Remember to use a good ferrite Am radio coil, use the images of the top for to guide you, if you decide to construct the coil please make it for Am Radio especially designed. If you have some problems listening the frecuency or the station are so difficult to hear you can CHANGE THE R4 RESISTOR FROM 2K7 TO 3K3 if whistles appears. If you have other type or other model of air capacitor you can try diferents tipes of conection or to searh the diagram in google, remember you can probe if the circuit is working if you connect a earphone between collector of transistor Q2 and POSITIVE (+) of the battery. Speaker may be any little speaker but with high impedance more tha 4ohms for better results but you can to use anyone you want :) R2, R3 Y C5 polarize the transistor and give him more gain. Q3 works as a driver of the speaker for amplify in a retroalimetation configuration. R4 delimit current and the frecuency of sintonizacion for to polarize the transistor Q2Ĭ1 & R5 is a configuration for make the sintonization between teh ferrite coil and the variable capacitor. Q1 y Q2 are a cascade darlington transistor array for amplify the current. The ferrite coil from am radio and a variable tunning capacitor sintonize the frecuency and the other circuits is amplification and selectivity. We'll need some electronic components and any other thinks that you like to add for modify the radioģ- NPN TRANSISTORS (I RECOMMEND YOU TO USE GERMANIUM TRANSISTORS AC187) OR 2N2222 ANY GENERAL PURPOSE TRANSISTOR.ġ- VARIABLE CAPACITOR FROM AN OLD RADIO O FROM RADIOSHACK STOREġ- FERRITE COIL (ANTENNA AM RADIO) FROM AN OLD RADIO TOO.ġ- 3k3 Resistor (if whistles appears in the output cound you can to change the value between 2K7 TO 3K3 ohms).ġ- Little Speaker (you can to choose add plug for earphones).ġ- 1.5 V Battery (AA/AAA/C/D) anyone you have.ġ- Wood enclosure or anyone you have it's for to protect the proyect and have better look.ġ- dill or anything to make the holes in the enclosure.ġ- PCB board of cooper for to make the circuit.
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