One of the great things about the Hackaday community is how quickly you find out what you don’t know. That’s not a bad thing, of course; after all, everyone is here to get smarter, right? So let’s work together to get our heads around this paper (PDF) by [Zerina Kapetanovic], [Miguel Morales], and [Joshua R. Smith] from the University of Washington, which purports to construct a low-throughput RF transmitter from little more than a resistor.
This witchcraft is made possible thanks to Johnson noise, also known as Johnson-Nyquist noise, which is the white noise generated by charge carriers in a conductor. In effect, the movement of electrons in a material thanks to thermal energy produces noise across the spectrum. Reducing interference from Johnson noise is why telescopes often have their sensors cooled to cryogenic temperatures. Rather than trying to eliminate Johnson noise, these experiments use it to build an RF transmitter, and with easily available and relatively cheap equipment. Continue reading “A Single-Resistor Radio Transmitter, Thanks To The Power Of Noise”
Throughout history, people have devised ways to send information across long distances. For centuries we relied on smoke signals, semaphores, and similar physical devices. Electricity changed everything. First the telegraph and then radio transformed communications. Now researchers at the University of Lancaster have demonstrated another way to send wireless data without using electromagnetic radiation. They’ve harnessed fast neutrons from californium-252 and modulated them with information with 100% success.
The setup was interesting. The radioactive material was encased in a cubic meter steel tank filled with water. A pneumatic system can move the material to one edge of the tank which allows fast neutrons to escape. A scintillating detector can pick up the increased neutron activity. It seems like it is akin to using what hams call CW and college professors call OOK (on off keying). You can do that with just about anything you can detect. A flashlight, knocking on wood, or — we suppose — neutrons.
We wondered what the practical application of this might be. The paper suggests that the technique could send data through metal containment structures like those of a nuclear reactor or, perhaps, a spacecraft where you don’t want anything unnecessarily breaching the containment. After all, neutrons cut through things that would stop a conventional radio wave cold.
It seems like you only have to prove you can detect something to make this work — it really doesn’t matter what it is you are detecting. It seems like it would be much harder to do more advanced types of modulation using neutrons. Maybe this is why we don’t hear aliens. They are all Morse code operators with neutron-based telegraphs.
The first generation of The Internet Of Things™ and Home Automation devices are out in the wild, and if there’s one question we can ask it’s, “why hasn’t anyone built a simple cracking device for them”. Never fear, because [texane] has your back with his cheap 433MHz OOK frame cloner.
A surprising number of the IoT and Home Automation devices on the market today use 433MHz radios, and for simplicity’s sake, most of them use OOK encoding. [Texane]’s entry for THP is a simple device with two buttons: one to record OOK frames, and a second to play them back.
Yes, this project can be replicated with fancy software defined radios, but [Texane]’s OOKlone costs an order of magnitude less than the (actually very awesome) HackRF SDR. He says he can build it for less than $20, and with further refinements to the project it could serve as a record and play swiss army knife for anything around 433MHz. Video demo of the device in action below.
Continue reading “THP Entry: A 433MHz Packet Cloner”