"If one wants to make it more sensitive to certain frequencies than to others, one needs to add a resonant circuit, usually a combination of an inductor and a capacitor"<p>Coincidentally for OP, the ideal antenna element length for a 2.4 ghz dipole antenna is around an inch and a quarter, which handwavy looks like about how long his diode leads are.<p>Even a pitiful attempt at a tiny air wound coil choke would decouple his scope probe wires from interfering with the natural dipole antenna pattern.<p>I bet, that if OP decoupled his scope probe wires, he could plot the natural radiation pattern of a dipole by rotating the diode and its antenna around and noting the voltage on the scope at various angles relative to the transmitter. If I have time I'll try that in the lab today just for fun.<p>All it'll take is a couple inches of hookup wire... OR more sneakily could coil the diode leads themselves at the correct distance from the diode... Or I could tack solder some coaxial cable and BNC connector with a sloppy homemade choke balun ... hmm...<p>I bet for TWO EUR I could plot antenna radiation patterns pretty reliably. I wonder if OPs mouse has a horizontal or vertical polarized antenna? I bet I can test that for two EUR.
An even simpler recipe from me. Get an epoxy cased LED and twist its leads around a schottky, polarity reversed.<p>It will light up near wifi/bt sources.
I've done something kind of similar (but much less low-level) using the nRF24L01+ attached via SPI on the GPIO pins of a Raspberry Pi Zero. I'm in the middle of writing it up, but it will probably be a couple of weeks.
Opinion: HN should have the equivalent of folders/tags for articles; this article and others like it would be perfect for a folder/tag marked "Cool Hack For Under $10" -- or some designation similar to that...
I've never understood why germanium diodes are special here.<p>Am I missing something? Does the diode have to be germanium for this trick to work?