How to Design Schematic Circuit of AM Radio.

 This micro AM radio willtune strong stations in the frequency range between

530 and 1,600 kHz.

The circuit uses only one transistor as the amplifier and with a transformer

drives a smalloudspeaker. Asthe circuit is very poor in amplification, it needs

a long wire antenna. The antenna should be from 15 to 50 feet long for best

results. A good ground connection isalso important.

Of course, this is a small inexpensive transistor radio with low listening volume, particularly on a weak station. lf the station is too weak, replace the

SPKR by a low-impedance earphone.

The power supply is formed by two or four AA cells and current drain is very

low, extending their life. The circuit drains only few microamperes.

L1 is a tapped loopstick, connected to variable capacitor CV. These items

can often be found in non-working transistor radios, as well as the speaker

and transformer.

Figure I shows the schematic diagram for this project. Diode Dl acts as a

detector and Q1 as an audio amplifier. T1 is a common transistor output

transformer.

ln Figure 2 we show the components layout. All the components can be

housed in a small plastic box. A terminal strip is used as chassis in an experimentalversion.

T1 is a transistor transformer (1,000:8) and the SPKR is a miniature type.

But, if you have an unworking AM radio you can get these parts without spending any money.

To use, close Sl and tune to the desired station by adjusting CV. You can

adjust R1 for the best results according to your transistor gain.

Parts List - Micro AM Radio

Q1 - 8C548 general-purpose NPN transistor

D1 - 1N34 general-purpose germanium dlode

L1 - loopstick - see text

CV - 365 pF variable capacitor

T1 - Transistor transformer 1,000:8

SPKR - I ohms x 2 in. miniature speaker

R1 - 2,200,000 ohm, 114W,5% resistor

Cl - 0.1 uF ceramic or metal film capacitor

Sl - SPST toggle or sllde switch

B1 - 3 or 6V - two or four AA cells