understanding, customizing, and hot-rodding ... - Suono Elettronico

inging your hand nearer to the antenna. In normal
theremin playing, hand capacitance is less than one
picofarad, a very small capacitance change indeed!
In addition to hand capacitance, a theremin antenna
has a fixed capacitance to ground, which we'll call
the antenna capacitance. Antenna capacitance
depends mostly on the size of the antenna, and is
typically 10-15 picofarads.
A large inductor, called the antenna coil, is
connected to each antenna inside the theremin. The
antenna coil, antenna capacitance, and hand
capacitance form a resonant circuit (Figure 1). In our
design, the resonant frequencies are about 285 kHz
for the pitch antenna, and about 450 kHz for the
volume antenna. At or near the resonant frequency, a
tiny change in hand capacitance results in a larger
change in the impedance of the antenna circuit as a
whole.
Figure 1 - Equivalent Circuit of Hand Capacitance
THE ETHERWAVE CIRCUIT
Before looking at the schematic diagram itself, we'll
review the functions of the Etherwave's circuit.
Figure 2 is a block diagram showing all the circuit
functions.
Figure 2 - Etherwave Block Diagram
UNDERSTANDING, CUSTOMIZING, AND HOT-RODDING YOUR ETHERWAVE - PAGE 2