In this post, cnlohr has mapped the strength of his Wi-Fi signal in three dimensions. For this experiment he has used an ESP8266 embedded Wi-Fi module that can communicate any other Wi-Fi enabled device such as a laptop in this case. He’s also used some simple electronics to allow the ESP8266 to drive an LED.
While the ESP8266 can measure the signal strength of the Wi-Fi signals it receives, in this experiment, it is not being used to report that number. Instead his computer is connecting to and pinging the ESP8266. There’s an application on his computer that looks at the receive signal strength of those pings and based on that sends a color value to the ESP8266 which in turn then drives an LED accordingly. As the ESP8266 is moved around, the brightness and color of the LED varies depending on the signal strength, with Red and Blue colors representing strong and weak signals, respectively. The video below shows the experiment in detail.
What’s really interesting here is how rapidly the RF power changes with small changes in physical position as indicated by the color of the LED.
To improve the precision of his measurements he then used a CNC wood milling machine like this one to move the receiver, recording coordinates and signal strength.
Now you can likely understand why small variations in where you’re sitting in your living room can make a huge difference to the performance of your Wi-Fi network. Or why sometimes your cellphone works really well in one spot, but move a little to the left and the connection might drop entirely.