Category: Radioamator - Contents
Radioamator, październik 1950r., rok I, numer 10
(Radio amateur, October 1950, volume I, number 10)
Diagrams of receivers types: Nora W.16 Tosca and Nora GW. 16 Tosca (cover page 2)
The diagrams below show connections in receivers manufactured by 'Nora' of the "Tosca" "W16" and "GW16" types. Both receivers are two-tube with a third rectifier, two-range (medium and long waves) and belong to the category of simple devices. They have the same receiving frequency, but they differ in the method of supplying electricity and the types of tubes. The "Tosca" "W16" receiver is powered by alternating current from the lighting network and has the first AF7 type tube that acts as a detector. The second - is a loudspeaker type AL4 The AZ1 rectifying tube works in an anode power supply.
The "Tosca" "GW16" receiver can be supplied with alternating or direct current from the lighting network. It has receiver tubes that correspond to the types of electric tubes in the first camera, i.e. detector - CF7 and speaker - CL4. The power supply uses a CY1 rectifying electron tube and the "Urdox" U920 current regulator.
Both devices have volume control and selectivity control, which is achieved by changing the capacitance of the differential capacitor located in the antenna circuit. They also have built-in eliminators, which allow for clear reception of foreign stations, undisturbed by local radio broadcasts. The timbre of the sound is regulated by switching on and off the appropriate permanent capacitor located in the anode circuit of the loudspeaker tube. Both devices have identical boxes.
Soviet television (1)
In 1922, when a radio broadcasting station in New York had a power of less than 1.5 kW, a 12 kW transmitter was built and put into operation in the Soviet Union. In the same year 1922, the Soviet Union took the first place in the world in terms of the power of transmitting stations, ahead of other countries' radio technology, which often drew on the experience of Soviet engineers. For example, in the words of the Americans themselves, the Soviet system for building super-powerful transmitters was used to build a 500 kW station near Cincinati. A modulation system developed in the USSR was also used in the New York TV transmitter.
Excellent results were achieved in the Soviet Union and in the field of television.
The theoretical foundations of television were prepared in 1888 - 1890 by many Russian scientist, physicist A.G. Stoletov, who studied the effect of light on the electrical conductivity of gases and constructed the world's first photoelement.
The rise of the technical and economic power of the Soviet Union, the achievements of Soviet science created the conditions for a jump in the development of Soviet television from the standard of 343 lines to 625 lines, which was ahead of Europe (405) and America (525 lines).
The transition of the Moscow TV station to a new standard was connected not only with increasing the clarity of the image, but also with the expansion and increased power of the devices.
The task of significantly increasing the technical and operational capabilities of television was completed with full success.
Soviet readers were surprised to read in a magazine from an English news outlet in the USSR recently that England still used the pre-war standard on television and that it was considered "completely satisfactory"...
Let's learn radio technology - Cathodes (3)
The cathode of the electron tube, in order to work normally, that is, to emit free electrons to the outside, must be heated to a certain strictly defined temperature. The cathodes of the tubes are heated by electric, direct or alternating current, the "direct filament" tubes are designed rather for direct current operation, while the "indirect filament" tubes may be heated freely, using direct or alternating current. The electric power of the filament current lost as heat in the cathode is calculated by multiplying the filament voltage in volts by the filament current in amperes. For example, if we have a 4 volt electron tube whose filament current is 1 ampere, then the filament power is: 4 x 1 = 4 watts. Filament is needed in order to keep the cathode temperature constant. As the hot cathode radiates heat to the outside and thus cools down, it is still necessary to supplement these deficiencies by supplying electricity from the filament source..
The power needed to heat the cathode in the electron tube depends on the surface of the cathode and the temperature at which it works. The least amount of glow power is required for electron tubes with an oxide cathode because, as we know, the operating temperature of the oxide cathodes is not high. The cathode area determines the amount of electron emission. High-emission electron tubes require large-area cathodes, which entails high filament power. Electron tubes with low emission have a small area and therefore the required filament power is small. Knowing the glow power of the electron tube, we can approximately determine its maximum emission. For one watt of power lost in the cathode, as we know, in the case of the oxide cathode, we can count about 100 mA of emission, so in the case of an electron tube with a filament power of 4 W, the maximum emission current will be in the order of 400 mA.
Tubes with the same filament voltage are connected in parallel to the power source, similar to e.g. electric bulbs for the lighting network.
Parallel connection of electron tubes is used in alternating current battery and mains devices - generally with low-voltage electron tubes.
On the other hand, in DC or universal apparatus, i.e. DC and AC, all filament filaments are connected in series. Since in this case the same current flows through all the tubes, all tubes used in such a system must be built for the same filament current.
However, in individual cases, instead of e.g. one 100 mA tube, two parallel connected 50 milliampere tubes may be connected to the power supply circuit. The power supply of tubes connected in series with each other must be at a nominal current. If the sum of the voltages of all serially connected tubes is lower than the voltage of the supplying source, then we have to connect the resistance in series with the tubes and adjust the current to the nominal value. Instead of a constant resistance of an appropriate value, an iron-hydrogen resistance called "Urdox" is usually used, which works automatically, i.e. it adjusts the filament current to the appropriate nominal value regardless of the voltage supply.
Now that we know the properties of the cathodes, let's get acquainted with the leads of the electron tubes and see what terminals the filament filament ends are connected to..
Read more: Radioamator (Radio amateur) 1950/10