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69-468: A major advantage of the TWT over some other microwave tubes is its ability to amplify a wide range of frequencies i.e. a large bandwidth . The bandwidth of the helix TWT can be as high as two octaves , while the cavity versions have bandwidths of 10–20%. Operating frequencies range from 300 MHz to 50 GHz. The power gain of the tube is on the order of 40 to 70 decibels , and output power ranges from

138-584: A a 2 + b 2 cos ⁡ s a 2 + b 2 i + − a a 2 + b 2 sin ⁡ s a 2 + b 2 j + 0 k {\displaystyle {\frac {d\mathbf {T} }{ds}}=\kappa \mathbf {N} ={\frac {-a}{a^{2}+b^{2}}}\cos {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {i} +{\frac {-a}{a^{2}+b^{2}}}\sin {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {j} +0\mathbf {k} } Its curvature

207-976: A 2 + b 2 | a | = ( − a sin ⁡ t ) 2 + ( a cos ⁡ t ) 2 = a s ( t ) = ∫ 0 t a 2 + b 2 d τ = a 2 + b 2 t {\displaystyle {\begin{aligned}\mathbf {r} &=a\cos t\mathbf {i} +a\sin t\mathbf {j} +bt\mathbf {k} \\[6px]\mathbf {v} &=-a\sin t\mathbf {i} +a\cos t\mathbf {j} +b\mathbf {k} \\[6px]\mathbf {a} &=-a\cos t\mathbf {i} -a\sin t\mathbf {j} +0\mathbf {k} \\[6px]|\mathbf {v} |&={\sqrt {(-a\sin t)^{2}+(a\cos t)^{2}+b^{2}}}={\sqrt {a^{2}+b^{2}}}\\[6px]|\mathbf {a} |&={\sqrt {(-a\sin t)^{2}+(a\cos t)^{2}}}=a\\[6px]s(t)&=\int _{0}^{t}{\sqrt {a^{2}+b^{2}}}d\tau ={\sqrt {a^{2}+b^{2}}}t\end{aligned}}} So

276-442: A 2 + b 2 i − b cos ⁡ s a 2 + b 2 j + a k ) d B d s = 1 a 2 + b 2 ( b cos ⁡ s a 2 + b 2 i + b sin ⁡ s

345-430: A 2 + b 2 j + 0 k {\displaystyle \mathbf {N} =-\cos {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {i} -\sin {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {j} +0\mathbf {k} } The binormal vector is B = T × N = 1 a 2 + b 2 ( b sin ⁡ s

414-565: A 2 + b 2 j + 0 k ) {\displaystyle {\begin{aligned}\mathbf {B} =\mathbf {T} \times \mathbf {N} &={\frac {1}{\sqrt {a^{2}+b^{2}}}}\left(b\sin {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {i} -b\cos {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {j} +a\mathbf {k} \right)\\[12px]{\frac {d\mathbf {B} }{ds}}&={\frac {1}{a^{2}+b^{2}}}\left(b\cos {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {i} +b\sin {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {j} +0\mathbf {k} \right)\end{aligned}}} Its torsion

483-455: A 2 + b 2 k {\displaystyle {\frac {d\mathbf {r} }{ds}}=\mathbf {T} ={\frac {-a}{\sqrt {a^{2}+b^{2}}}}\sin {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {i} +{\frac {a}{\sqrt {a^{2}+b^{2}}}}\cos {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {j} +{\frac {b}{\sqrt {a^{2}+b^{2}}}}\mathbf {k} } The normal vector is d T d s = κ N = −

552-459: A sin ⁡ t i + a cos ⁡ t j + b k a = − a cos ⁡ t i − a sin ⁡ t j + 0 k | v | = ( − a sin ⁡ t ) 2 + ( a cos ⁡ t ) 2 + b 2 =

621-510: A / b ⁠ (or pitch 2 πb ) expressed in Cartesian coordinates as the parametric equation has an arc length of a curvature of and a torsion of A helix has constant non-zero curvature and torsion. A helix is the vector-valued function r = a cos ⁡ t i + a sin ⁡ t j + b t k v = −

