122 Sentences With "dipole antenna" | Random Sentence Generator

A use for this is the combination of a symmetric dipole antenna with a coaxial line.

An electric dipole antenna was used to study the electric fields of plasmas, while two search coil magnetic antennas studied the magnetic fields. The electric dipole antenna was mounted at the tip of the magnetometer boom. The search coil magnetic antennas were mounted on the high-gain antenna feed. Nearly simultaneous measurements of the electric and magnetic field spectrum allowed electrostatic waves to be distinguished from electromagnetic waves.

Isotron is the trade name for a shortwave antenna marketed by Bilal Co. for use as an amateur radio transmitting antenna for restricted spaces.Ralph Bilal, Bilal Company website, 2011, Florissant, Colorado It is physically short as compared to a dipole antenna for a given frequency. It consists of a coil placed between two angled sheet metal plates. The bandwidth of the Isotron is quite narrow as compared with a dipole antenna.

A coaxial antenna (often known as a coaxial dipole) is a particular form of a half-wave dipole antenna, most often employed as a vertically polarized omnidirectional antenna.

For typical conditions in the solar wind λDe ~ 7–20 m, much shorter than the wire dipole antenna on Wind. The majority of this section was taken from.

A typical monopole antenna has an omnidirectional radiation pattern; it radiates equal radio power in all azimuthal directions perpendicular to the antenna axis, with the signal power decreasing with elevation angle to a null (point of zero radiated power) at the zenith. A monopole antenna can be thought of as a dipole antenna where one end of the dipole antenna now becomes the ground plane for said monopole antenna. By this line of conceptual thinking, one can easily reach the conclusion that the radiation emanating from a monopole antenna exists in half the space of similar dipole antenna. Therefore, the maximum gain is twice that, or an addition 3 dB, of the maximum gain of typical dipole.

It has two main sensors a dipole antenna and a magnetic search coil. The dipole antenna has two whip antenna's that extend 2.8 meters (110 inches/ 9.1 feet) and they are attached to the main body of the spacecraft. This sensor has been compared to a rabbit ears set-top TV antenna. The search coil is overall a mu metal rod 15 cm (6 in) length with a fine copper wire wound 10,000 times around it.

UHF half-wave dipole Dipole antenna used by the radar altimeter in an airplane Animated diagram of a half-wave dipole antenna receiving a radio wave. The antenna consists of two metal rods connected to a receiver R. The electric field (E, green arrows) of the incoming wave pushes the electrons in the rods back and forth, charging the ends alternately positive (+) and negative (−). Since the length of the antenna is one half the wavelength of the wave, the oscillating field induces standing waves of voltage (V, represented by red band) and current in the rods. The oscillating currents (black arrows) flow down the transmission line and through the receiver (represented by the resistance R). In radio and telecommunications a dipole antenna or doublet is the simplest and most widely used class of antenna.

The physical communication mean used is the inductive coupling signaling working in the near field of a 131 kHz magnetic dipole antenna. Inductive coupling power falls cubically with the distance between the Controller and Responder.

In 1924 Lévy invented the horizontal dipole antenna with feeder, and in 1925 the V antenna, polyphase antennas and folded dipole antenna. In 1924 the horizontal polarized antenna let Levy obtain experiment results that confirmed the existence of the ionizing Heaviside Layer. In 1925 Lévy was president of SPIR (Syndicat Professionnel des Industries Radioélectriques). In an attempt to stimulate sales of radio receivers, in March 1926 his company launched Radio LL using a 1 kW transmitted from the rue de Javel facility in Paris.

EPFCGs), electromagnetic pulse generators, electromagnetic weapons, vector inversion generators, etc. A 2.4 megawatt HERF generator (an EDFEG with a pulse forming network directly driving a dipole antenna) with peak output frequency at 21.4 MHz was demonstrated.

"Rabbit-ears" VHF television antenna (the small loop is a separate UHF antenna). One of the most common applications of the dipole antenna is the rabbit ears or bunny ears television antenna, found atop broadcast television receivers. It is used to receive the VHF terrestrial television bands, consisting in the US of 54 to 88 MHz (band I) and 174 to 216 MHz (band III), with wavelengths of 5.5 to 1.4 m. Since this frequency range is much wider than a single fixed dipole antenna can cover, it is made with several degrees of adjustment.

In a monopole antenna, the radiation pattern of the monopole plus the virtual "image antenna" make it appear as a two element center-fed dipole antenna. So a monopole mounted over an ideal ground plane has a radiation pattern identical to a dipole antenna. The feedline from the transmitter or receiver is connected between the bottom end of the monopole element and the ground plane. The ground plane must have good conductivity; any resistance in the ground plane is in series with the antenna, and serves to dissipate power from the transmitter.

Radio stations usually report the power of their transmitters in units of watts, referring to the effective radiated power. This refers to the power that a half-wave dipole antenna would need to radiate to match the intensity of the transmitter's main lobe.

They employ a grid of dipole antennas that are tuned to different frequencies. The interrogator generates a frequency sweep signal and scans for signal dips. Each dipole antenna can encode one bit. The frequency swept will be determined by the antenna length.

The transmitter is a dipole antenna located on top of the station's building in central Hartlepool. The transmitter is low powered broadcasting at 0.025 KW which is just enough to cover all of Hartlepool and the surrounding villages including Hart and Dalton Piercy.

