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I’m curious how folks who have the know-how to dissect a phenomenon “miss the forest for the trees” when they stumble upon a “mysterious” signal. Alternate dat

by xattt 2y ago

I’m curious how folks who have the know-how to dissect a phenomenon “miss the forest for the trees” when they stumble upon a “mysterious” signal. Alternate data streams in FM like RDS, IBOC audio and FM time are not some new-fangled tech. This would/should be the first place to go to if you saw a signal that’s not modulated to analog audio. Of course, the whole mystery aspect is just a hook and helps move the story along.

therein 2y ago
Yeah more realistically it was like: > I was looking at FM radio channels on SDR (rtlsdr came out in 2010) and noticed the RDS. So I looked into it.
sriram_malhar 2y ago
Oona (the author) knew about the existence of such things; it wasn't a mystery. The only reason it was strange is that because her radio had been knocked about during a move, it was strangely down-shifting the data channel ... she was not monitoring the FM (from what I could make out), but the actual audio from the radio. This was just ('just' for her, impressive for me) an exercise of going down the rabbit hole, and then curating that tour for us.
- ezcrypt 2y ago
  Rather, I don't think the data channel was actually down-shifted, but that it wasn't filtered out (probably due to a broken analog filtering circuit after the fall), so it was still outside of the audible spectrum but available to the sound card and hence visible in her software spectrum analyzer. It also sounded like she was seeing some aliasing effect, i.e. that the data signal was probably out of band for the sound card ADC, but "folded" down into the sampler frequency range due to Nyquist folding "magic" (which is maybe what you meant with "down-shifting", now that I think about it?).
  - sriram_malhar 2y ago
    She does speak of aliasing.
dangsux 2y ago
[flagged]
- xattt 2y ago
  Look, I’m all for someone being excited for something they’ve never explored before. There is a joy in personal discovery of things you see. I’m not a fan of a fabricated premise in order to show “look how brilliant I am, I discovered RDS from first principles” when this mostly documented (1). In contrast, look at the Mike Harrison Eidophor talk. The guy pieced together a history of a significant technology that is otherwise poorly recorded on the Internet (2). This is new and novel info. (1) https://www.2wcom.com/fileadmin/redaktion/dokumente/Company/RDS_Basics.pdf https://www.2wcom.com/fileadmin/redaktion/dokumente/Company/... (2) https://hackaday.com/2016/04/19/mike-harrison-exposes-hot-oil-and-high-voltage-of-ancient-live-projector/ https://hackaday.com/2016/04/19/mike-harrison-exposes-hot-oi...
  - ezcrypt 2y ago
    I mean, she was pretty clear about why she found the signal, and that she read the RDS documentation in order to decode it, etc. I think the more fun part was towards the end, when she brute-forced decryption keys for traffic information coordinates and also found the (AFAIK) non-standard Finnish bus stop time table information in another band and reverse-engineered that, and I think that was the takeaway of the talk.
- spacecadet 2y ago
  Why does anyone need to? I would imagine billions of personal discoveries go unannounced every day. Is it a good use of resources to add more noise to world when you discover something that is already well documented? I don't think so, but then again everyone seems to have been trained to share personal discoveries like it's a grand discovery, for the sake of self advertising?
  - yellow_postit 2y ago
    Sharing and discovery is a fundamentally human act. It’s not noise. Celebrate people that want to learn, share and develop ideas. Obligatory XKCD “Ten Thousand” https://xkcd.com/1053/ https://xkcd.com/1053/

by xattt 2y ago

therein 2y ago

Yeah more realistically it was like: > I was looking at FM radio channels on SDR (rtlsdr came out in 2010) and noticed the RDS. So I looked into it.

sriram_malhar 2y ago

Oona (the author) knew about the existence of such things; it wasn't a mystery. The only reason it was strange is that because her radio had been knocked about during a move, it was strangely down-shifting the data channel ... she was not monitoring the FM (from what I could make out), but the actual audio from the radio. This was just ('just' for her, impressive for me) an exercise of going down the rabbit hole, and then curating that tour for us.

ezcrypt 2y ago
Rather, I don't think the data channel was actually down-shifted, but that it wasn't filtered out (probably due to a broken analog filtering circuit after the fall), so it was still outside of the audible spectrum but available to the sound card and hence visible in her software spectrum analyzer. It also sounded like she was seeing some aliasing effect, i.e. that the data signal was probably out of band for the sound card ADC, but "folded" down into the sampler frequency range due to Nyquist folding "magic" (which is maybe what you meant with "down-shifting", now that I think about it?).
- sriram_malhar 2y ago
  She does speak of aliasing.

dangsux 2y ago

[flagged]

xattt 2y ago
Look, I’m all for someone being excited for something they’ve never explored before. There is a joy in personal discovery of things you see. I’m not a fan of a fabricated premise in order to show “look how brilliant I am, I discovered RDS from first principles” when this mostly documented (1). In contrast, look at the Mike Harrison Eidophor talk. The guy pieced together a history of a significant technology that is otherwise poorly recorded on the Internet (2). This is new and novel info. (1) https://www.2wcom.com/fileadmin/redaktion/dokumente/Company/RDS_Basics.pdf https://www.2wcom.com/fileadmin/redaktion/dokumente/Company/... (2) https://hackaday.com/2016/04/19/mike-harrison-exposes-hot-oil-and-high-voltage-of-ancient-live-projector/ https://hackaday.com/2016/04/19/mike-harrison-exposes-hot-oi...
- ezcrypt 2y ago
  I mean, she was pretty clear about why she found the signal, and that she read the RDS documentation in order to decode it, etc. I think the more fun part was towards the end, when she brute-forced decryption keys for traffic information coordinates and also found the (AFAIK) non-standard Finnish bus stop time table information in another band and reverse-engineered that, and I think that was the takeaway of the talk.
spacecadet 2y ago
Why does anyone need to? I would imagine billions of personal discoveries go unannounced every day. Is it a good use of resources to add more noise to world when you discover something that is already well documented? I don't think so, but then again everyone seems to have been trained to share personal discoveries like it's a grand discovery, for the sake of self advertising?
- yellow_postit 2y ago
  Sharing and discovery is a fundamentally human act. It’s not noise. Celebrate people that want to learn, share and develop ideas. Obligatory XKCD “Ten Thousand” https://xkcd.com/1053/ https://xkcd.com/1053/