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 mission, “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, type of).”
The detector is constructed with minimal parts, the central of which is the TI LM1458 twin op-amp with a handful of resistors and capacitors. There isn’t any microcontroller, and nothing that will be recognizable as a radio receiver — the detector as an alternative 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 may be fed by means of one other amplifier and right into a speaker.
“Capacitor C1 is the figuring out half right here. Shortening its pins might or might not improve the efficiency drastically (exams ongoing). The worth itself will not be so essential (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 mission write-up is on the market on Dirnberger’s Hackaday.io web page, together with a schematic for the circuit.