1. Description

The concept of this radio frequency detector (originally advertised as "Radar Detector") is anything but new, and schematics with the LM1458 OPV are floating around in books and on the internet for decades. 

Yet barely anyone ever seem to have actually built this particular device so I decided to test whether it is a viable design (it is, sort of).

2. Schematic

Capacitor C1 is the determining part here. Shortening its pins may or may not increase the performance drastically (tests ongoing). The value itself is apparently not so very important (should be in the nF range though).

One can connect a LM386 amplifier and a Speaker at the OUT Pin for an immediate feedback, but maybe you guys have a better suggestion what to do with the output signal (see example oscillogram photo).

3. Demo video

Tests with various radio frequency emitting items, such as a Raspberry Pi Pico W, a Bluetooth Low Energy module, and a mobile phone.

4. "Radar detector"

Military and civil radar operates (or used to operate) also in the lower GHz regions (S-Band and L-Band). Example: Airport Surface Detection.

So it would be possible to detect these high frequency sources with this device, at least in principle.