Because ERP is calculated as antenna gain (in a given direction) as compared with the maximum directivity of a half-wave dipole antenna, it creates a mathematically virtual effective dipole antenna oriented in the direction of the receiver. In other words, a notional receiver in a given direction from the transmitter would receive the same power if the source were replaced with an ideal dipole oriented with maximum directivity and matched polarization towards the receiver and with an antenna input power equal to the ERP. The receiver would not be able to determine a difference. Maximum directivity of an ideal half-wave dipole is a constant, i.e.

Like a dipole antenna, a monopole has an omnidirectional radiation pattern: it radiates with equal power in all azimuthal directions perpendicular to the antenna. However, the radiated power varies with elevation angle, with the radiation dropping off to zero at the zenith of the antenna axis. It radiates vertically polarized radio waves. Showing the monopole antenna has the same radiation pattern over perfect ground as a dipole in free space with twice the voltage A monopole can be visualized (right) as being formed by replacing the bottom half of a vertical dipole antenna (c) with a conducting plane (ground plane) at right-angles to the remaining half.

Other reference antennas are also used, especially: •gain relative to a half-wave dipole (Gd), when the reference antenna is a half-wave dipole antenna; •gain relative to a short vertical antenna (Gv), when the reference antenna is a linear conductor, much shorter than one quarter of the wavelength.

This problem is more serious than with a vertical or dipole antenna that is short compared to a wavelength. There matching using a loading coil also generates a high voltage at the antenna end(s). However, unlike with capacitors, the voltage across a physically large inductor is generally not an issue.

As the satellite's experiment is contained entirely within the spacecraft and does not require any external influence (other than the existence of the low-Earth orbit environment), DAVE contains no attitude control system. A deployable UHF dipole antenna was used to provide fairly omnidirectional coverage, negating the need for spacecraft pointing.

The robot dimension is 192x197x79.5 (LxWxH). CRX10 comes packaged with 7 IR floor sensors, 3 obstacle detection PSD sensors and 4 audio sensors. Robot communication is possible via cable (UART), Wi-Fi (Bluetooth) with GAP and SPP profile or dipole antenna with communication distance is more than 100 m. CRX10 supports TTL serial interface.

Antennas for Portable Devices. Chichester: John Wiley, 2007. Print. Therefore, the radio itself, and possibly the user's hand, serves as a rudimentary ground plane. Since these are no larger than the size of the antenna itself, the combination of whip and radio often functions more as an asymmetrical dipole antenna than as a monopole antenna.

The experiment has two low-band instruments, each of which has a dipole antenna pointed to the zenith and observing a single polarisation. The antenna is around in size, sat on a ground shield. It is coupled with a radio receiver, with a 100m cable run to a digital spectrometer. The instruments operate at , and are separated by 150m.

Diagram of electromagnetic wave from a dipole antenna. The orientation of electric vector and the orientation of magnetic vector, is specific as well as chiral. The diagram is non- superposible with its mirror-image. vectors represent how the magnitude and direction of the electric field is constant for an entire plane, which is perpendicular to the direction of travel.

Batwing antennas are a specialized type of crossed dipole antenna, a variant of the turnstile antenna. Two pairs of identical vertical batwing-shaped elements are mounted at right angles around a common mast. Element “wings” on opposite sides are fed as a dipole. To generate an omnidirectional pattern, the two dipoles are fed 90° out of phase.

AO-6 had a 1.3-watt transmitter into a half-wave dipole antenna. AO-6's receiver input sensitivity was approximately -100dBm (2 μV per meter) and had an AGC that provided up to 26 dB of gain reduction optimized for single-sideband modulation. The transceiver team consisted of Karl Meinzer DJ4ZC, Wallace Mercer W4RUD, Dick Daniels WA4DGU and Jan King W3GEY.

The Mk. II was soon upgraded to the Mk. IIA versions, which differed from the Mk. II only in the detail of the scanner antenna; IIA replaced the original dipole antenna at the scanner's focal point with a feed horn that sent the signal back to the receiver in a waveguide, eliminating the lossy coaxial cable of the earlier model.

The wellhead and the ground rod form the two electrodes of a dipole antenna. The voltage difference between the two electrodes is the receive signal that is decoded by a computer. The EM tool generates voltage differences between the drillstring sections in the pattern of very low frequency (2–12 Hz) waves. The data is imposed on the waves through digital modulation.

Dipole antenna polar pattern A common, and basic, radio antenna is the dipole. This has a figure-of-eight polar pattern with two nulls on opposite sides. Highly directional antennae, such as the Yagi have polar patterns very similar to highly directional microphones and for similar reasons. That is, they have multiple small lobes off the main direction with nulls between them.

The TNR measures ~4–256 kHz electric fields in up to 5 logarithmically spaced frequency bands, though typically only set at 3 bands, from 32 or 16 channels per band, with a 7 nV/(Hz)1/2 sensitivity, 400 Hz to 6.4 kHz bandwidth, and total dynamic range in excess of 100 dB. The data are taken by two multi- channel receivers which nominally sample for 20 ms at a 1 MHz sampling rate (see Bougeret 1995 for more information). The TNR is often used to determine the local plasma density by observing the plasma line, an emission at the local upper hybrid frequency due to a thermal noise response of the wire dipole antenna. One should note that observation of the plasma line requires the dipole antenna to be longer than the local Debye length, λDe.

