This receiver was found in an article in Electronics Now magazine in March 1994. The coils are critical, as shown in the figure. Listening is through headphones.
Using bipolar, FETs and unijunction this long-lasting timer can reach 10 hours with good quality...
This 1-transistor circuit for currents up to 50 mA was found in the August 1974 Radio Electronics...
We found this circuit in a 1969 General Electric documentation. The circuit uses transistors of the...