Using the 2N2646 this circuit was found in a Radio Electronics magazine from July 1968. The transistors are from the time and the lamp can be replaced by a high-power LED in a current version.
This circuit is for analog TV video signals and was found in the March 1988 issue of Radio...
The signal itself captured by the (long) antenna serves to feed this simple experimental circuit....
Although this project has only 3 digits, nothing prevents it from being modified to operate with a...