German physicist Heinrich Hertz first demonstrated the existence of radio waves in 1887 using what we now know as a dipole antenna (with capacitative end- loading). On the other hand, Guglielmo Marconi empirically found that he could just ground the transmitter (or one side of a transmission line, if used) dispensing with one half of the antenna, thus realizing the vertical or monopole antenna. For the low frequencies Marconi employed to achieve long- distance communications, this form was more practical; when radio moved to higher frequencies (especially VHF transmissions for FM radio and TV) it was advantageous for these much smaller antennas to be entirely atop a tower thus requiring a dipole antenna or one of its variations. In the early days of radio, the thus-named Marconi antenna (monopole) and the doublet (dipole) were seen as distinct inventions.

The dipole antenna cannot distinguish electrokinetic signal from coseismic signal so it records them both, and coseismic waves must be removed while processing field data to be able to actually interpret electrokinetic effect Zyserman, F., Jouniaux, L., Warden, S., and Garambois, S. (2015). "Borehole seismoelectric logging using a shear- wave source: Possible application to CO2 disposal?." International Journal of Greenhouse Gas Control, 10.1016/j.ijggc.2014.12.

It is the case that a stereo system with external speaker attached by long leads to the main unit (holding the audio electronics) can be troubled by EMC problems which are caused by the speaker leads acting as a dipole antenna. One method of curing this is to add a ferrite choke to the speaker leads close to where they enter the main unit.

A notable decrease in the reactance of the dipole antenna corresponds to the increase in radiated power. The reactive power indicates that the DNG shell acts as a natural matching network for the dipole. The DNG material matches the intrinsic reactance of this antenna system to free space, hence the impedance of DNG material matches free space. It provides a natural matching circuit to the antenna.

The earliest research in metamaterial antennas was an analytical study of a miniature dipole antenna surrounded with a metamaterial. This material is known variously as a negative index metamaterial (NIM) or double negative metamaterial (DNG) among other names. This configuration analytically and numerically appears to produce an order of magnitude increase in power. At the same time, the reactance appears to offer a corresponding decrease.

4, such as ZigBee and 6LoWPAN. Other concurrent standards also exist: ISO/IEC 18000-7 DASH7, infrared networking and ultra-wide band networking. IEEE 1902.1 is unique as it uses a very low frequency and magnetic field modulation (created by a magnetic dipole antenna in the near-field) as the physical mean. The IEEE Working Group on 1902.1 named itself RuBee, after the gem and insect.

Radio operator, Corporal Arthur George Biddle RCS, of 'R1' Patrol using the No 11 Wireless set mounted on a 30 cwt Chevrolet 1533 X2. The rod aerial is just above his head. The four wooden support poles for the Windom dipole antenna are carried on brackets on the wooden 'greedy boards'. The canvas sand mat can be seen rolled up on the right hand vehicle.

Clam Lake ground dipole antenna, showing how it works. The alternating current I in the line is shown flowing in only one direction for clarity. The transmitters operated at a frequency of 76 Hz in the extremely low frequency band, with an alternate capability at 45 Hz and used a combined power of 2.6 megawatts. They were able to communicate with submarines over about half the world's surface.

The monopole antenna was invented in 1895 by radio pioneer Guglielmo Marconi; for this reason it is sometimes called the Marconi antenna. Common types of monopole antenna are the whip, rubber ducky, helical, random wire, umbrella, inverted-L and T-antenna, inverted-F, mast radiator, and ground plane antennas. The load impedance of the quarter-wave monopole is half that of the dipole antenna or 37.5+j21.25 ohms.

Animation of a half-wave dipole antenna radiating radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods connected to a radio transmitter (not shown). The transmitter applies an alternating electric current to the rods, which charges them alternately positive (+) and negative (−). Loops of electric field leave the antenna and travel away at the speed of light; these are the radio waves.

DRAGONSat is a pair of two 5 inches x 5 inches x 5 inches satellites which are launched from the Shuttle orbiter payload bay. Both satellites are built of aluminum with a mass of approximately 7.5 kg. Each picosatellite is covered with photo-voltaic cells and will enable a longer active life in orbit. Each satellite also has a dipole antenna and two antennas for the GPS receiver.

Animation of a half-wave dipole antenna transmitting radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods, with an alternating current applied at its center from a radio transmitter (not shown). The voltage charges the two sides of the antenna alternately positive (+) and negative (−). Loops of electric field (black lines) leave the antenna and travel away at the speed of light; these are the radio waves.

In October 1939 BBC Research engineers experimented with horizontally-polarised transmissions at Start Point. The idea was to see if broadcasts could be made without providing enemy aircraft with a navigational radio beacon. A horizontal dipole antenna was suspended between the two masts. The test was reasonably successful and between 18 February and 15 September 1940 regular transmission were carried in the evenings, on 877 kHz, of what became the "Forces' Programme".

Marvin P. Middlemark (September 16, 1919 – September 14, 1989) invented the Rabbit Ears television antenna (dipole antenna) in 1953 in Rego Park, Queens, New York. Marvin P. Middlemark revolutionized how television was watched in the United States, as his Rabbit Ears increased the television signal reception made available to the mass market; this move is considered by many as the single most important reason for the television boom of the late 1950s – 1960s.