690-566: A general helix or cylindrical helix if its tangent makes a constant angle with a fixed line in space. A curve is a general helix if and only if the ratio of curvature to torsion is constant. A curve is called a slant helix if its principal normal makes a constant angle with a fixed line in space. It can be constructed by applying a transformation to the moving frame of a general helix. For more general helix-like space curves can be found, see space spiral ; e.g., spherical spiral . Helices can be either right-handed or left-handed. With

759-441: A specific range of frequencies . The audible frequency range for humans is typically given as being between about 20 Hz and 20,000 Hz (20 kHz), though the high frequency limit usually reduces with age. Other species have different hearing ranges. For example, some dog breeds can perceive vibrations up to 60,000 Hz. In many media, such as air, the speed of sound is approximately independent of frequency, so

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828-402: A "drift tube" in which faster electrons overtake the slower ones, creating the bunches, after which the electrons pass through another resonant cavity from which the output power is taken. Since the velocity sorting process takes time, the drift tube must often be several feet long. In comparison, in the TWT the acceleration is caused by the interactions with the helix along the entire length of

897-428: A "spiral" (helical) ramp – is a surface called a helicoid . The pitch of a helix is the height of one complete helix turn , measured parallel to the axis of the helix. A double helix consists of two (typically congruent ) helices with the same axis, differing by a translation along the axis. A circular helix (i.e. one with constant radius) has constant band curvature and constant torsion . The slope of

966-461: A broadband TWTA can be as high as one octave , although tuned (narrowband) versions exist; operating frequencies range from 300 MHz to 50 GHz. A TWTA consists of a traveling-wave tube coupled with its protection circuits (as in klystron ) and regulated power supply electronic power conditioner (EPC), which may be supplied and integrated by a different manufacturer. The main difference between most power supplies and those for vacuum tubes

1035-399: A circular helix is commonly defined as the ratio of the circumference of the circular cylinder that it spirals around, and its pitch (the height of one complete helix turn). A conic helix , also known as a conic spiral , may be defined as a spiral on a conic surface, with the distance to the apex an exponential function of the angle indicating direction from the axis. A curve is called

1104-500: A control grid is typically introduced between the TWT's electron gun and slow-wave structure to allow pulsed operation. The circuit that drives the control grid is usually referred to as a grid modulator . TWTAs have found applications in a number of spacecraft, including all five of the space probes that have achieved the escape velocity to leave the Solar System. For example, dual redundant 12-watt X-band TWTAs are mounted on

1173-405: A few watts to megawatts . TWTs are widely used as the power amplifiers and oscillators in radar systems, communication satellite and spacecraft transmitters , and electronic warfare systems. The TWT is an elongated vacuum tube with an electron gun (a heated cathode that emits electrons ) at one end. A voltage applied across the cathode and anode accelerates the electrons towards

1242-411: A fractional error of Δ f f = 1 2 f T m {\textstyle {\frac {\Delta f}{f}}={\frac {1}{2fT_{\text{m}}}}} where T m {\displaystyle T_{\text{m}}} is the timing interval and f {\displaystyle f} is the measured frequency. This error decreases with frequency, so it

1311-608: A helix can be reparameterized as a function of s , which must be unit-speed: r ( s ) = a cos ⁡ s a 2 + b 2 i + a sin ⁡ s a 2 + b 2 j + b s a 2 + b 2 k {\displaystyle \mathbf {r} (s)=a\cos {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {i} +a\sin {\frac {s}{\sqrt {a^{2}+b^{2}}}}\mathbf {j} +{\frac {bs}{\sqrt {a^{2}+b^{2}}}}\mathbf {k} } The unit tangent vector

1380-490: A helix is a curve in 3- dimensional space. The following parametrisation in Cartesian coordinates defines a particular helix; perhaps the simplest equations for one is As the parameter t increases, the point ( x ( t ) , y ( t ) , z ( t ) ) {\displaystyle (x(t),y(t),z(t))} traces a right-handed helix of pitch 2 π (or slope 1) and radius 1 about

1449-416: A known frequency near the unknown frequency is mixed with the unknown frequency in a nonlinear mixing device such as a diode . This creates a heterodyne or "beat" signal at the difference between the two frequencies. If the two signals are close together in frequency the heterodyne is low enough to be measured by a frequency counter. This process only measures the difference between the unknown frequency and

