A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration. In Telecommunications, modulation is the process of varying a periodic Waveform, i In Telecommunications, modulation is the process of varying a periodic Waveform, i Amplitude modulation ( AM) is a technique used in electronic communication most commonly for transmitting information via a Radio Carrier wave Single-sideband modulation ( SSB) is a refinement of Amplitude modulation that more efficiently uses electrical power and bandwidth. Phase modulation (PM is a form of Modulation that represents information as variations in the instantaneous phase of a Carrier wave. Space modulation is a radio Amplitude Modulation technique used in Instrument Landing Systems that incorporates the use of multiple antennas fed with various radio In Telecommunications, modulation is the process of varying a periodic Waveform, i On-off keying ( OOK) is a type of Modulation that represents Digital Data as the presence or absence of a Carrier wave. Frequency-shift keying (FSK is a Frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a Carrier wave Amplitude-shift keying ( ASK) is a form of Modulation that represents Digital Data as variations in the Amplitude of a Carrier Phase-shift keying (PSK is a Digital Modulation scheme that conveys data by changing or modulating the phase of a reference signal In Digital modulation, Minimum-shift keying (MSK is a type of continuous phase Frequency-shift keying that was developed in the late 1960s Continuous phase modulation ( CPM) is a method for modulation of data commonly used in Wireless modems In contrast to other coherent digital Phase Pulse-position modulation is a form of signal Modulation in which M message bits are encoded by transmitting asingle pulse in one of 2^M possible time-shifts In Telecommunication, trellis modulation (also known as trellis coded modulation, or simply TCM) is a modulation scheme which allows highly efficient Orthogonal frequency-division multiplexing ( OFDM) — essentially identical to Coded OFDM ( COFDM) and Discrete multi-tone modulation ( Spread-spectrum techniques are methods by which Energy generated in a particular bandwidth is deliberately spread in the Frequency domain, resulting Frequency-hopping spread spectrum ( FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using In Telecommunications direct-sequence spread spectrum ( DSSS) is a Modulation technique Morse code is a Character encoding for transmitting telegraphic information using standardized sequences of short and long elements to represent the letters numerals Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Amplitude is the magnitude of change in the oscillating variable with each Oscillation, within an oscillating system Frequency is a measure of the number of occurrences of a repeating event per unit Time. Continuous wave is also the name given to an early method of radio transmission, in which a carrier wave is switched on and off. Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. In Telecommunications transmission is the process of sending propagating and receiving an analogue or digital information signal over a physical point-to-point or In Telecommunications, a carrier wave, or carrier is a Waveform (usually Sinusoidal) that is modulated (modified with an input signal Information is carried in the varying duration of the on and off periods of the signal. Information as a concept has a diversity of meanings from everyday usage to technical settings On-off keying ( OOK) is a type of Modulation that represents Digital Data as the presence or absence of a Carrier wave. In radio transmission, CW waves are also known as "undamped waves", to distinguish this method from damped wave transmission. A damped wave is an electromagnetic wave whose Amplitude of Oscillation decreases with time eventually going to zero

Radio

Very early radio transmitters used a spark gap to produce radio-frequency oscillations in the transmitting antenna; the signals produced by these spark-gap transmitters had a characteristic rapidly damped amplitude during each pulse of radiated energy. A spark gap consists of an arrangement of two conducting Electrodes separated by a gap usually filled with a Gas such as Air. A spark-gap transmitter is a device for generating Radio frequency electromagnetic waves. When alternators and later electronic oscillators became available, the signal strength remained constant during each code element, leading to the description of this technique as "continuous" waves. alternator is an electromechanical device that converts mechanical energy to Alternating current electrical energy Oscillation is the repetitive variation typically in Time, of some measure about a central value (often a point of Equilibrium) or between two or more different states

An unmodulated carrier has no bandwidth and conveys no information; the act of keying the carrier on and off produces a finite bandwidth relating to the transmission rate. Strictly speaking, a keyed carrier may be referred to as "ICW" for "Interrupted continuous wave" but the necessity of keying is usually understood.

A commercially manufactured paddle for use with electronic keyer to generate Morse code

Early radio transmitters were incapable of handling the complexity of actual audio and therefore CW was the only form of communication available. CW still remained a viable form of radio communication for many years after voice transmission was perfected, because simple transmitters could be used. The low bandwidth of the code signal, due in part to low information transmission rate, allowed very selective filters to be used in the receiver which blocked out much of the atmospheric noise that would otherwise reduce the intelligibility of the signal.

Continuous-wave radio was called radiotelegraphy because like the telegraph, it worked by means of a simple switch to transmit Morse code. Morse code is a Character encoding for transmitting telegraphic information using standardized sequences of short and long elements to represent the letters numerals However, instead of controlling the electricity in a cross-country wire, the switch controlled the power sent to a radio transmitter. For biologic transmitters see Transmitter substance. A transmitter is an electronic device which usually with the aid of an antenna This mode is still in common use by amateur radio operators. Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications

A continuous-wave radar system is one where a continuous wave is transmitted by one aerial while a second aerial receives the reflected radio energy. Continuous-wave radar system is a Radar system where a known stable frequency Continuous wave Radio energy is transmitted and then received from any reflecting An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light.

In amateur radio, the terms "CW" and "Morse code" are often used interchangeably, despite the distinctions between the two. Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications Morse code may be sent using direct current in wires, sound, or light, for example. Direct current ( DC) is the unidirectional flow of Electric charge.

Key clicks

In morse (on off carrier keying), if the carrier wave is turned on or off rapidly, the bandwidth will be large; if the carrier turns on and off more slowly the bandwidth will be smaller. The problem of excessive bandwidth used by a morse transmitter which turns on/off too quickly is known as key clicks. Morse code is a Character encoding for transmitting telegraphic information using standardized sequences of short and long elements to represent the letters numerals For biologic transmitters see Transmitter substance. A transmitter is an electronic device which usually with the aid of an antenna Certain types of power amplifiers used in a transmitter may increase the problematic effects of key clicks.

Laser physics

In laser physics and engineering the term "continuous wave" or "CW" refers to a laser which produces a continuous output beam, sometimes referred to as 'free-running'. Laser science or laser physics is a branch of Optics that describes the theory and practice of Lasers Laser science is principally concerned with A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. This is as opposed to a q-switched, gain-switched or modelocked laser, which produces pulses of light. Q-switching, sometimes known as giant pulse formation, is a technique by which a Laser can be made to produce a pulsed output beam Gain-switching is a technique in Optics by which a Laser can be made to produce pulses of Light of extremely short duration of the order of picoseconds Mode-locking is a technique in Optics by which a Laser can be made to produce pulses of Light of extremely short duration on the order of picoseconds (10-12s

See also

• Damped wave
• On-off keying
• Amplitude modulation
• Types of radio emissions

References

• Larry D. A damped wave is an electromagnetic wave whose Amplitude of Oscillation decreases with time eventually going to zero On-off keying ( OOK) is a type of Modulation that represents Digital Data as the presence or absence of a Carrier wave. Amplitude modulation ( AM) is a technique used in electronic communication most commonly for transmitting information via a Radio Carrier wave The International Telecommunication Union uses an internationally agreed system for classifying Radio frequency signals Wolfgang et. al, (ed), The ARRL Handbook for Radio Amateurs, Sixty-Eighth Edition , (1991), ARRL, Newington CT USA ISBN 0-87259-168-9
• CW Bandwidth Described