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Preselector
A preselector is a name for an electronic device that connects between a radio antenna and a radio receiver. The preselector is a band-pass filter that blocks troublesome out-of-tune frequencies from passing through from the antenna into the radio receiver (or preamplifier) that otherwise would be directly connected to the antenna. Purpose A preselector improves the performance of nearly any receiver, but is especially helpful to receivers with broadband front-ends that are prone to overload, such as scanners, wideband software-defined radio receivers, ordinary consumer-market shortwave and AM broadcast receivers – particularly with receivers operating below 10~20 MHz where static is pervasive. Sometimes faint signals that occupy a very narrow frequency span (such as radiotelegraph or 'CW') can be heard more clearly if the receiving bandwidth is made narrower than the narrowest that a general-purpose receiver may be able to tune; likewise, signals which i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Noise
In radio reception, radio noise (commonly referred to as radio static) is unwanted random radio frequency electrical signals, fluctuating voltages, always present in a radio receiver in addition to the desired radio signal. Radio noise is a combination of natural electromagnetic atmospheric noise ("spherics", static) created by electrical processes in the atmosphere like lightning; human-made radio frequency interference () from other electrical devices picked up by the receiver's antenna (radio), antenna; and thermal noise present in the receiver input circuits, mostly caused by the random thermal motion of molecules inside resistors. Effects of noise on radio Radio noise near in frequency to a received radio signal (in the receiver's passband) radio frequency interference, interferes (radio frequency interference, ) with the operation of the receiver's circuitry. The level of noise determines the maximum sensitivity and reception range of a radio receiver; if no noise were pi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clipping (audio)
Clipping is a form of waveform distortion that occurs when an amplifier is overdriven and attempts to deliver an output voltage or current beyond its maximum capability. Driving an amplifier into clipping may cause it to output power in excess of its power rating. In the frequency domain, clipping produces strong harmonics in the high-frequency range (as the clipped waveform comes closer to a square wave). The extra high-frequency weighting of the signal could make tweeter damage more likely than if the signal was not clipped. In most cases, the distortion associated with clipping is unwanted, and is visible on an oscilloscope even if it is inaudible. However, clipping is often used in music for artistic effect, particularly guitar-dominant genres like blues, rock, and metal. Overview When an amplifier is pushed to create a signal with more power than its power supply can produce, it will amplify the signal only up to its maximum capacity, at which point the signal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clipping (signal Processing)
Clipping is a form of distortion that limits a signal once it exceeds a threshold. Clipping may occur when a signal is recorded by a sensor that has constraints on the range of data it can measure, it can occur when a signal is digitized, or it can occur any other time an analog or digital signal is transformed, particularly in the presence of gain or overshoot and undershoot. Clipping may be described as hard, in cases where the signal is strictly limited at the threshold, producing a flat cutoff; or it may be described as soft, in cases where the clipped signal continues to follow the original at a reduced gain. Hard clipping results in many high-frequency harmonics; soft clipping results in fewer higher-order harmonics and intermodulation distortion components. Audio In the frequency domain, clipping produces strong harmonics in the high-frequency range (as the clipped waveform comes closer to a square wave). The extra high-frequency weighting of the signal could ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timbre
In music, timbre (), also known as tone color or tone quality (from psychoacoustics), is the perceived sound of a musical note, sound or tone. Timbre distinguishes sounds according to their source, such as choir voices and musical instruments. It also enables listeners to distinguish instruments in the same category (e.g., an oboe and a clarinet, both woodwinds). In simple terms, timbre is what makes a particular musical instrument or human voice have a different sound from another, even when they play or sing the same note. For instance, it is the difference in sound between a guitar and a piano playing the same note at the same volume. Both instruments can sound equally tuned in relation to each other as they play the same note, and while playing at the same amplitude level each instrument will still sound distinctive with its own unique tone color. Musicians distinguish instruments based on their varied timbres, even instruments playing notes at the same pitch and volume ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplitude Distortion
Amplitude distortion is distortion occurring in a system, subsystem, or device when the output amplitude is not a linear function of the input amplitude under specified conditions. Generally, output is a linear function of input only for a fixed portion of the transfer characteristics. In this region, Ic=βIb where Ic is collector current and Ib is base current, following linear relation y=mx. When output is not in this portion, two forms of amplitude distortion might arise # Harmonic distortion : The creation of harmonics of the fundamental frequency of a sine wave input to a system. # Intermodulation distortion : This form of distortion occurs when two sine waves of frequencies ''X'' and ''Y'' are present at the input, resulting in the creation of several other frequency components, whose frequencies include (X+Y), (X-Y), (2X-Y), (2Y-X), and generally (mX ± nY) for integer m and n. Generally the size of the unwanted output falls rapidly as m and n increase. Due to the additio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplifier Figures Of Merit
