0-30 VDC STABILIZED POWER SUPPLY Schematic
This is a high quality power supply with a continuously variable stabilised output adjustable at any value between 0 and 30VDC. The circuit also incorporates an electronic output current limiter that effectively controls the output current from a few milliamperes (2 mA) to the maximum output [...]

A photo of the Revision-A preamp is shown below. You’ll see that there are two dual opamps, but the schematic only shows one. This is the main part of the Rev-A update – the output section now has gain (which is easily selected), and a better buffered low output impedance. The remainder of the circuit [...]

The circuit of AM transmitter is designed to transmit (amplitude modulated) DSB (double side band) signals. A modulated AM signal consists of a carrier and two symetrically spaced side bands. The two side bands have the same amplitude and carry the same information. In fact, the carrier itself coveys or carries no information. In a [...]