The tubes.

From the book 'Vacuum Tubes in Wireless Communication' by Elmer E. Bucher. Published in 1919.

Weagant oscillation valve.

During the period 1913-1914, R Weagant, Chief Engineer of the Marconi Wireless Telegraph Company of America, devised a three-electrode valve of a novel type. The prominent characteristics of the tube are its simplicity of construction with consequent cheapness of manufacture, stability and efficiency.

The inventor found that the third electrode for control of the electron currents between the filament and plate, need not be placed inside the bulb. If correctly mounted on the outside of the bulb, the valve functions as well as the bulb with the internal "grid", whether used as detector, amplifier or an oscillating generator.

Experimental type of Weagant's oscillation valve.

Weagant four-element valve.

The four-element valve differs from the three-element tube in that it has an unconnected grid element G placed between filament F and plate P. The sensitiveness of the tube, as an oscillation detector, is thereby improved. External to the glass container and parallel with the internal electron stream is placed the electrostatic control element K which is generally connected to the high potential terminal of the secondary of the receiving transformer. The immediate effect of inserting the element G is to give the tube a more favourable characteristic for the detection of radio frequency currents.

Weagant transmitting tube.

Along with the production of the three-element oscillation valve, Mr. Weagant and his staff have developed the transmitting tube shown. The figure at the right shows the support and construction of the plate, and the filament which is in the form of a ring. The elements are contained in a Pyrex glass tube and appropriate caps are placed on either end of the tube for support and external connection. The valve is approximately 1 7/8" in diameter, 6 1/2" long, in which is placed a disc plate 1 1/4" in diameter and a filament of approximately the same diameter supported at the opposite end.

Kenotron and Pliotron.

Irving Langmuir and Saul Dushman, together with Mr. William C. White, have described in various publications the two-electrode and three-electrode vacuum valve tubes, which they have been instrumental in developing. These are simply extensions of Fleming's original disclosures. These tubes are exhausted to an exceedingly high vacuum by an elaborate process.

The two-electrode valve called the "Kenotron" is employed principally as a rectifier of high voltage alternating currents, but obviously, small bulbs might be employed as oscillation detectors for the reception of wireless telegrams. With a plate potential as low as 200 volts electron currents up to one ampere have been secured with these tubes, but, as pointed out by Langmuir, a more serviceable tube is one designed for electron currents of 250 mill amperes. If a greater current is desired, several "Kenotrons" may be operated in parallel. The "Kenotron" tubes have been employed to rectify alternating currents up to 180,000 volts. For any purpose for which high voltage direct current is desirable, they have proven practical and serviceable.

In the three-electrode tube, the "Pliotron", the grid is shown at G, the filament at F - which is supported by a glass frame - and the plate or anode at A. The grid consist of a number of turns of tungsten wire .01 millimetre in diameter, spaced to include 100 turns to the centimetre. The filament is mounted inside the grid. The plates or anodes on either side of the filament consist of tungsten wire wound zigzag in the manner shown.

A large "Pliotron" which may be termed a "power" bulb. A tube of these dimensions may be employed to generate several watts of radio frequency alternating current from a source of direct current. Hundreds of bulbs may be connected in parallel for the production of radio frequency currents at very large powers.

A commonly used type.

A commonly used type of a three-electrode valve as an oscillation detector. The material of the grid, plate and filament being as follows: the filament is made of lime coated platinum and is energized by a 4 to 6 volt battery; the grid is composed of a number of turns of tungsten wire spaced equally on either side of the filament. The plates are made of sheet nickel ½" by 1" placed on either side of the grid. The voltage of the plate circuit varies from 90 to 150 volts or more.

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