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1518-402: A repeating event is accomplished by counting the number of times that event occurs within a specific time period, then dividing the count by the period. For example, if 71 events occur within 15 seconds the frequency is: f = 71 15 s ≈ 4.73 Hz . {\displaystyle f={\frac {71}{15\,{\text{s}}}}\approx 4.73\,{\text{Hz}}.} If

1587-483: A second (60 seconds divided by 120). For cyclical phenomena such as oscillations , waves , or for examples of simple harmonic motion , the term frequency is defined as the number of cycles or repetitions per unit of time. The conventional symbol for frequency is f or ν (the Greek letter nu ) is also used. The period T is the time taken to complete one cycle of an oscillation or rotation. The frequency and

1656-451: A series of coupled cavities arranged axially along the beam. This structure provides a helical waveguide , and hence amplification can occur via velocity modulation. Helical waveguides have very nonlinear dispersion and thus are only narrowband (but wider than klystron ). A coupled-cavity TWT can achieve 60 kW output power. Operation is similar to that of a klystron , except that coupled-cavity TWTs are designed with attenuation between

1725-397: Is d r d s = T = − a a 2 + b 2 sin ⁡ s a 2 + b 2 i + a a 2 + b 2 cos ⁡ s a 2 + b 2 j + b

1794-471: Is κ = | d T d s | = | a | a 2 + b 2 {\displaystyle \kappa =\left|{\frac {d\mathbf {T} }{ds}}\right|={\frac {|a|}{a^{2}+b^{2}}}} . The unit normal vector is N = − cos ⁡ s a 2 + b 2 i − sin ⁡ s

1863-735: Is τ = | d B d s | = b a 2 + b 2 . {\displaystyle \tau =\left|{\frac {d\mathbf {B} }{ds}}\right|={\frac {b}{a^{2}+b^{2}}}.} An example of a double helix in molecular biology is the nucleic acid double helix . An example of a conic helix is the Corkscrew roller coaster at Cedar Point amusement park. Some curves found in nature consist of multiple helices of different handedness joined together by transitions known as tendril perversions . Most hardware screw threads are right-handed helices. The alpha helix in biology as well as

1932-559: Is a shape like a cylindrical coil spring or the thread of a machine screw . It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology , as the DNA molecule is formed as two intertwined helices , and many proteins have helical substructures, known as alpha helices . The word helix comes from the Greek word ἕλιξ , "twisted, curved". A "filled-in" helix – for example,

2001-495: Is called a radio wave . Likewise, an electromagnetic wave with a frequency higher than 8 × 10  Hz will also be invisible to the human eye; such waves are called ultraviolet (UV) radiation. Even higher-frequency waves are called X-rays , and higher still are gamma rays . All of these waves, from the lowest-frequency radio waves to the highest-frequency gamma rays, are fundamentally the same, and they are all called electromagnetic radiation . They all travel through vacuum at

2070-602: Is called a linearized TWTA (LTWTA, "EL-tweet-uh"). Broadband TWTAs generally use a helix TWT and achieve less than 2.5 kW output power. TWTAs using a coupled cavity TWT can achieve 15 kW output power, but at the expense of narrower bandwidth. The original design and prototype of the TWT was done by Andrei "Andy" Haeff c. 1931 while he was working as a doctoral student at the Kellogg Radiation Laboratory at Caltech. His original patent, "Device for and Method of Controlling High Frequency Currents",

2139-554: Is dated November 12, 1942, and he built his first TWT in early 1943. The TWT was later refined by Kompfner, John R. Pierce , and Lester M. Winslow at Bell Labs . Note that Kompfner's US patent, granted in 1953, does cite Haeff's previous work. By the 1950s, after further development at the Electron Tube Laboratory at Hughes Aircraft Company in Culver City, California, TWTs went into production there, and by

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2208-405: Is equivalent to one hertz. As a matter of convenience, longer and slower waves, such as ocean surface waves , are more typically described by wave period rather than frequency. Short and fast waves, like audio and radio, are usually described by their frequency. Some commonly used conversions are listed below: For periodic waves in nondispersive media (that is, media in which the wave speed

2277-422: Is expressed with the unit reciprocal second (s ) or, in the case of radioactivity, with the unit becquerel . It is defined as a rate , f = N /Δ t , involving the number of entities counted or the number of events happened ( N ) during a given time duration (Δ t ); it is a physical quantity of type temporal rate . Helix A helix ( / ˈ h iː l ɪ k s / ; pl.   helices )

