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Radio amateur, September 1950, year I, number 9, price PLN 60.
CONTENT (1 cover page)
- Interference with radio reception.
- Let's learn radio technique.
- It's not difficult at all.
- Home loudspeaker installations.
- Radio probe.
- Diagrams of radio receivers T813.W and T813.GW.
- Rationalizer corner.
- Radio communications in the USSR.
- Radio engineering vocabulary.
- Editors' replies.
Diagrams of radio receivers types T813.W and T813.GW (cover page 2)
The presented diagrams show two popular radio receivers type T813.W and T813.GW.
The first of them, T813W type, is powered by alternating current, and the second - T813GW - by alternating or direct current from the lighting network. Receiving parts of radio receivers are assembled according to the same diagram. These are "simple", three-range, single-circuit receivers.
The T813W receiver has an AF7 electron tube, which acts as a detector, and an AL4 radio speaker tube.
Radio receiver type T813.W.
In the T813GW receiver the detector tube is VF7 and the speaker tube is VL4.
Radio receiver type T813.GW.
Both receivers use the same rectifying electron tube - AZ1. Both receivers have sockets for connecting a turntable, apart from the type, the T813W device has a switch that allows to reduce power consumption from the lighting network when listening to a strong local station.
Likewise, both receivers have permanent eliminators to eliminate interference in reception caused by the strong local station program. The setting of the waveband switches is adapted to receiving long waves.
The presented diagrams also show the voltages and currents (for both types of power supply) that should be in the individual circuits of the receiver. Knowledge of these values should facilitate the repair of the receiver.
The diagram of the radio receiver T813GW shows the connections of contacts on the board of the network switch for easier orientation during its repair.
Peace will win the war (1)
"The struggle for lasting peace, for the victory of fraternal coexistence among nations - is the most important task of the present generation. No one should doubt the final victory of this struggle, because the peace movement has become a movement of hundreds of millions of people today, and the ranks of active peace defenders are growing steadily. Nothing can stop the growth of this movement, because it is a movement for truth and justice in human relations. The strength of this movement is also based on the ever-increasing strength of nations liberated from capitalist violence, led by the mighty Soviet Union, led by the great peace standard-bearer Generalissimo Joseph Stalin. The Polish nation joins this fight for peace completely and with an unchanging will to win".
In these words delivered on September 2 this year to the delegation of the First Polish Congress of Peace Defenders - Bolesław Bierut, the President of the People's Republic of Poland, included the content of the struggle for peace waged today by the whole world. This was also the content of the session of the Warsaw Congress.
Interference with radio reception (2)
Contrary to atmospheric disturbances, the influence of which on radio reception is so strong that it often forces the device to be turned off and which almost cannot be avoided (see No. 6 of the magazine) - industrial disturbances can be effectively eliminated and can only be forced to abandon radio reception.
Interferences of this type are local in nature and come from electrical devices such as: AC and DC motors, vacuum cleaners, medical and hairdressing appliances, circuit breakers, etc. They most often manifest themselves in the form of tiring ear growling. Produced by the aforementioned devices - parasitic waves disrupting radio reception, they are most severe in large cities, industrial and health centers, where they create a "thick fog" which must be penetrated by radio waves sent into space by antennas of transmitting radio stations.
Let's learn radio engineering (5)
Cathode of electron tubes.
The basic electrode in any vacuum tube is the cathode. In order for the cathode to emit electrons, it must be heated to a relatively high temperature - several hundred or even over a thousand degrees. The cathode is heated with an electric, direct or alternating current. We have learned about two types of cathodes, namely direct heated cathodes and indirectly heated cathodes.
Direct-heated cathodes are usually made of tungsten wire, which in the case of small receiver tubes is usually activated by a track or bar, i.e. has an active layer of thorium or a layer of barium oxide on its surface in order to increase the emission efficiency of the cathode. The cathode wire on small receiver tubes is extremely thin. Its diameter is 10 microns, or 0.01 mm, while with high-power transmitting tubes whose emission reaches the value of 100 and more Amps, the diameter of the cathode fiber may be several millimeters..
Filaments for filing direct-glow electron tubes must be carefully suspended in the tube, and the finer the thinner the wire is. Usually, the cathode wire is suspended in one plane and it is in the shape of the letter "M" or the letter "V" inverted. The wire is suspended on springs, which is why it is subjected to a certain tension. This tension guarantees the suspension of the cathode in one plane and prevents the lateral warping of the wire during its heating due to thermal elongation of the wire. This ensures a constant distance between the wire and the anode or other electrodes in the tube (Fig. 1a and Fig. 1b).
Fig.1a gives an example of a battery tube cathode suspension with a low filament current, i.e. having a very thin wire, while Fig.1b refers to a direct-glow rectifying tube in which a nickel tape covered with an active oxide layer is used. Such a tube generally has a relatively high emission. Pure tungsten wires without an active layer are not used in currently manufactured types of receiver tubes.