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Building Alert: Construction Issues ...........................................................

The ferrite rod that you wrap wires around to make a coil is brittle. If you

drop it or knock it against something, it could easily break, so be careful!

If you place your radio in a wooden box (as we did), check the thickness of

the wall of the box against the length of the threads on the potentiometer.

Because the wall on our box was^1 ⁄ 4 " thick (the same thickness as the threads

on the potentiometer), we just put some glue between the body of the poten-

tiometer and the wall of the box (making sure not to get glue on the rotating

shaft). You might want to use a chisel to reduce the thickness of the wall so

that the rotating shaft sticks out a little farther; that way, the knob doesn’t

end up too close to the face of the box.

The variable capacitor has very small holes in its metal body that you can

use to mount it on small pins. Again, we found it easiest to glue this to the

wall of the box after chamfering(cutting a furrow in) the edge of the hole to fit

the metal knuckle around the shaft. In this way, the wall of the capacitor fits

flush against the wall of the box.

Perusing the Parts List ................................................................................

Get ready to turn on your computer or head to the electronics supply store

to shop for the parts for your radio project (several of which are shown in

Figures 8-3 and 8-4). Here’s what you’ll need:

10 kohm potentiometer (R1)

10 ohm resistor (R2)

Two 0.01 microfarad ceramic capacitors (C1, C3)

One 0.1 microfarad ceramic capacitor (C5)

Two 0.047 microfarad ceramic capacitor (C4, C9)

10 microfarad electrolytic capacitors (C7, C6)

100 microfarad electrolytic capacitor (C8)

LM386N-1 amplifier IC2

You’ll find many versions of the LM386 amplifier. We chose the LM386N-1

because it works with the supply voltage of 6 volts used by this circuit.

Battery pack for 1 AA battery

Chapter 8: Surfing the Airwaves 169