windytan.com/2014/07/mapping-microwave-relay-links-from-vid…
mmastrac · 2014-08-29
On the flip side, the people most likely to do things like this are also most likely to set up their own site somewhere and keep it running. For instance, http://www.windytan.com/ (Oona Räisänen) and http://tronixstuff.com/ (John Boxall).
nl · 2014-02-01
I love this:
Several people in the restaurant were waiting for orders with their similar devices, which suggested to me this could be a pager system of some sort. Turning the receiver over, we see stickers with interesting information, including a UHF carrier frequency. For this kind of situations I often carry my RTL2832U-based television receiver dongle with me (the so-called rtl-sdr).
I knew I was forgetting something.
http://www.windytan.com/2013/09/the-burger-pager.html
h2odragon · 2021-07-30
also: http://www.windytan.com/
wkjagt · 2025-09-05
Some of these, including one I had as a kid, produce sound through a small gramophone inside. No electronic amplification at all, just a needle on a tiny "record", mechanically connected to some kind of speaker shaped cone.
Here's someone taking apart the exact robot I had, and showing that mechanism: https://www.windytan.com/2013/02/the-atomic-powered-robot.html
kiicia · 2025-06-28
This reminded me of „Ultrasonic investigations in shopping centers”[1]
> Ultrasonic pilot tones, commonly used in PA systems to monitor speaker connections, are often modulated by background noise or movement. These tones can be used for various purposes, such as speed detection, escalator monitoring, positioning codes, ad delivery, and finding quiet areas in shopping centers.
[1] https://www.windytan.com/2024/06/ultrasonic-investigations-in-shopping…
melenaboija · 2024-10-27
This is the blog post[1] from the presenter explaining part of it, with this request in the messages lol:
- Sad to request, but can you take thisoffline. It is kind of our service you hacked :)
[1]https://www.windytan.com/2013/05/a-determined-hacker-decrypts-rds-tmc.…