2346-411: Is generally a problem at low frequencies where the number of counts N is small. An old method of measuring the frequency of rotating or vibrating objects is to use a stroboscope . This is an intense repetitively flashing light ( strobe light ) whose frequency can be adjusted with a calibrated timing circuit. The strobe light is pointed at the rotating object and the frequency adjusted up and down. When

2415-458: Is independent of frequency), frequency has an inverse relationship to the wavelength , λ ( lambda ). Even in dispersive media, the frequency f of a sinusoidal wave is equal to the phase velocity v of the wave divided by the wavelength λ of the wave: f = v λ . {\displaystyle f={\frac {v}{\lambda }}.} In the special case of electromagnetic waves in vacuum , then v = c , where c

2484-402: Is red light, 800 THz ( 8 × 10  Hz ) is violet light, and between these (in the range 400–800 THz) are all the other colors of the visible spectrum . An electromagnetic wave with a frequency less than 4 × 10  Hz will be invisible to the human eye; such waves are called infrared (IR) radiation. At even lower frequency, the wave is called a microwave , and at still lower frequencies it

2553-466: Is that efficient vacuum tubes have depressed collectors to recycle kinetic energy of the electrons, so the secondary winding of the power supply needs up to 6 taps of which the helix voltage needs precise regulation. The subsequent addition of a linearizer (as for inductive output tube ) can, by complementary compensation, improve the gain compression and other characteristics of the TWTA; this combination

2622-400: Is the speed of light in vacuum, and this expression becomes f = c λ . {\displaystyle f={\frac {c}{\lambda }}.} When monochromatic waves travel from one medium to another, their frequency remains the same—only their wavelength and speed change. Measurement of frequency can be done in the following ways: Calculating the frequency of

2691-400: Is the number of occurrences of a repeating event per unit of time . It is also occasionally referred to as temporal frequency for clarity and to distinguish it from spatial frequency . Ordinary frequency is related to angular frequency (symbol ω , with SI unit radian per second) by a factor of 2 π . The period (symbol T ) is the interval of time between events, so the period is

2760-423: The A and B forms of DNA are also right-handed helices. The Z form of DNA is left-handed. In music , pitch space is often modeled with helices or double helices, most often extending out of a circle such as the circle of fifths , so as to represent octave equivalency . In aviation, geometric pitch is the distance an element of an airplane propeller would advance in one revolution if it were moving along

2829-447: The klystron . All of these tubes use the same basic "bunching" of electrons to provide the amplification process, and differ largely in what process causes the velocity modulation to occur. In the klystron, the electron beam passes through a hole in a resonant cavity which is connected to the source RF signal. The signal at the instant the electrons pass through the hole causes them to be accelerated (or decelerated). The electrons enter

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2898-408: The reciprocal of the frequency: T = 1/ f . Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals ( sound ), radio waves , and light . For example, if a heart beats at a frequency of 120 times per minute (2 hertz), the period—the time interval between beats—is half

2967-458: The z -axis, in a right-handed coordinate system. In cylindrical coordinates ( r , θ , h ) , the same helix is parametrised by: A circular helix of radius a and slope ⁠ a / b ⁠ (or pitch 2 πb ) is described by the following parametrisation: Another way of mathematically constructing a helix is to plot the complex-valued function e as a function of the real number x (see Euler's formula ). The value of x and

3036-656: The 1960s TWTs were also produced by such companies as the English Electric Valve Company , followed by Ferranti in the 1970s. On July 10, 1962, the first communications satellite, Telstar 1 , was launched with a 2 W, 4 GHz RCA-designed TWT transponder used for transmitting RF signals to Earth stations. Syncom 2 was successfully launched into geosynchronous orbit on July 26, 1963, with two 2 W, 1850 MHz Hughes-designed TWT transponders — one active and one spare. TWTAs are commonly used as amplifiers in satellite transponders , where

3105-491: The alternating current in household electrical outlets is 60 Hz (between the tones B ♭ and B; that is, a minor third above the European frequency). The frequency of the ' hum ' in an audio recording can show in which of these general regions the recording was made. Aperiodic frequency is the rate of incidence or occurrence of non- cyclic phenomena, including random processes such as radioactive decay . It

