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NOTE: This article is currently being extensively rewritten and expanded off line. Any edits made between now and when the rewritten article is uploaded will probably be lost.
The pentagrid converter was a radio receiving valve (vacuum tube) with five grids used in the frequency-converter (mixer) stage of a superheterodyne radio receiver. In electronics, a vacuum tube (U.S. and Canadian English) or (thermionic) valve (outside North America) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. ...
The Super Heterodyne receiver (or to give it its full name, The Supersonic Heterodyne Receiver) was invented by Edwin Armstrong in 1918. ...
A Pentagrid converter is a valve that is able to act as both a Local oscillator and also to mix the incoming signal to produce an intermediate frequency The oscillator was able to operate independently because one of the grids (grid 2) was connected into what would normally be the oscillator's anode (plate) circuit. Screen Grids were placed to separate the action of the Mixer section from the oscillator section. The output of the oscillator was electron coupled to the actual mixer. The makers described this as a vitual cathode. The RF signal was fed into the tube by Grid 4. The action of that grid on the electron stream that already was varing at the local ocsillator frequency produced the Sum and difference frequencies. The Superheterodyne receiver (or to give it its full name, The Supersonic Heterodyne Receiver – usually these days shortened to superhet) was invented by Edwin Armstrong in 1918. ...
An intermediate frequency (IF) is a frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception. ...
The resulting difference at the IF frequency was available in the converter's anode (plate) circuit, and was coupled, with a circuit tuned to the intermedate frequency, to the rest of the radio. Diagram of a zinc anode in a Daniells cell. ...
Plate has several meanings: A plate electrode in a vacuum tube. ...
In North America the All American Five radio was found in every home, and usually used a pentagrid converter. The types were typically, in chronological order, the 2A7 (1934), 6A7, 6A8 (metal- 1935), the 12SA7 (1939)Single ended for series strings, and the 12BE6 miniature (1945). 6SA7 and 6BE6 versions were also available for radios with power transformers, and car radios for cars with 6 volt electrical systems. In the late 1950s, pentagrid conveter tubes like the 12AD6 were introduced designed to operate with 12 Volts on the plate for hybrid car radios. World map showing North America A satellite composite image of North America. ...
The All American Five was a superheterodyne radio receiver designed in the USA in the 1930s and using five vacuum tubes. ...
1934 (MCMXXXIV) was a common year starting on Monday (link will take you to calendar). ...
1935 (MCMXXXV) was a common year starting on Tuesday (link will take you to calendar). ...
The All American Five was a superheterodyne radio receiver designed in the USA in the 1930s and using five vacuum tubes. ...
1939 (MCMXXXIX) was a common year starting on Sunday (link will take you to calendar). ...
The All American Five was a superheterodyne radio receiver designed in the USA in the 1930s and using five vacuum tubes. ...
1945 (MCMXLV) was a common year starting on Monday (the link is to a full 1945 calendar). ...
During the valve (tube) era of radio, frequency conversion in superheterodyne receivers was typcally carried out in British and European sets by a hexode thermionic valve (tube), energised with the incoming signal, plus the local oscillator signal derived from an additional triode valve (tube). Both valves (tubes) would typically be contained within a single envelope and was known as a Hexode-Triode Converter (such as the ECH35). The Americans seldom used that method, even though the 6K8, 1938 was available. In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify a signal. ...
The Superheterodyne receiver (or to give it its full name, The Supersonic Heterodyne Receiver – usually these days shortened to superhet) was invented by Edwin Armstrong in 1918. ...
Simplified diagram of a triode. ...
1938 (MCMXXXVIII) was a common year starting on Saturday (link will take you to calendar). ...
The design of receivers in Britain was largely controlled by the British Valve Association. Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ...
Unless suitable filtering in the RF circuit was provided, it was quite possible for the local oscillator signal to be radiated from the aerial (antenna). Inexpensive sets may not have provided a tuned stage in the antena circuit which allowed the radio to cause interference. The American Federal Communications Commission started requiring that radio manufactuers certify their products were built to avoid such interference under Part 15 of the FCC rules. A yagi antenna Most simply, an antenna is an electronic component designed to send or receive radio waves. ...
A yagi antenna Most simply, an antenna is an electronic component designed to send or receive radio waves. ...
The abbreviation FCC can refer to: Face-centered cubic (usually fcc), a crystallographic structure Federal Communications Commission, a US government organization Farm Credit Corporation/Farm Credit Canada, a Canadian government organization Families with Children from China, an adoption support organization Florida Christian College, a college in central Florida Fresno City...
The Pentagrid converter was commonly used on the Standard Broadcast band, although many shortwave radios managed quite satifactory operation with the same tubes. Special High frequency versions like the 6SB7Y (1946) and 6BA7 (1948) managed good results at 100 MHz in receivers for the Post World War II FM broadcast band of 88-108 MHz. The Zenith Trans-Oceanic portable shortwave radio used the 1L6 in the later models, and the loctal 1LA6 on earlier models. 1946 (MCMXLVI) was a common year starting on Tuesday. ...
1948 (MCMXLVIII) was a leap year starting on Thursday (the link is to a full 1948 calendar). ...
The Trans-Oceanic was the name given to a series of portable radios produced from 1942 to 1962 by Zenith Radio. ...
The 1L6 is a 7 pin miniature vacuum tube of the pentagrid converter type. ...
Note: that although this valve (tube) contains 7 electrodes and is thus technically a heptode, this device is usually referred to in technical literature as a pentagrid, to distinguish it from a true heptode. The grid that carries the input signal has to have a screen grid on either side to isolate it from the oscillator grid. The remaining grid is the suppressor grid to combat secondary emission. A grid introduced into a thermionic valve or tube to greatly reduce the capacitance between two other parts of the electrode structure. ...
A grid used in a thermionic valve (also called vacuum tube) to suppress secondary emission. ...
Secondary emission is a phenomenon that occurs in electron tubes where electrons impact an electrode with sufficient energy to knock additional electrons from the surface of that electrode. ...
History
The tube was invented by Donald G. Haines of RCA. His patent was 2,148,266, filed 3-28-33 but not granted until 3-29-39. The tube was promoted via RCA App. Note No. 3, "Use and Operation of the 2A7 and 6A7 as Frequency Converters," dated 3-24-33. The Final RMA registration was not granted until 11-22-34. As John Stokes says in 70 years of Radio Tubes, "Although this tube as not strictly the first in which the functions of oscillator and mixer had been combined - the French bi-grille tubes had earned that distinction - it was the first to achieve so called 'mulitiplative mixing."
The history of all forms of freq. converters is covered in detail in Keith Thrower's "History of the British Radio Valve to 1940." He says the first British commercial pentagrid converter / heptode was the Ferranti VHT4, appearing late in 1933. However, he cites a 1932 British patent application by E. Yeoman Robinson of Edison-Swan, covering hexodes, heptodes, octodes, and triode-hexodes. (Brit. Patent 408,203, applied for 7-4-32 and 3-7-33, granted 4-4-34.)
The only Octode produced in the USA was the Sylvania 7A8 1939 1939 (MCMXXXIX) was a common year starting on Sunday (link will take you to calendar). ...
The pentagrid Converter was well Known in Europe. UK patent GB426802 shows a method of using an Octode which the patent calls a Pentagrid as a combined converter and reflex IF amplifier.
External links
References Sibley, Ludwell, "Tube Lore", 1996
Stokes, john W, "70 Years of Radio Tubes and Valves" 1997
Thrower, Keith, "History of the British Radio Valve to 1940."
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