2D simulation: reflection of a quantum particle. White blur represents the probability distribution of finding a particle in a given place if measured. In classical electrodynamics, light is considered as an electromagnetic wave, which is described by Maxwell's equations. Light waves incident on a material induce small oscillations of polarisation in the individual atoms (or oscillation of electrons, in metals), causing each particle to radiate a small secondary wave in all directions, like a dipole antenna.

Five years later, the network changed hands again, this time to the Chenango & Unadilla (C&U;) Telephone Company, which added a second 1 kW transmitter and a Collins/ERI model 300-5 dipole antenna to provide 4.9 kW in the vertical polarization. A 1968 merger with Continental Telephone forced divestiture of C&U;'s broadcast properties, and the entire group of five FM stations, then valued at $600,000, was donated to the Christian Broadcasting Network, headed by Pat Robertson.

With a total height of it is currently the sixth tallest structure in Switzerland. It has a cabin at a height of , containing a coil for feeding the pinnacle, which is insulated against the rest of the tower, separately with high frequency power. Originally the tower was used as a dipole antenna, fed from the cabin. There was another, tall, freestanding lattice tower nearby, dismantled in 2011, which, like the Blosenbergturm, was a tower radiator insulated against ground.

The PRC320 can be used with a number of different Clansman antennas that are supplied with the set; a 2.4m whip antenna is supplied for portable manpack operation using HF groundwave communication. Alternatively a dipole antenna can be used for HF skywave operation. See VRC 321 below for typical ranges achievable using these modes of propagation. The set includes a built-in Antenna Tuning Unit (ATU) which electrically matches the whip antenna length to the radio frequency in use.

Deployable high-gain mesh reflector antenna operating at Ka-band for the Radar in a Cubesat (Raincube). The low cost of CubeSats has enabled unprecedented access to space for smaller institutions and organizations but, for most CubeSat forms, the range and available power is limited to about 2W for its communications antennae. Because of tumbling and low power range, radio-communications are a challenge. Many CubeSats use an omnidirectional monopole or dipole antenna built with commercial measuring tape.

Typically, the inverted vee antenna requires only a single, tall support at the center, and the ends can be insulated and secured to anchors near ground level or near the roof if mounted on a house. This simplified arrangement has several advantages, including a shorter ground distance between the ends. For example, a dipole antenna for the 80 meter band requires a ground length of about from end to end. An inverted vee with a apex elevation requires only .

A regenerative receiver, located some distance from the transmitter, had a dipole antenna mounted on a hand-driven reciprocating mechanism. An aircraft passing into the screened zone would reflect the radiation, and the receiver would detect the Doppler-interference beat between the transmitted and reflected signals. Bistro was first tested during the summer of 1934. With the receiver up to 11 km away from the transmitter, the set could only detect an aircraft entering a screen at about range and under 1,000 m.

The onboard experiments consisted of four step- frequency Ryle-Vonberg radiometers operating from 0.45 MHz to 9.18 MHz, two multichannel total power radiometers operating from 0.2 MHz to 5.4 MHz, one step frequency V-antenna impedance probe operating from 0.24 MHz to 7.86 MHz, and one dipole antenna capacitance probe operating from 0.25 MHz to 2.2 MHz. Explorer 38 was designed for a 1-year minimum operating lifetime. The spacecraft tape recorder performance began to deteriorate after 2 months in orbit.

A rectenna is a rectifying antenna — a special type of receiving antenna that is used for converting electromagnetic energy into direct current (DC) electricity. They are used in wireless power transmission systems that transmit power by radio waves. A simple rectenna element consists of a dipole antenna with an RF diode connected across the dipole elements. The diode rectifies the AC induced in the antenna by the microwaves, to produce DC power, which powers a load connected across the diode.

A halo antenna, or halo, is a horizontally polarized, omnidirectional wavelength dipole antenna, which has been bent into a loop with a small break in the loop on the side directly opposite the feed point. The dipole ends are close but do not meet, and may have an air capacitor between them as needed to establish resonance. A "folded dipole" type of halo. Gain along Y axis 1.2 dBi, Gain along Z axis −1 dBi, Gain along X axis −1.7 dBi.

It was spin stabilised with a dipole antenna producing a pancake shaped waveform. In August 1961, they were contracted to begin building the real satellite. They lost Syncom 1 to electronics failure, but Syncom 2 was successfully placed into a geosynchronous orbit in 1963. Although its inclined orbit still required moving antennas, it was able to relay TV transmissions, and allowed for US President John F. Kennedy to phone Nigerian prime minister Abubakar Tafawa Balewa from a ship on August 23, 1963.

Explorer 38 measured the intensity of celestial radio sources, particularly the Sun, as a function of time, direction and frequency (0.2 MHz to 20 MHz). The spacecraft was gravity gradient oriented. The spacecraft weight was , and average power consumption was 25 W. It carried 2 long V-antennas, one facing toward the Earth and one facing away from the earth. A long dipole antenna was oriented tangentially with respect to the earth's surface. The spacecraft was also equipped with one 136 MHz telemetry turnstile.

73 Electronics on board the I-400s included a Mark 3 Model 1 air search radar equipped with two separate antennas. This unit was capable of detecting aircraft out to a range of . The boats were also equipped with Mark 2 Model 2 air/surface radar sets with distinctive horn-shaped antennas. Each boat carried an E27 radar warning receiver, connected to both a trainable dipole antenna and a fixed non-directional antenna made up of a wire mesh basket and two metal rods.

