[Jeija] was playing with some ESP32s and in true hacker fashion, he wondered how far he could pull them apart and still get data flowing. His video answer to that question covers the Friis equation and has a lot of good examples of using the equation, decibels, and even a practical example that covers about 10km. You can see the video below.
Of course, to get that kind of range you need a directional antenna. To avoid violating regulations that control transmit power, he’s using the antenna on the receiving end. That also means he had to hack the ESP32 WiFi stack to make the device listen only on one side. The hack involves putting the device in promiscuous mode and only monitoring the signals being sent. You can find the code involved on GitHub (complete with a rickrolling application).
Of course, antennas are nothing new–look at all the Pringle can antennas we’ve seen in the past. However, the use of a long range receive-only module is interesting and we can see this technique having applications to remote drone video or telemetry and — of course — wardriving. If you don’t have a big boss antenna lying around, you might try some duct tape. If you want a more detailed refresher on decibels, we did that last month.