3174-678: The body under the dish of the New Horizons spacecraft, which visited Pluto in 2015, then Kuiper belt object 486958 Arrokoth in 2019 to return data at a distance of 43.4 AU from the Sun. Launched in 2021, James Webb Space Telescope makes use of K a -band TWTs. A TWT has sometimes been referred to as a "traveling-wave amplifier tube" (TWAT), although this term was never widely adopted. "TWT" has been pronounced by engineers as "twit", and "TWTA" as "tweeta". Frequency Frequency (symbol f ), most often measured in hertz (symbol: Hz),

3243-400: The cathode. Higher powered helix TWTs usually contain beryllium oxide ceramic as both a helix support rod and in some cases, as an electron collector for the TWT because of its special electrical, mechanical, and thermal properties. There are a number of RF amplifier tubes that operate in a similar fashion to the TWT, known collectively as velocity-modulated tubes. The best known example is

3312-459: The center of the helix, where the electrons are flowing. Depending on the phase of the signal, the electrons will either be sped up or slowed down as they pass the windings. This causes the electron beam to "bunch up", known technically as "velocity modulation". The resulting pattern of electron density in the beam is an analog of the original RF signal. Because the beam is passing the helix as it travels, and that signal varies, it causes induction in

3381-416: The far end of the tube, and an external magnetic field around the tube focuses the electrons into a beam. At the other end of the tube the electrons strike the "collector", which returns them to the circuit. Wrapped around the inside of the tube, just outside the beam path, is a helix of wire, typically oxygen-free copper . The RF signal to be amplified is fed into the helix at a point near the emitter end of

3450-421: The frequency of the strobe equals the frequency of the rotating or vibrating object, the object completes one cycle of oscillation and returns to its original position between the flashes of light, so when illuminated by the strobe the object appears stationary. Then the frequency can be read from the calibrated readout on the stroboscope. A downside of this method is that an object rotating at an integer multiple of

3519-404: The helix wire. As power level increases, the wire can overheat and cause the helix geometry to warp. Wire thickness can be increased to improve matters, but if the wire is too thick it becomes impossible to obtain the required helix pitch for proper operation. Typically helix TWTs achieve less than 2.5 kW output power. The coupled-cavity TWT overcomes this limit by replacing the helix with

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3588-455: The helix, amplifying the original signal. By the time it reaches the other end of the tube, this process has had time to deposit considerable energy back into the helix. A second directional coupler, positioned near the collector, receives an amplified version of the input signal from the far end of the RF circuit. Attenuators placed along the RF circuit prevent the reflected wave from traveling back to

3657-461: The input signal is very weak and the output needs to be high power. TWTAs used in satellite communications are considered as reliable choices and tend to live beyond their expected lifetime of 15-20 years. A TWTA whose output drives an antenna is a type of transmitter . TWTA transmitters are used extensively in radar , particularly in airborne fire-control radar systems, and in electronic warfare and self-protection systems. In such applications,

3726-427: The line of sight along the helix's axis, if a clockwise screwing motion moves the helix away from the observer, then it is called a right-handed helix; if towards the observer, then it is a left-handed helix. Handedness (or chirality ) is a property of the helix, not of the perspective: a right-handed helix cannot be turned to look like a left-handed one unless it is viewed in a mirror, and vice versa. In mathematics ,

3795-545: The number of counts is not very large, it is more accurate to measure the time interval for a predetermined number of occurrences, rather than the number of occurrences within a specified time. The latter method introduces a random error into the count of between zero and one count, so on average half a count. This is called gating error and causes an average error in the calculated frequency of Δ f = 1 2 T m {\textstyle \Delta f={\frac {1}{2T_{\text{m}}}}} , or

3864-601: The period are related by the equation f = 1 T . {\displaystyle f={\frac {1}{T}}.} The term temporal frequency is used to emphasise that the frequency is characterised by the number of occurrences of a repeating event per unit time. The SI unit of frequency is the hertz (Hz), named after the German physicist Heinrich Hertz by the International Electrotechnical Commission in 1930. It

3933-419: The real and imaginary parts of the function value give this plot three real dimensions. Except for rotations , translations , and changes of scale, all right-handed helices are equivalent to the helix defined above. The equivalent left-handed helix can be constructed in a number of ways, the simplest being to negate any one of the x , y or z components. A circular helix of radius a and slope ⁠