In electronics, the figures of merit of an amplifier are numerical measures that characterize its properties and performance. Figures of merit can be given as a list of specifications that include properties such as gain, bandwidth, noise and linearity, among others listed in this article. Figures of merit are important for determining the suitability of a particular amplifier for an intended use. Gain The gain of an amplifier is the ratio of output to input power or amplitude, and is usually measured in decibels. When measured in decibels it is logarithmically related to the power ratio: ''G''(dB)=10 log(''Pout'' /''Pin''). RF amplifiers are often specified in terms of the maximum ''power gain'' obtainable, while the voltage gain of audio amplifiers and instrumentation amplifiers will be more often specified. For example, an audio amplifier with a gain given as 20 dB will have a ''voltage gain'' of ten. The use of voltage gain figure is appropriate when the amplifier's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Range
Dynamics (from Greek δυναμικός ''dynamikos'' "powerful", from δύναμις ''dynamis'' " power") or dynamic may refer to: Physics and engineering * Dynamics (mechanics), the study of forces and their effect on motion Brands and enterprises * Dynamic (record label), an Italian record label in Genoa Mathematics * Dynamical system, a concept describing a point's time dependency ** Topological dynamics, the study of dynamical systems from the viewpoint of general topology * Symbolic dynamics, a method to model dynamical systems Social science * Group dynamics, the study of social group processes especially * Population dynamics, in life sciences, the changes in the composition of a population * Psychodynamics, the study of psychological forces driving human behavior * Social dynamics, the ability of a society to react to changes * Spiral Dynamics, a social development theory Other uses * Dynamics (music), the softness or loudness of a sound or note * DTA Dynami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RF Power Amplifier
A radio-frequency power amplifier (RF power amplifier) is a type of electronic amplifier that converts a low-power radio-frequency (RF) signal into a higher-power signal. Typically, RF power amplifiers are used in the final stage of a radio transmitter, their output driving the antenna. Design goals often include gain, power output, bandwidth, power efficiency, linearity (low signal compression at rated output), input and output impedance matching, and heat dissipation. Amplifier classes The operation of RF amplifier circuits is classified based on the proportion of the cycle of the sinusoidal radio signal the amplifier (transistor or vacuum tube) where current is conducting. Class-A, class-AB and class-B are considered the linear amplifier classes in which the active device is used as a controlled current source, while class-C is a nonlinear class in which the active device is used as a switch. The bias at the input of the active device determines the class of the ampl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Response Curves For A Radio Receiver Preselector
Response may refer to: *Call and response (music), musical structure *Reaction (other) *Request–response **Output or response, the result of telecommunications input *Response (liturgy), a line answering a versicle * Response (music) or antiphon, a response to a psalm or other part of a religious service *Response, a phase in emergency management *Response rate (survey) Proper names and titles *''Response'', a print and online magazine of Christian thought published by Seattle Pacific University * ''Response'' (album), a studio album by Phil Wickham *Response (company), a call centre company based in Scotland * ''The Response'' (film) *The National War Memorial (Canada), titled ''The Response'' *The Northumberland Fusiliers Memorial in Newcastle upon Tyne, titled "The Response" See also *Action (other) *Answer (other) *Reply (other) *Response variable, or the realization thereof *Responsions, an examination formerly required for a degree at O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interference (wave Propagation)
In physics, interference is a phenomenon in which two coherent waves are combined by adding their intensities or displacements with due consideration for their phase difference. The resultant wave may have greater amplitude (constructive interference) or lower amplitude (destructive interference) if the two waves are in phase or out of phase, respectively. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, surface water waves, gravity waves, or matter waves as well as in loudspeakers as electrical waves. Etymology The word ''interference'' is derived from the Latin words ''inter'' which means "between" and ''fere'' which means "hit or strike", and was used in the context of wave superposition by Thomas Young in 1801. Mechanisms The principle of superposition of waves states that when two or more propagating waves of the same type are incident on the same point, the resultant amplitude at that point is equal to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bandwidth (signal Processing)
Bandwidth is the difference between the upper and lower Frequency, frequencies in a continuous Frequency band, band of frequencies. It is typically measured in unit of measurement, unit of hertz (symbol Hz). It may refer more specifically to two subcategories: ''Passband bandwidth'' is the difference between the upper and lower cutoff frequencies of, for example, a band-pass filter, a communication channel, or a signal spectrum. ''Baseband bandwidth'' is equal to the upper cutoff frequency of a low-pass filter or baseband signal, which includes a zero frequency. Bandwidth in hertz is a central concept in many fields, including electronics, information theory, digital communications, radio communications, signal processing, and spectroscopy and is one of the determinants of the capacity of a given communication channel. A key characteristic of bandwidth is that any band of a given width can carry the same amount of information, regardless of where that band is located in the f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
