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Nuvistor 530
The nuvistor is a type of vacuum tube announced by RCA in 1959. Nuvistors were made to compete with the then-new bipolar junction transistors, and were much smaller than conventional tubes of the day, almost approaching the compactness of early discrete transistor casings. Due to their small size, there was no space to include a vacuum fitting to evacuate the tube; instead, nuvistors were assembled and processed in a vacuum chamber with simple robotic devices. The tube is made entirely of metal with a ceramic base. Triodes and a few tetrodes were made; Nuvistor tetrodes were taller than their triode counterparts. Nuvistors are among the highest performing small signal receiving tubes. They feature excellent VHF and UHF performance plus low noise figures, and were widely used throughout the 1960s in television sets (beginning with RCA's "New Vista" line of color sets in 1961 with the CTC-11 chassis), radio and high-fidelity equipment primarily in RF sections, and oscilloscope ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wire
Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm A wire is a flexible strand of metal. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Wire gauges come in various standard sizes, as expressed in terms of a gauge number. Wires are used to bear mechanical loads, often in the form of wire rope. In electricity and telecommunications signals, a "wire" can refer to an electrical cable, which can contain a "solid core" of a single wire or separate strands in stranded or braided forms. Usually cylindrical in geometry, wire can also be made in square, hexagonal, flattened rectangular, or other cross-sections, either for decorative purposes, or for technical purposes such as high-efficiency voice coils in loudspeakers. Edge-wound coil springs, such as the Slinky toy, are made of special flatten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isolated as a metal in 1783. Its important ores include scheelite and wolframite, the latter lending the element its alternate name. The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all known elements barring carbon (which sublimes at normal pressure), melting at . It also has the highest boiling point, at . Its density is , comparable with that of uranium and gold, and much higher (about 1.7 times) than that of lead. Polycrystalline tungsten is an intrinsically brittle and hard material (under standard conditions, when uncombined), making it difficult to work. However, pure single-crystalline tungsten is more ductile and can be cut with a hard-steel hacksaw. Tungsten occurs in many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hot Cathode
In vacuum tubes and gas-filled tubes, a hot cathode or thermionic cathode is a cathode electrode which is heated to make it emit electrons due to thermionic emission. This is in contrast to a cold cathode, which does not have a heating element. The heating element is usually an electrical filament heated by a separate electric current passing through it. Hot cathodes typically achieve much higher power density than cold cathodes, emitting significantly more electrons from the same surface area. Cold cathodes rely on field electron emission or secondary electron emission from positive ion bombardment, and do not require heating. There are two types of hot cathode. In a ''directly heated cathode'', the filament is the cathode and emits the electrons. In an ''indirectly heated cathode'', the filament or ''heater'' heats a separate metal cathode electrode which emits the electrons. From the 1920s to the 1960s, a wide variety of electronic devices used hot-cathode vacuum tubes. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in which positive charges move. Electrons have a negative electrical charge, so the movement of electrons is opposite to that of the conventional current flow. Consequently, the mnemonic ''cathode current departs'' also means that electrons flow ''into'' the device's cathode from the external circuit. For example, the end of a household battery marked with a + (plus) is the cathode. The electrode through which conventional current flows the other way, into the device, is termed an anode. Charge flow Conventional current flows from cathode to anode outside of the cell or device (with electrons moving in the opposite direction), regardless of the cell or device type and operating mode. Cathode polarity with respect to the anode can be positive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Control Grid
The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode, used to control the flow of electrons from the cathode to the anode (plate) electrode. The control grid usually consists of a cylindrical screen or helix of fine wire surrounding the cathode, and is surrounded in turn by the anode. The control grid was invented by Lee De Forest, who in 1906 added a grid to the Fleming valve (thermionic diode) to create the first amplifying vacuum tube, the Audion (triode). Operation In a valve, the hot cathode emits negatively charged electrons, which are attracted to and captured by the anode, which is given a positive voltage by a power supply. The control grid between the cathode and anode functions as a "gate" to control the current of electrons reaching the anode. A more negative voltage on the grid will repel the electrons back toward the cathode so fewer get through to the anode. A less negative, or positive, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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