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.
A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency. It was invented by French radio engineer and radio manufacturer Lucien Lévy. Virtually all modern radio receivers use the superheterodyne principle.
In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna with the purpose of signal transmission up to a radio receiver. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves.
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 as a diode in 1906. Improved, it was patented as the first triode in 1908, 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 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 electronic device or physical entity part of 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. A datasheet for an electronic component is a technical document that provides detailed information about the component's specifications, characteristics, and performance. Discrete circuits are made of individual electronic components that only perform one function each as packaged, which are known as discrete components, although strictly the term discrete component refers to such a component with semiconductor material such as individual transistors.
In electronics, a local oscillator (LO) is an electronic oscillator used with a mixer to change the frequency of a signal. This frequency conversion process, also called heterodyning, produces the sum and difference frequencies from the frequency of the local oscillator and frequency of the input signal. Processing a signal at a fixed frequency gives a radio receiver improved performance. In many receivers, the function of local oscillator and mixer is combined in one stage called a "converter" - this reduces the space, cost, and power consumption by combining both functions into one active device.
A crystal detector is a type of electronic component used in some early 20th century radio receivers. It consists of a piece of crystalline mineral that rectifies an 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's whisker detector, which consisted of a piece of crystalline mineral, usually galena, with a fine wire touching its surface.
The AN/ARC-5 Command Radio Set is a series of radio receivers, transmitters, and accessories carried aboard U.S. Navy aircraft during World War II and for some years afterward. It is described as "a complete multi-channel radio transmitting and receiving set providing communication and navigation facilities for aircraft. The LF-MF-HF components are designed to transmit and receive voice, tone-modulated, and continuous wave (cw) signals." Its flexible design provided AM radiotelephone voice communication and Modulated continuous wave (MCW) and Continuous wave (CW) Morse code modes, all of which are typical capabilities in other Navy aircraft communication sets of the period. It was an improvement of the Navy's ARA/ATA command set. Similar units designated SCR-274-N were used in U.S. Army aircraft. The Army set is based on the ARA/ATA, not the later AN/ARC-5. The ARA/ATA and SCR-274-N series are informally referred to as "ARC-5", despite small differences that render all three series incompatible. Like the AN/ARC-5, the ARA/ATA and SCR-274-N had AM voice communication and two-way MCW and CW Morse code capability.
The autodyne circuit was an improvement to radio signal amplification using the De Forest Audion vacuum tube amplifier. By allowing the tube to oscillate at a frequency slightly different from the desired signal, the sensitivity over other receivers was greatly improved. The autodyne circuit was invented by Edwin Howard Armstrong of Columbia University, New York, NY. He inserted a tuned circuit in the output circuit of the Audion vacuum tube amplifier. By adjusting the tuning of this tuned circuit, Armstrong was able to dramatically increase the gain of the Audion amplifier. Further increase in tuning resulted in the Audion amplifier reaching self-oscillation.
The SCR-536 was a hand-held radio transceiver used by the US Army Signal Corps in World War II. It is popularly referred to as a walkie talkie, although it was originally designated a "handie talkie".
The SCR-300, designated AN/VRC-3 under the Joint Electronics Type Designation System, was a portable radio transceiver used by US Signal Corps in World War II. This backpack-mounted unit was the first radio to be nicknamed a "walkie talkie".
The AN/MRN-1 was an instrument approach localizer used by the Army Air Force during and after World War II. It was standardized on 3 July 1942. It replaced the SCR-241, and was a component of SCS-51.
The SCR-108 Radio Truck was a Signal Corps Radio vehicle used by the United States Army during and after World War I for short range air-to-ground communications,
The Radio tractor was a mobile Signal Corps Radio used by the U.S. Army for ground communications before and during World War I. Prior to World War I, trucks were referred to as "tractors", and there were also telegraph tractors, and telephone tractors.
The SCR-245 Radio was a mobile MF/HF Signal Corps Radio used by the U.S. Army before and during World War II, for short range ground communications, It was one of the first crystal controlled sets used by the Army.
The SCR-508 radio was a mobile Signal Corps Radio used by the U.S. Army during World War II, for short range ground communications. The SCR-508 series radio represented the Army's commitment to both FM and crystal tuning, and was used extensively by armor and mechanized units. The turret bustle of late series light and medium tanks was designed around this radio.
Radio waves were first identified in German physicist Heinrich Hertz's 1887 series of experiments to prove James Clerk Maxwell's electromagnetic theory. Hertz used spark-excited dipole antennas to generate the waves and micrometer spark gaps attached to dipole and loop antennas to detect them. These precursor radio receivers were primitive devices, more accurately described as radio wave "sensors" or "detectors", as they could only receive radio waves within about 100 feet of the transmitter, and were not used for communication but instead as laboratory instruments in scientific experiments and engineering demonstrations.