When accounting for spacecraft potential, these antenna lengths are adjusted to ~41.1 m, ~3.79 m, and ~2.17 m [Note: these are subject to change and only estimates and not necessarily accurate to two decimal places]. The Wind WAVES instrument also detects magnetic fields using three orthogonal search coil magnetometers (designed and built by the University of Iowa). The XY search coils are oriented to be parallel to the XY dipole antenna. The search coils allow for high-frequency magnetic field measurements (defined as Bx, By, and Bz).

The improved scanner introduced on the Mark IIC removed the metal filet from the reflector and replaced the dipole antenna with a waveguide. These were easier to produce because the angular focusing was in the waveguide, allowing the reflector to be linear. It was noted on even the earliest flights of V9977 that a number of basic features of the H2S made it difficult to use. Attempts to fix these began even before H2S entered service, but a number of problems greatly delayed their entry.

The antenna can take different shapes: a spiral, a single dipole antenna, two dipoles with one dipole perpendicular to another, or a folded dipole. The antenna length and geometry depends on the frequency at which the tag operates. Chip and antenna are embedded onto a thin plastic substrate of 100 to 200 nm, for example polymer, PVC, Polyethylenetherephtalate (PET), phenolics, polyesters, styrene, or paper via copper etching or hot stamping. Fastest and cheapest process is via screen printing using conductive ink containing copper, nickel, or carbon.

If the ground plane is large enough, the radio waves from the remaining upper half of the dipole (a) reflected from the ground plane will seem to come from an image antenna (b) forming the missing half of the dipole, which adds to the direct radiation to form a dipole radiation pattern. So the pattern of a monopole with a perfectly conducting, infinite ground plane is identical to the top half of a dipole pattern, with its maximum radiation in the horizontal direction, perpendicular to the antenna. Because it radiates only into the space above the ground plane, or half the space of a dipole antenna, a monopole antenna will have a gain of twice (3 dB greater than) the gain of a similar dipole antenna, and a radiation resistance half that of a dipole. Since a half-wave dipole has a gain of 2.19 dBi and a radiation resistance of 73 ohms, a quarter-wave monopole, the most common type, will have a gain of 2.19 + 3 = 5.19 dBi and a radiation resistance of about 36.8 ohms if it is mounted above a good ground plane.

In 1904, Christian Hülsmeyer gave public demonstrations in Germany and the Netherlands of the use of radio echoes to detect ships so that collisions could be avoided. His device consisted of a simple spark gap used to generate a signal that was aimed using a dipole antenna with a cylindrical parabolic reflector. When a signal reflected from a ship was picked up by a similar antenna attached to the separate coherer receiver, a bell sounded. During bad weather or fog, the device would be periodically spun to check for nearby ships.

A turnstile antenna, or crossed-dipole antenna, is a radio antenna consisting of a set of two identical dipole antennas mounted at right angles to each other and fed in phase quadrature; the two currents applied to the dipoles are 90° out of phase. filed: September 20, 1935; granted: July 13, 1937 The name reflects the notion the antenna looks like a turnstile when mounted horizontally. The antenna can be used in two possible modes. In normal mode the antenna radiates horizontally polarized radio waves perpendicular to its axis.

A slot antenna consists of a metal surface, usually a flat plate, with one or more holes or slots cut out. When the plate is driven as an antenna by an applied radio frequency current, the slot radiates electromagnetic waves in a way similar to a dipole antenna. The shape and size of the slot, as well as the driving frequency, determine the radiation pattern. Slot antennas are usually used at UHF and microwave frequencies at which wavelengths are small enough that the plate and slot are conveniently small.

Shipping also appeared but the team was unable to test this very well as their Handley Page Heyford was forbidden to fly over water. To address this problem, further testing was carried out on two Avro Ansons patrol aircraft. The system was crude, with a simple dipole antenna being held out the window and swung by hand to find returns. For several reasons, the 1.5 m wavelength of the radar system worked better over water than land; notably the large area and flat vertical sides of the ships made excellent radar targets.

To improve the match the antenna is not fed from the end, rather some intermediate point, and the end is grounded instead. In these portable devices the antenna does not have an effective ground plane, the ground side of the transmitter is just connected to the ground connection on its circuit board. Since the circuit board ground is often smaller than the antenna, the antenna/ground combination may function more as an asymmetrical dipole antenna than a monopole. The hand and body of the person holding them may function as a rudimentary ground plane.

At some locations, the radar signal was "blanked" as it passed over television broadcast antenna sites such as Mt. Loma Prieta in the Santa Cruz Mountains, California. However, at DEFCON 3 or higher, the signal was ordered "unblanked" in all directions. The 7.5 megawatt (maximum power) transmitter ran in normal operation at 5 MW output pulse (nearly 20 microseconds in duration) and was conveyed from the transmitter to the antenna feed horn via a diameter rigid coaxial connector. The feed horn consisted of a cross dipole antenna design for both A and B channels.

Local residents were therefore opposed to continued use of the transmitter. In 1998 it was decided that the site could be used for mediumwave transmission and modernization of the facility started. First the old transmitter was replaced by a new, fully transistorized transmitter, which would be also able to operate in DRM mode. In order to allow a good night-time transmission without causing too many problems with electromagnetic influence, a cross-dipole antenna with a radiation maximum pointing vertically into the sky was built in early 2006.

