The SCR-54 was a tunable, portable crystal radio receiver used by the U. S. Army during World War I for fire control in conjunction with airplanes.
The SCR-54 was a tunable, portable crystal radio receiver used by the U. S. Army during World War I for fire control in conjunction with airplanes.
French radio equipment was more advanced than that of the U. S. Army when the United States entered World War I. The U. S. Army therefore adopted French sets early on, and developed improved sets of their own, some based on French design. Several of the French A-1 artillery receiving set were sent to the American radio laboratory in the summer of 1917 and copied with minor modifications. It was first released as the AR-4 in limited numbers for field tests, supervised by Captain Edwin Armstrong. [1] Several changes were made based on his suggestions. The receiver was redesigned and reissued as the SCR-54 (Set, Complete, Radio). Since there was high demand, several companies produced these sets or components, including DeForest Radio Telephone and Telegraph, Liberty Electric, Wireless Specialty Apparatus, Marconi, and General Radio.
Its primary (antenna) and secondary circuits were both tunable by variable capacitance and inductance. A crystal detector (Type DC-1) and telephone circuit were connected to the secondary circuit. It could receive wavelengths from 250–550 meters (545 to 1200 kHz). The receiver included two crystal (galena) [2] detectors, one sealed in glass, and the other not, which were attached on the surface of the receiver. A buzzer circuit, powered by a BA-4 battery, was mounted in the box cover and used to adjust the crystal.
The set was compact and mounted in a wooden box, type BC-14. The lid of the box held the buzzer circuit, detectors, a screwdriver, two P-11 telephone headsets, spare parts, extra crystals, and an operating manual, “Radio Pamphlet No. 3”. [2]
The receiver was intended to be used with antenna type A-2 or A-2-B.
There was an optional vacuum tube detector, type DT-3-A, available for the SCR-54. It used a VT-1 vacuum tube powered by a BA-2 battery. The type number was originally SCR-55, later changed to DT-3, then DT-3-A. The crystal proved more popular in field use. [3]
The SCR-54-A featured electrical and mechanical improvements over the SCR-54. Most notably, the buzzer circuit was removed from the lid and incorporated into the chassis of the receiver proper.
The SCR-54 was intended to be used at artillery stations to receive messages from fire control aircraft. Many were produced but relatively few reached the field before the war ended. Some were retained by the Signal Corps, but the bulk, most never used, were sold as surplus to the public, becoming a favorite of amateurs.
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF bands. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz. In all cases, microwaves include the entire SHF band at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.
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A crystal radio receiver, also called a crystal set, is a simple radio receiver, popular in the early days of radio. It uses only the power of the received radio signal to produce sound, needing no external power. It is named for its most important component, a crystal detector, originally made from a piece of crystalline mineral such as galena. This component is now called a diode.
The Audion was an electronic detecting or amplifying vacuum tube invented by American electrical engineer Lee de Forest in 1906. It was the first triode, consisting of an evacuated glass tube containing three electrodes: a heated filament, a grid, and a plate. It is important in the history of technology because it was the first widely used electronic device which could amplify. A low power signal at the grid could control much more power in the plate circuit.
A regenerative circuit is an amplifier circuit that employs positive feedback. Some of the output of the amplifying device is applied back to its input so as to add to the input signal, increasing the amplification. One example is the Schmitt trigger, but the most common use of the term is in RF amplifiers, and especially regenerative receivers, to greatly increase the gain of a single amplifier stage.
A tuned radio frequency receiver is a type of radio receiver that is composed of one or more tuned radio frequency (RF) amplifier stages followed by a detector (demodulator) circuit to extract the audio signal and usually an audio frequency amplifier. This type of receiver was popular in the 1920s. Early examples could be tedious to operate because when tuning in a station each stage had to be individually adjusted to the station's frequency, but later models had ganged tuning, the tuning mechanisms of all stages being linked together, and operated by just one control knob. By the mid 1930s, it was replaced by the superheterodyne receiver patented by Edwin Armstrong.
In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. The antenna intercepts radio waves and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information. The receiver uses electronic filters to separate the desired radio frequency signal from all the other signals picked up by the antenna, an electronic amplifier to increase the power of the signal for further processing, and finally recovers the desired information through demodulation.
An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not to be confused with electrical elements, which are conceptual abstractions representing idealized electronic components and elements.
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A crystal detector is an obsolete electronic component used in some early 20th century radio receivers that consists of a piece of crystalline mineral which rectifies the alternating current radio signal. It was employed as a detector (demodulator) to extract the audio modulation signal from the modulated carrier, to produce the sound in the earphones. It was the first type of semiconductor diode, and one of the first semiconductor electronic devices. The most common type was the so-called cat whisker detector, which consisted of a piece of crystalline mineral, usually galena, with a fine wire touching its surface.
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