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https://github.com/RamboRogers/rfhunter
This project is an RF Signal Scanner built using an ESP32, AD8317 RF detector, and various other components. It's designed to detect and measure RF signals in the environment and display the signal strength on an OLED display. It's useful to find hidden cameras, wiretapping devices, and other RF-enabled devices.
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RFHunter V4.0 - RF Signal Detector
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Your object is to save the world, while still leading a pleasant life.
(Score: 5, Interesting) by VLM on Tuesday October 29 2024, @12:05PM
The chip is spec'd down to 1 MHz but works lower (its an old chip from just after Y2K and I played around with it in the past) so it kinda-sorta works for EMI/EMC screening but not so well. You can pick up a lot of switching power supply noise below 1 MHz but its not spec'd for that although it will respond somewhat.
The chip goes to some effort to generate a pretty good dB ratio measurement which might or might not be overkill for some applications. It outputs an analog voltage not I2C so its not overly precise. I vaguely remember "dozens of mV per dB" slope in output voltage. So if you stuck a -10 dB standard on the input you'd get some random voltage around "whatever" and then if you stick a 3dB attenuator inline the voltage will drop (I think?) by precisely 25*3.000 mV, the delta will be pretty precise, but its anyone's guess what the starting and ending voltage will be. If you slapped a relay on the input with good isolation (good luck finding a cheap one) your software could autocorrect itself, including if you had amps/filters/attenuators on the input. So that's cool.
It's "only" linear over a range of maybe 40 to 50 dB from memory.
General aliexpress cost for the RF board with SMA connector ready to wire to a microcontroller is under "six dollars" and its a 5V tolerant chip so it'll work with pretty much anything (not ESP32 specific)
Its an old chip from the 00s, you could buy a Ramsey Electronics kit that used it in the 00s, they work pretty well. Fundamentally this chip/dev board is a magic black box that turns around 0 to -50 dB from 1 MHz to 10 GHz into an analog voltage that has a constant-ish linear change with dB change in input, and the rest of the project / kit is merely a voltmeter with a fancy display and some power supply, etc, more or less. If you just want to F around with the chip on the lab bench literally all you need is 5V and a voltmeter. IIRC the output impedance was rather large so forget driving a LED directly its meant to feed opamps or comparators or a microcontroller A/D input.
If you're doing EMI/EMC and just looking for signal, or doing generic "peak for max output" tuning, then just use a diode with a voltmeter clipped across it. Or if you're doing "serious RF work" like getting a multiplier peaked up on the correct peak, use a spectrum analyzer. But for some simple uses, this can be a good chip.
I believe it was originally developed / marketed for IF "RSSI" meter purposes (although not as low as 455 KHz), so if you're doing something very vaguely like that, the chip will work very well indeed.