4002-410: The reference frequency. To convert higher frequencies, several stages of heterodyning can be used. Current research is extending this method to infrared and light frequencies ( optical heterodyne detection ). Visible light is an electromagnetic wave , consisting of oscillating electric and magnetic fields traveling through space. The frequency of the wave determines its color: 400 THz ( 4 × 10 Hz)

4071-560: The rotation rate of a shaft, mechanical vibrations, or sound waves , can be converted to a repetitive electronic signal by transducers and the signal applied to a frequency counter. As of 2018, frequency counters can cover the range up to about 100 GHz. This represents the limit of direct counting methods; frequencies above this must be measured by indirect methods. Above the range of frequency counters, frequencies of electromagnetic signals are often measured indirectly utilizing heterodyning ( frequency conversion ). A reference signal of

4140-414: The same speed (the speed of light), giving them wavelengths inversely proportional to their frequencies. c = f λ , {\displaystyle \displaystyle c=f\lambda ,} where c is the speed of light ( c in vacuum or less in other media), f is the frequency and λ is the wavelength. In dispersive media , such as glass, the speed depends somewhat on frequency, so

4209-413: The slow-wave structure instead of a drift tube. The slow-wave structure gives the TWT its wide bandwidth. A free electron laser allows higher frequencies. A TWT integrated with a regulated power supply and protection circuits is referred to as a traveling-wave-tube amplifier (abbreviated TWTA and often pronounced "TWEET-uh"). It is used to produce high-power radio frequency signals. The bandwidth of

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4278-419: The source of the electron beam and they both directed the beam down the center of the helix instead of outside of it. These configuration changes resulted in much greater wave amplification than Haeff's design as they relied on the physical principles of velocity modulation and electron bunching. Kompfner developed his TWT in a British Admiralty radar laboratory during World War II . His first sketch of his TWT

4347-461: The strobing frequency will also appear stationary. Higher frequencies are usually measured with a frequency counter . This is an electronic instrument which measures the frequency of an applied repetitive electronic signal and displays the result in hertz on a digital display . It uses digital logic to count the number of cycles during a time interval established by a precision quartz time base. Cyclic processes that are not electrical, such as

4416-399: The tube. The signal is normally fed into the helix via a waveguide or electromagnetic coil placed at one end, forming a one-way signal path, a directional coupler . By controlling the accelerating voltage, the speed of the electrons flowing down the tube is set to be similar to the speed of the RF signal running down the helix. The signal in the wire causes a magnetic field to be induced in

4485-440: The tube. This allows the TWT to have a very low noise output, a major advantage of the design. More usefully, this process is much less sensitive to the physical arrangement of the tube, which allows the TWT to operate over a wider variety of frequencies. TWT's are generally at an advantage when low noise and frequency variability are useful. Helix TWTs are limited in peak RF power by the current handling (and therefore thickness) of

4554-419: The wavelength is not quite inversely proportional to frequency. Sound propagates as mechanical vibration waves of pressure and displacement, in air or other substances. In general, frequency components of a sound determine its "color", its timbre . When speaking about the frequency (in singular) of a sound, it means the property that most determines its pitch . The frequencies an ear can hear are limited to

4623-462: The wavelength of the sound waves (distance between repetitions) is approximately inversely proportional to frequency. In Europe , Africa , Australia , southern South America , most of Asia , and Russia , the frequency of the alternating current in household electrical outlets is 50 Hz (close to the tone G), whereas in North America and northern South America, the frequency of

4692-457: Was adopted by the CGPM (Conférence générale des poids et mesures) in 1960, officially replacing the previous name, cycle per second (cps). The SI unit for the period, as for all measurements of time, is the second . A traditional unit of frequency used with rotating mechanical devices, where it is termed rotational frequency , is revolution per minute , abbreviated r/min or rpm. 60 rpm

4761-537: Was filed in 1933 and granted in 1936. The invention of the TWT is often attributed to Rudolf Kompfner in 1942–1943. In addition, Nils Lindenblad, working at RCA (Radio Corporation of America) in the USA also filed a patent for a device in May 1940 that was remarkably similar to Kompfner's TWT. Both of these devices were improvements over Haeff's original design as they both used the then newly invented precision electron gun as

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