Found in a publication by Gernsback from 1960, this circuit uses germanium transistors of the time and commercial coils. It can be changed to operate with modern transistors and other wavebands.
With this circuit, signals in the range of 10 kHz to 150 kHz can be received at close to 4 MHz...
This limiting circuit with an operational amplifier has an adjustable cut-off point and can use...
Published by Philips in 1965 documentation, the sensor for this circuit is a common LDR. The...