Found in an Elektor from the 90s, this circuit converts signals from the 280 kHz band to 516 kHz, making it possible to tune them in common AM radios. The components used are from that time.
This non-inverting AC amplifier was found in the February 1990 issue of Radio Electronics...
This sensor circuit for a small robot was found in a Popular Electronics from the 90s. The circuit...
This direct detection circuit was found in a 1986 documentation. The output is of low power, but...