The old maxim is that if you pay peanuts, you get a monkey. That’s no longer true, though: devices like the Raspberry Pi W have shown that a $10 device can be remarkably powerful if it is well designed. You might not appreciate how clever this design is sometimes, but this great analysis of the antenna of the Pi W by [Carl Turner, Senior RF Engineer at Laird Technology] might help remind you.
[Carl] used some fancy toys in his analysis, such as the awesome-looking antenna test chamber that his employer uses to test designs. He used this to measure two very interesting things; the radiation pattern of the antenna, and the efficiency. Simply put, the efficiency is a measure of how much of the energy you push into an antenna is emitted as RF radiation. There is always a little loss, but he found that the Pi W antenna has decent efficiency, with -3.5 dB losses at WiFi frequencies. That’s nowhere near as good as the stand-up antennas on your wireless router, but remember that the WiFi antenna on the Pi W is tiny compared to them: it is a small spot on the PCB made by removing several layers of copper, creating what engineers call a resonant chamber. That makes it a remarkable bit of engineering, keeping the cost down and using the copper layers that are already on the board to create the antenna rather than adding a new component.
The radiation pattern of the Pi W is also interesting. Because the antenna is located right on the PCB next to the HDMI and USB ports, you might expect that the signal would be much stronger in some directions than others. And you would be right: it seems that the metal shields of the two ports do block some of the radiated signals. However, it is worth remembering that WiFi signals also bounce around a lot, and other factors can influence how strong a connection is.
The final words of the analysis by [Carl] should be something that all hackers remember:
You can always learn things from clever designs and smart engineers. The amount of effort and creativity that has gone into this $10 computer is impressive—and the results speak for themselves.