Radiation pattern of a 3λ/2 monopole antenna. Although the radiation of an omnidirectional antenna is symmetrical in azimuthal directions, it may vary in a complicated way with elevation angle, having lobes and nulls at different angles. Common types of low-gain omnidirectional antennas are the whip antenna, "Rubber Ducky" antenna, ground plane antenna, vertically oriented dipole antenna, discone antenna, mast radiator, horizontal loop antenna (sometimes known colloquially as a 'circular aerial' because of the shape) and the halo antenna. Higher-gain omnidirectional antennas can also be built.

Four bay crossed-dipole antenna of an FM broadcasting station. For example, an FM radio station which advertises that it has 100,000 watts of power actually has 100,000 watts ERP, and not an actual 100,000-watt transmitter. The transmitter power output (TPO) of such a station typically may be 10,000 to 20,000 watts, with a gain factor of 5 to 10 (5× to 10×, or 7 to 10 dB). In most antenna designs, gain is realized primarily by concentrating power toward the horizontal plane and suppressing it at upward and downward angles, through the use of phased arrays of antenna elements.

ALLISS antenna as viewed underneath If there is an "S" in the antenna's designation, it is a steerable design. Following the ITU-recommendation, it might be called 'slewable design'. This might be achieved electronically by adjustment of the electrical wave phases of the signals fed to the columns of dipole antenna elements, or physically by mounting the antenna array on a large rotating mechanism. An example of this can be seen at NRK Kvitsøy, where a circular railway carries a pair of wheeled platforms, each of which supports a tower at opposite ends of a diameter-arm.

Illustration of Mars Express with MARSIS antenna deployed On May 4, 2005, Mars Express deployed the first of its two 20-metre- long radar booms for its MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) experiment. At first the boom did not lock fully into place; however, exposing it to sunlight for a few minutes on May 10 fixed the glitch. The second 20 m boom was successfully deployed on June 14. Both 20 m booms were needed to create a 40 m dipole antenna for MARSIS to work; a less crucial 7-meter-long monopole antenna was deployed on June 17.

A dipole antenna exhibits similar properties, and is the basis for the Yagi antenna, which is familiar as the common VHF or UHF television aerial. For much higher frequencies still, parabolic antennas can be used, which are highly directional, focusing received signals from a very narrow angle to a receiving element at the centre. More sophisticated techniques such as phased arrays are generally used for highly accurate direction finding systems called goniometers such as are used in signals intelligence (SIGINT). A helicopter based DF system was designed by ESL Incorporated for the U.S. Government as early as 1972.

The ionosphere's D-layer also affects 80 meters significantly by absorbing signals. During the daylight hours, a station in middle or high latitudes using 100 watts and a simple dipole antenna can expect a maximum communication range of 200 miles (300 km), extending to a few thousand miles or more at night. Global coverage can be routinely achieved during the late fall and winter by a station using modest power and common antennas. The higher background noise on 80 meters, especially when combined with higher ionospheric absorption, causes stations with higher effective radiated power to have a decided advantage in long distance communications.

The antennas have been optimized to have low loss and high reflectivity across the 400–800 MHz observing band of the telescope. Each dish is coupled to a single dual-polarization clover-leaf dipole antenna. The signal is amplified by a pair of low noise amplifiers (LNAs), and transmitted to a centralized computation structure (the "back end") by means of fibre-optic links. At the back end the signal is amplified further by analog amplifier chains, then digitized and correlated with the signals from all other dishes to produce a single coherent image from the whole array.

The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole with a radiating structure supporting a line current so energized that the current has only one node at each end. A dipole antenna commonly consists of two identical conductive elements such as metal wires or rods. The driving current from the transmitter is applied, or for receiving antennas the output signal to the receiver is taken, between the two halves of the antenna. Each side of the feedline to the transmitter or receiver is connected to one of the conductors.

The station's broadcast tower is high that has a seven-foot face on each of its three sides. The tower was built by Stainless Steel Tower of Pennsylvania. The top section has a aerial mast with a side mount dipole antenna for the transmission of analog television programs. The digital antenna is a side mount made by Dielectric and is mounted at . It was completed in 1985 and is the property of LIN TV. On January 11, 2012, it was reported that LIN Media would sell WUPW to Charlotte-based American Spirit Media (owned by Thomas B. Henson) for $22 million.

1982 aerial view of the U.S. Navy Clam Lake, Wisconsin, ELF transmitter facility, used to communicate with deeply submerged submarines. The rights of way of the two perpendicular 14 mile (23 km) overhead transmission lines that constituted the ground dipole antenna which radiated the ELF waves can be seen at lower left. Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz.

The combined effect was to sharpen the transmitted pulse, while reducing 'ringing' in the receiver. In a test in May 1940, Hanbury Brown was able to clearly see the return at a range of , and could still make it out when they approached to 400. Touch, now at RAE Farnborough and having delivered improved versions of ASV, quickly adapted the new oscillator to the existing Mk. III transmitter. Adapting the vertical transmitting "arrowhead", folded twin-dipole antenna design on the nose of the aircraft, from Hanbury Brown's work with the Mk. III eliminated any remaining problems.

