61–70 of 125 posts
Does anyone know a way to receive these signals without installing extra hardware? Then we need a name for it. DarkFi?
reversing the LEDs of the screen to become an input, the LED screen works as a basic light sensor
(only the very tiniest bit related, for the BBC micro:bit)
Earlier quoted context omitted.
For a really good time, I suggest https://github.com/JamesP6000/WsprryPi - it is super fun run a signal into a long wire and see it picked up around the world! (You do need an amateur radio license for this, but in the USA at least the technician one is very easy to get.)
For the semi-serious there is a pre-made filter "temporarily unavailable" (2018-01-15) for purchase: Raspberry Pi QRP TX Shield for WSPR | https://www.tapr.org/kits_20M-wspr-pi.html the harmonics are filtered by a LPF, and the broadband noise is filtered by a BPF [...] a buffer amp is provided for isolation. This also provides a boost to the TX signal And this project ties in an RTL-SDR for receiving: https://github.…
Back a couple of decades, my alphabetic pager was going off but the messages were gibberish. It turned out the CPU in the PC I'd been asked to look at was a Pentium running at 150 MHz. I'd set my pager directly on top of the case, and the nominal frequency for it was 150.5 MHz, frequency modulated. The lines in the motherboard can be used as antennae and the CPU pins can produce a clock pulse and modulate it. There u…
Earlier quoted context omitted.
For the semi-serious there is a pre-made filter "temporarily unavailable" (2018-01-15) for purchase: Raspberry Pi QRP TX Shield for WSPR | https://www.tapr.org/kits_20M-wspr-pi.html the harmonics are filtered by a LPF, and the broadband noise is filtered by a BPF [...] a buffer amp is provided for isolation. This also provides a boost to the TX signal And this project ties in an RTL-SDR for receiving: https://github.…
Building your own LPF is surprisingly easy and educational!
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Years ago I was in the same building during the installation of a "NATO standard" (whatever that means) environment suitable for developing sensitive software, and the air gap was indeed pretty large, the entire 2 rooms were air gapped from the building (at 4th floor), enclosed in a Faraday cage and with special precautions (out of my clearance level) for electricity going in. It was very quiet inside (even cell phon…
Hopefully cellphones weren't allowed? Otherwise it would be interesting to hack the phone to go to "record AM signals" if there's no cell/wifi/FM/GPS signals (if it were on a plane it would still see GPS signals). Or maybe to announce its presence using ultrasonic, so if there's also compromised machines/CPUs/hypervisor environments inside the secured environment, it would detect the "Hello" and start uploading data…
Quite old trick actually. At Cold War time, in USSR, American spy device was discovered that was placed on the street outside the wall of main frame computer installation nearby drum printers ( https://en.wikipedia.org/wiki/Printer_(computing)#/media/Fil... ). The device was recording signals from them and retransmitted recording in compressed form to satellite.
https://pitchfork.com/reviews/albums/9583-ibm-1401-a-users-m...
I debugged a boot issue on the Apple Newton this way. The latest flash image was a brick on production hardware (no available LEDs, GPIOs, etc.) but not on development hardware. But I could flash a new OS image. So I wrote some small loops that did different stuff on the bus (so that they sounded different) and salted the boot path with them, then listened in on my portable AM radio. Found the problem inside of an ho…
Back a couple of decades, my alphabetic pager was going off but the messages were gibberish. It turned out the CPU in the PC I'd been asked to look at was a Pentium running at 150 MHz. I'd set my pager directly on top of the case, and the nominal frequency for it was 150.5 MHz, frequency modulated. The lines in the motherboard can be used as antennae and the CPU pins can produce a clock pulse and modulate it. There u…
Resistor ladder DA converters are pretty fun.
https://en.wikipedia.org/wiki/Covox_Speech_Thing
https://hackaday.com/2015/11/05/logic-noise-digital-to-analo...
https://www.tek.com/blog/tutorial-digital-analog-conversion-...