Mechanical engineer Florian Wilhelm Dirnberger has tried out a design for constructing a “very primary” radio frequency (RF) detector — utilizing a Texas Devices LM1458 twin op-amp and a speaker to show RF power into audible sound.
“The idea of this radio frequency detector (initially marketed as [a] ‘Radar Detector’) is something however new and schematics are floating round in books and on the web for many years,” Dirnberger writes of the undertaking, “however barely anybody ever appear to have truly constructed this explicit system so I made a decision to check whether or not it’s a viable design (it’s, form of).”
The detector is constructed with minimal elements, the central of which is the TI LM1458 twin op-amp with a handful of resistors and capacitors. There is no microcontroller, and nothing that might be recognizable as a radio receiver — the detector as a substitute engaged on the precept of rectification. As an RF transmitter — whether or not intentional or in any other case — nears the circuit, the power enters the enter of the op-amp together with the supposed sign.
Whereas such radio-frequency interference is often notable just for how one can take away it out of your design, on this case it is the entire function of the circuit: choosing up RF indicators from the aether and amplifying the interference they create to generate a brand new sign which could be fed via one other amplifier and right into a speaker.
“Capacitor C1 is the figuring out half right here. Shortening its pins could or could not improve the efficiency drastically (assessments ongoing). The worth itself shouldn’t be so crucial (must be within the nF vary although),” Dirnberger writes. “You possibly can e.g. join a LM386 amplifier and a speaker on the OUT Pin, however perhaps you guys have a greater suggestion what to do with the output sign.”
The complete undertaking write-up is accessible on Dirnberger’s Hackaday.io web page, together with a schematic for the circuit.