Siple Station was a research station in Antarctica (), established in 1973 by Stanford's STAR Lab, to perform experiments that actively probed the magnetosphere using very low frequency (VLF) waves. Its location was selected to be near the Earth's south magnetic pole, and the thick ice sheet allowed for a relatively efficient dipole antenna at VLF (very low frequency – 3 kHz range) frequencies. John Katsufrakis of Stanford University was the "father" of the station and the VLF experiment sponsored by Stanford. There were two stations, Siple I and later Siple II, circa 1979, built above the original which was eventually crushed by the ice.

In comparison, the mass of the first Soviet satellite Sputnik 1 was 83.6 kg (184 lb). The instrument section at the front end of the satellite and the empty scaled-down fourth-stage rocket casing orbited as a single unit, spinning around its long axis at 750 revolutions per minute. Data from the scientific instruments was transmitted to the ground by two antennas. A 60 milliwatt transmitter fed a dipole antenna consisting of two fiberglass slot antennas in the body of the satellite operating on 108.03 MHz, and four flexible whips forming a turnstile antenna were fed by a 10 milliwatt transmitter operating on 108.00 MHz.

For this role, the system used two receiver antennas mounted about one wavelength apart, so that when they were pointed directly at the target the received signals would cancel out and produce a null on the display. This was sent to a second display, whose operator attempted to keep the antennas pointed at the target. The transmitter, which had a power of about 20 kW, was mounted in a large rectangular wooden cabin on a wheeled trailer. The single half-wave dipole antenna was mounted on a short vertical extension at one end of the cabin, with the "line-of-shoot" along the long axis.

As the polarisation of the leaked signal was unpredictable, the detector aerial had to be able to receive mixed or elliptical polarisation. This was achieved with a dipole antenna which was tilted diagonally, placed in front of a metal mesh corner reflector, the whole assembly of which could be rotated. The beam width was narrow enough to give an accuracy of around 5° in locating a source. The complete antenna was large, and permanently mounted on top of a Morris Oxford Traveller estate car, rather than the previous van, so that the overall height of was no more than a typical large van, avoiding height clearance problems.

In contrast to the wide television frequency bands, the FM broadcast band (88-108 MHz) is narrow enough that a dipole antenna can cover it. For fixed use in homes, hi- fi tuners are typically supplied with simple folded dipoles resonant near the center of that band. The feedpoint impedance of a folded dipole, which is quadruple the impedance of a simple dipole, is a good match for 300Ω twin lead, so that is usually used for the transmission line to the tuner. A common construction is to make the arms of the folded dipole out of twin lead also, shorted at their ends.

Animated diagram of a half-wave dipole antenna receiving a radio wave. The antenna consists of two metal rods connected to a receiver R. The electric field (E, green arrows) of the incoming wave pushes the electrons in the rods back and forth, charging the ends alternately positive (+) and negative (−). Since the length of the antenna is one half the wavelength of the wave, the oscillating field induces standing waves of voltage (V, represented by red band) and current in the rods. The oscillating currents (black arrows) flow down the transmission line and through the receiver (represented by the resistance R). Radio waves are radiated by charged particles that are accelerated.

Mounting the receiver in the Heyford was not a trivial task; the standard half-wave dipole antenna needed to be about long to detect wavelengths of 6.7 m. The solution was eventually found by stringing a cable between the Heyford's fixed landing gear struts. A series of dry cell batteries lining the aircraft floor powered the receiver, providing high voltage for the CRT through an ignition coil taken from a Ford. When the system took to the air for the first time in the autumn of 1936, it immediately detected aircraft flying in the circuit at Martlesham, away, in spite of the crudity of the installation.

They introduced new sealing methods and an improved cathode, delivering two examples capable of generating 10 kW of power at 10 cm, an order of magnitude better than any existing microwave device. At this wavelength, a half-dipole antenna was only a few centimetres long, and allowed Lovell's team to begin looking at parabolic reflectors, producing a beam only 5 degrees wide. This had the enormous advantage of avoiding ground reflections by simply not pointing the antenna downwards, allowing the fighter to see any target at its altitude or above it. Through this period, Rowe finally concluded that Dundee was unsuitable for any of the researchers, and decided to move again.

Each antenna element receives power from a separate transmitter module having an output power of 10 kW. The receiving antenna on the right consists of an octagonal array 58 m in diameter consisting of 19,500 crossed dipole antenna elements feeding 4,660 receiver modules. The transmitter module for each antenna element contains a phase shifter which can change the phase (relative timing) of the oscillating current applied to the antenna, under control of the central computer. Due to the phenomenon of interference, the radio waves from each separate transmitting antenna element combine (superimpose) in front of the antenna to produce a beam of radio waves (plane waves) traveling in a specific direction.

The original Siple I station had a four-person winter over crew and the later Siple II station had an eight- person winter over crew. The Siple II station used a 300 kW Kato square wound generator powered by a Caterpillar D353 engine to power the VLF (Jupiter) transmitter which transmitted to a receiver in Roberval, Canada. At the time, the Siple II station had the world's longest dipole antenna. Originally long, it was subsequently increased to and then a second antenna running at 90 degrees was added, resulting in a total antenna length of approximately 50 miles and allowing for phased VLF transmissions.

