This simple tester was found in a Popular Electronics from the 90s. The circuit is powered by two 9 V batteries since it requires a symmetrical source.
This circuit was found in Radio Electronics magazine from June 1961. The distance between stations is...
We found this circuit in a European publication from the 1970s. The transistors are made of...
This circuit is from a factory manual from the 80s. The circuit can be implemented with more...