Radio

Radio

Introduction

In this paper we are going to analyze the process of the manufacturing of a galena radio. A galena radio is a radio receiver that uses a semiconductor crystal lead sulfide, also called galena to capture radio signals in AM; this is the simplest we can build. Then can listen am without any kind of external power as batteries only coming from the antenna. This is a very simple radius used since the beginning of the century. Before they were invented vacuum tubes and transistors, radio receiver's primitives were galena. It was extremely simple devices, with very few components, and even power needed for operation, basically a crystal consisting of a coil, a crystal detector (galena) and headphones. Today anyone could build a crystal set, although the lead ore (lead sulfide) is hard to get now, replaced by a component that can be purchased at any electronics store (Mende, 1974).

Discussion

Elements in manufacturing a Galena Radio

Antenna

It goes without saying that the antenna is a key element. The standard AM band is in the range of 0.530 and 1.6 MHz, which corresponds to a wavelength of approximately 145 meters. A half-wave antenna would be about 72 meters long if a dipole. One possibility is to build a ¼ wave antenna with 4 stakes to form a square about 8 feet square.

Grounding

It's just a cable connected to a pipe or a metal bed frame. It would be ideal if we could have a real earth through copper piece buried in a well wet.

Tuning coil

It is a necessary component to a resonant circuit tuned stations. 400 turns of enameled copper wire of 0.2 mm in section, on a cylindrical support 3 cm. in diameter and 10 cm. in length, leaving an air outlet 50 turns each and a small rim of half centimeter without winding at each end. To move the thread can be covered with paraffin we can get from a single candle. The support may be a PVC pipe utilized for driving the water. The enameled copper wire can be purchased at any electronics trade (Calhoun, 1994).

Variable capacitor

It is a collection of two metal plates that rotate on an axis parallel to each other, but without physically touching, and that more or less closing provide greater or lesser surface, and therefore a greater or lesser electrostatic capacity. It is a necessary component for varying the resonant frequency of the coil, so you can move from one point to another dial, letting only one of the signals coming from the entire antenna. The capacitor can be to an old radio, valves or transistors, but can also be easily purchased; its capacitive value should be at least 450 or 500 pF.

Galena detector diode RF signal

The diode is a necessary component to rectify the RF current and voltage passing only the audio signal, which will later become sound in the head phones. As will be difficult to get the ore galena, buy and use instead a simple type ...