Detecting a 2.4 GHz transmission for under 1 EUR
chzsoft.de
chzsoft.de
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.
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.
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.
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...
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.
It will light up near wifi/bt sources.
As far as I can tell the Analog Discovery you mention is quoted by Digilent at $279 and for this price you get two 100MS/s analog inputs, so that means that you can't sample anything above 50MHz max (and in practice you probably won't be able to do a lot of useful work above ~40Mhz). With modern circuits routinely having signals in the hundreds of MHz that's fairly limiting for me.
And if I just want to probe "slow" digital signals like SPI or I2C I can get 90% of the features of this module by using a cheap-o ~$10 Saleae clone off aliexpress. It's only a digital analyzer but it goes up to 24MHz and with 8 channels you can already do quite a lot of work for a tiny fraction of the price of an entry-level scope.
Of course if you do a lot of analog work then a digital analyzer won't cut it and the ~$300 price tag for a basic scope is almost a required purchase at this point.
This comment dismisses a lot of measurement use cases out of hand, at least as far as a hobbyist or rudimentary manufacturing test case is concerned. An input bandwidth of 50MHz is still more than sufficient to evaluate all kinds of useful circuits - a few I can think of offhand:
* Buck regulator loop compensation and transient response * Large signal audio debug (not suitable for small signal just due to the limits in the analog frontend and the number of bits in the scope ADC) * Basic digital protocol debug
If you're tuning a PLL, or need to evaluate DDR signal integrity, or trying to design an audio system with -120dB of THD+N, then yeah, an Analog Discovery is probably not the right tool. Then again, if you need to do any of those work items, then you probably already know that.
RPi: $35
Battery: $15
Screen: $35
hm.
My big problem with a USB oscilloscope is that they are only ground referenced through the USB ground to your computer and if you measure something with a different ground reference you can blow up the USB port on your computer.
Gauging from the job postings on their website, I have a hunch/dream that the folks at Saleae are cooking a decent USB scope up as their next product offering. Would love it if they did. Saleae's Logic Pro 16 is without a doubt the best designed EE tool I've ever used.
Am I missing something? Does the diode have to be germanium for this trick to work?
A regular silicon diode will not work. An appropriate Schottky silicon diode will do the job; see the Infineon app-note in the "PPS" of the website. Also, the point-contact (regardless of the semiconductor material) reduces the diode's junction capacitance, making it faster, i.e., more suited for RF applications.
It's a neat hack! Long live the Rigol DS1054Z!