Found in Popular Electronics from the 90's, this tuned to infrared modulated receiver uses a PLL. The circuit has a signal strength indicator.
The signal itself captured by the (long) antenna serves to feed this simple experimental circuit....
This voltage level-triggered circuit was found in a 1969 Ferranti English documentation. Modern...
This amplifier makes use of a simple 12 to 30 W source, having been found in the SGS manual of...