The signal from this transmitter is injected into a cable that you want to follow along a pipeline. Monitoring is done using an ordinary AM receiver out of season.
This circuit is from a 1954 transistors publication. The transistors are the CK722 among the first...
We adapt this circuit of Radio Electronics - March 1990. The magazine no more exists, but the...
This circuit uses a dual floodgate MOSFET not very easy to obtain today. Its handling is very...