Ivory sheets :
Le Ténor T35A
Le Sfr SRS4
by D. Lambert.
Exchanges between passionate persons can produce very positive results. You will find below, thanks to internet magic, the successful restoration of a vintage radio although its schematics were untraceable: the Sfer SRS4 set.
Technical pages :
Le tour du cadre
by D. Maignan.
We know that receiving radio waves with a loop in place of a wire antenna is possible. In that case, the receiver input is connected to an electrically closed circuit and the received signal is only the result of the induced current by the magnetic component of the high frequency field.
This almost exhaustive file will be published in several parts which appeals to some mathematical basic developments intended to sit the presentation, however aims at describing practical realizations within the reach of all.
Les ondes radio naturelles
by C. Beghin.
Les ondes de radioastronomie
The radioastronomy was born in the USA during the thirties thanks to works of genius radio engineers, the first one among them being without any doubt Karl Jansky, a Bell Telephone Company employee in New Jersey. By the end of the World War II, works were essentially performed by individual pioneers but they turned out in 1945 to make great strides thanks to a peaceful use of newly upcoming military radars. Since then, the ranges of frequencies and wavelengths came to grow up tremendously, from the Jansky’s SW range (decametric) up to microwaves lying near the bounds of the infrared astronomy, while the list of studied objects evolved towards the whole Universe.
Postes à galène néo rétro
by P. Dehayes.
The crystal sets: item often wholly studied, but which seems always so much fascinating for the amateurs! Indeed, what is more mysterious than hearing stuffs by only scratching a pebble!
The galena properties are known since the 19th century. It was commonly used to listen to radio during the twenties, when numerous passionated amateurs were often building their own receivers, thus opening the way of the vacuum tube reception.
Like them, let’s find the pure enjoyments of these first wireless enthusiasts, by building these small radio sets solely operated with the antenna energy!
In the course of Web :
Au fil du forum
by D. Maignan.
As everybody already knows, the Radiofil forum serves all early radio and audio technique amateurs. This is a great place of courteous chats where participants from all countries are discussing and exchanging very interesting information about their common hobby.
We are choosing and reproducing files useful to our readers, especially for those not ready to use the web yet.
In this issue, this section is dedicated to a cunning method to find out the polarity of an old earphone, followed by some exchanges about magnet magnetizing process.
History of techniques :
The epic of the crystal
by S. Melot.
Since the beginning of the wireless telegraphy, detecting the presence of an electromagnetic wave was the aim of numerous researches.
In 1889, Heinrich Rudolf Hertz builds a small device capable of revealing the existence of a radio wave. The Hertz detector resonator device allows a spark to be observed.
In 1890, Edouard Branly uses a glass tube filled with metallic filings and observes that the tube becomes a conductor when submitted to electromagnetic waves, while originally it was not. Connected to a battery, the current can be displayed on a galvanometer or can drive a relay.
In 1900, Captain Gustave Ferrié presents his electrolytic detector to the Academy of Sciences. Much easier to use, it is more sensitive than the Branly’s tube, but requires an adjustable bias source.
In 1902, Guglielmo Marconi develops an electromagnetic detector. Provided with a clock machinery, this sensitive, strong and voluminous device uses the magnetizing properties of a fine mobile steel cable crossing a high frequency coil and passing in front of magnets.
In 1904, John Ambrose Fleming invents the first vacuum tube (patent: 24850/1904). This two electrode tube exhibits good detector properties, but needs a consequent current source in order to obtain a good filament thermionic emission.
In 1909, Paul Jégou finalizes an electrolytic detector with a mercury-zinc mixture and a platinum electrode. This detector doesn’t require any bias source.
Radio Slovaquie Internationale
by H. Brien.
Since about fifteen years now, I have been collecting radio receivers with particular interest in multiband solid state models. I still use them from time to time for listening the international broadcast stations in short waves.
Un transfo d isolement
by P. Marsan.
La trousse a outil du dépanneur
Voici la liste des outils indispensables pour le dépanneur.