Circuit Project Electronic

This idea presents a simple circuit for a superhet radio receiver that can be built up in sections, with each section tested before assembly. The receiver circuitry as presented here can be built for less than $50.
Don’t be misled—even though the set has some pretty obvious limitations as presented, it’s still capable of worldwide reception [...]

Cell phones aren’t the only devices to benefit from ever- smaller and more highly integrated communications-IC technology. The simple, three-IC superheterodyne radio in Figure 1 can receive stations in the 4.5- to 10-MHz range from around the world with only a 10-ft antenna. A superheterodyne radio works by mixing the incoming RF signal with a [...]

This circuit uses a 1458 dual op-amp to form a radar detector. C1 is the detector of the radar signal. The first op-amp forms a current-to-voltage converter and the second op-amp buffers the output to drive the piezo transducer. R5 sets the switching threshold of the second op-amp; normally it is adjusted so that the [...]