untitled

The following is a list of the schematic elements for your radio:

L1is a coil, or inductor. You make this by wrapping wire around a ferrite

rod. This coil is both the antenna and half the tuning circuit needed to

tune the radio to a particular station. The value of the inductor, given in

Henrys, is determined by the number of coils of wire you wrap around

the rod.

C2is a variable capacitor that forms a tuning circuit along with L1. When

you have a capacitor and inductor in parallel, the value of the capacitor

and inductor determine the resonance frequency,which is the frequency

of the radio station you tune in on your radio. As you change the value

of C2 by turning the knob connected to the capacitor, you change the

resonance frequency, therefore tuning in to a different radio station.

IC1is a ZN416E integrated circuit that is designed to separate the voice

signal from the radio frequency carrier and amplify the signal to a level

sufficient to power headphones.

C1 is a capacitor that allows nonresonant radio frequency signals to

conduct to ground.

C3, C4, and C5are suggested by the manufacturer of IC1; they shunt

high-frequency signals to ground, preventing them from causing noise in

certain parts of the circuit inside of IC1.

IC2,an audio amplifier named LM386N-1, takes the audio frequency elec-

trical signal generated by IC1 and amplifies it to provide sufficient power

to drive the speaker.

3

2

6

5

4

IC 2

C 7

C 9

R 1 +

• 
  

+6 V

+

+

C 8

R2

7

8

1

5

6

4 7

3

2

+1.5 V

C 1

C 2

C 3 C 5

C 4

IC 1

SPEAKER

+

8

1

C 6

L1

Figure 8-2:
The
schematic
of the radio
circuit.

Chapter 8: Surfing the Airwaves 167