In the early years of radio, the acquisition of receiving equipment was expensive, so many people made homemade devices called galena radios. Nowadays, with few materials and by changing the galena for another material with similar characteristics, we can make an AM radio receiver home-made in a very short time.
– Una varilla de ferrite de 18 cm de longitud (El ferrite es un colorante de cemento que se consigue en ferreterías).
– Un condensador de 100 pF.
– Un diodo IN60.
– Un audífono de alta impedancia.
– Dos conectores tipo cocodrilo de tamaño pequeño.
– Antenna for radio.
– Conexión a tierra.
– Alambre de cobre esmaltado de 1mm de espesor.
Construction of the receiver
To begin construction of the radio receiverIn this way, we make a cylinder of cardboard with a length of 17 cm and a diameter large enough for our ferrite rod to slide through.
Once the cylinder is made, we make the winding in the following way: we start at one end of the cylinder and with the copper wire we make about 8 turns and leave a bit of wire protruding (for tuning), we cut the wire and we make a new winding of 8 turns right next to it. We repeat this procedure until we get about 80 turns or 10 different windings.
When the winding is finished, we can place the tube on supports to prevent the assembly from disassembling. Once the winding is fixed, we take a connection at both ends of the winding and connect the capacitor.
Now, we mount the diode in such a way that it is sufficiently fixed to prevent it from disassembling. Also, we make the ground connection, which can be done in a nearby pipe or a previously grounded socket. The electrical assembly can be seen in the following figure.
Next, we locate the antenna of the receiver Just above the coil, care should be taken to position the antenna as high as possible. The antenna should be approximately 15 cm long, remember that the longer the antenna, the better the reception.
Once the radio has been assembled, all that remains is to tune the stations. To do this, we place the crocodile connectors in two of the nine connections that we created in the coil and carefully move the ferrite bar that is inside the cardboard. Remember that the porosity of the ferrite rod is vital for the tuning of the stations, which we can hear thanks to the magnetic field created by the winding.