This circuit was found in a 73 amateur radio magazine from the 90s. An LED extends the scale from 0 to 5 V to 10 to 15 V in this bargraph circuit. Other zener values can be used.
This simple 60's receiver is powered by solar cells of the time. The transistor is made of...
VR can be from 50 to 220k it is recommended to connect a 100-ohm resistor in series. The lamp may...
This circuit provides precise signals of three frequencies, using CMOS technology. The integrated...