This circuit was found in documentation from the 1970s. However, it can be implemented with modern transistors such as 2N2222 for Q1 and BF494 for Q2. The crystal depends on the desired frequency.
This single channel circuit can be used with one of the many receivers that we describe in this...
This simple experimental circuit using only transistor produces a tone given by C1 and C2. Tone is...
This version of the previous circuit, also from Radio Electronics magazine of July 1970, uses R4...