How to Design Schematic Circuit of Noise generator

 The purpose of this simple experiment is to produce noise in the AM radio

band. The circuit can be used to show how brush motors and general appliances with motors can generate.noise in the radio band, interfering inradio,

TV, and radio communication services.

The circuit is very simple and the produced noise is too weak to cause any

problem to radio receivers. (FCC rules about noise and radio interference are

severe.) The noise produced by this experiment will interfere only in receivers

just a few teet away.

The schematic diagram of the device is shown in Figure 1. The heart of the

circuit is a small DC motor that works as a automatic key, producing rapid

variation in the current flow.

A mechanical view of the circuit, using a terminal strip as chassis, is shown in

Figure 2. All the components, including the power supply, can be fixed on a

plastic board.

Any small DC motor obtained from a nonworking toy can be used in this

project. The power supply depends upon the motor used.

CV and L1 can be obtained from any nonworking AM radio.

You can get more power for the RF noise by wiring a piece of wire to the

antenna (A) terminal, but limithis wire to no longer than 6 feet. Ll is formed

by 100 turns of No. 28 wire wound on a ferrite rod (diameter and length are

not critical).

By adjusting CV you can try to tune the signal to be stronger on a dead point

of the AM radio band.

Parts List - Noise Generator

B1       - 3 to 6V - cells or battery - see text

T          - Key or SPST toggle or slide switch

c1      - 0.1 uF ceramic or metal plate capacitor

CV    - 365 pF variable capacitor

L1    - loopstick - see text

M     - 3 to 6V DC motor