I’ve gotten into the practice of replacing the trace antennas on bluetooth receivers with 1/4 wavelength monopole antennas in the hopes of getting more range. I have a stereo in the garage in particular, and I’d like to be able to reach it from a computer transmitting inside. This has been fairly successful, although I think I should go back and experiment with length now that I have found some tools to measure the signal strength. The length of the antenna should be fairly key to getting maximal reception.
Along the way, I found an in depth document describing the ins and outs of common bluetooth antenna designs. One tidbit: the usual trace antenna I see on bluetooth boards has a theoretical gain of 1.6dB, while the monopole I spent so much time hacking into place only has a theoretical gain of 2dB. Doesn’t sound like a big difference. Yet on all the sites describing DIY bluetooth monopole antennas, the gains they see are huge. My gains seem more in line with the document, and maybe the difference for free air is much greater (even at the same ratio) than where I’m using it, trying to get through a couple walls and some noise sources.