Marvin P. Middlemark held several patents for his inventions; many were lesser known than his famed Rabbit Ears, such as: a water-powered potato peeler (which failed because when done, a large potato was reduced down to the size of a large marble) and a tennis ball rejuvenator that was designed to bring the bounce back to used tennis balls. In the mid-1960s, NASA turned to Middlemark to develop the technology needed that would allow the original Apollo missions to communicate from the Moon Lander to Mission control. Middlemark was able to solve this problem, unfortunately NASA was not able to use the same theoretical principles of his dipole antenna.

This allows most of the radiation to be concentrated in a narrow main lobe aimed a few degrees above the horizon, which is ideal for skywave transmission. A curtain array may have a gain of 20 dB greater than a simple dipole antenna. Because of the strict phase requirements, earlier curtain arrays had a narrow bandwidth, but modern curtain arrays can be built with a bandwidth of up to 2:1, allowing them to cover several shortwave bands. Rather than feeding each dipole at its center, which requires a "tree" transmission line structure with complicated impedance matching, multiple dipoles are often connected in series to make an elaborate folded dipole structure which can be fed at a single point.

Today Schumann resonances are recorded at many separate research stations around the world. The sensors used to measure Schumann resonances typically consist of two horizontal magnetic inductive coils for measuring the north-south and east- west components of the magnetic field, and a vertical electric dipole antenna for measuring the vertical component of the electric field. A typical passband of the instruments is 3–100 Hz. The Schumann resonance electric field amplitude (~300 microvolts per meter) is much smaller than the static fair- weather electric field (~150 V/m) in the atmosphere. Similarly, the amplitude of the Schumann resonance magnetic field (~1 picotesla) is many orders of magnitude smaller than the Earth's magnetic field (~30–50 microteslas).

SouthPole Site of Subglacial Water (25 July 2018) On May 4, 2005, Mars Express deployed the first of its two 20-metre-long radar booms for the MARSIS experiment. At first the boom didn't lock fully into place;Glitch strikes Mars Express's radar boom - space, New Scientist, May 9, 2005 however, exposing it to sunlight for a few minutes on May 10 fixed the glitch.Mars Express's kinky radar straightened out - space, New Scientist, May 12, 2005 The second 20 m boom was successfully deployed on June 14. Both 20 m booms were needed to create a 40 m dipole antenna for MARSIS to work; a less crucial 7-meter-long monopole antenna was deployed on June 17.

The signal was transmitted from a small vertically oriented half-wave dipole antenna and reflector mounted at the end of a post passing through a hole in the middle of the dish. A coaxial cable carried the signal from the magnetron to the back of the post. Among the parts on the frame were the Type 53 Modulator, which provided pulses of 35 Amps and 10 kV, the Type TR.3151 transmitter, containing the CV64 magnetron, CV43 soft Sutton switch and a crystal mixer, and the Type 50 receiver with its CV67 Sutton tube local oscillator that stepped down the frequency. This left the receiver, time base system and the display inside the aircraft cabin.

At the suggestion of Skinner, they experimented with a parabolic dish reflector behind a dipole antenna on 11 June 1940. They found it offered similar accuracy, but was only deep, easily able to fit within a fighter's nose area. The next day Lovell experimented with moving the dipole back and forth in front of the reflector, and found that it caused the beam to move as much as 8 degrees for 5 cm movement, at which point Lovell regarded "the aerial problem as 75 per cent solved." Follow-up experiments with a production antenna dish from the London Aluminium Company demonstrated the ability to move the beam as much as 25 degrees before it became distorted.

A monopole antenna is a class of radio antenna consisting of a straight rod-shaped conductor, often mounted perpendicularly over some type of conductive surface, called a ground plane. The driving signal from the transmitter is applied, or for receiving antennas the output signal to the receiver is taken, between the lower end of the monopole and the ground plane. One side of the antenna feedline is attached to the lower end of the monopole, and the other side is attached to the ground plane, which is often the Earth. This contrasts with a dipole antenna which consists of two identical rod conductors, with the signal from the transmitter applied between the two halves of the antenna.

In October 2018, the United States Army Research Laboratory publicly discussed efforts to develop a super wideband radio receiver using Rydberg atoms.Army researchers make giant leap in quantum sensing, United States Army Research Laboratory, 2018-10-25 In March 2020, the laboratory announced that its scientists analysed the Rydberg sensor's sensitivity to oscillating electric fields over an enormous range of frequencies—from 0 to 10^12 Hertz (the spectrum to 0.3mm wavelength). The Rydberg sensor can reliably detect signals over the entire spectrum and compare favourably with other established electric field sensor technologies, such as electro-optic crystals and dipole antenna-coupled passive electronics.Scientists create quantum sensor that covers entire radio frequency spectrum, Phys.

The condition for resonance in a monopole antenna is for the element to be an odd multiple of a quarter-wavelength, λ/4. In a dipole antenna both driven conductors must be that long, for a total dipole length of (2N+1)λ/2. The electrical length of an antenna element is, in general, different from its physical length For example, increasing the diameter of the conductor, or the presence of nearby metal objects, will decrease the velocity of the waves in the element, increasing the electrical length. An antenna which is shorter than its resonant length is described as "electrically short" Slyusar V. I. 60 Years of Electrically Small Antennas Theory.

AO-6 (a.k.a. AMSAT-OSCAR 6) was the first Phase 2 amateur radio satellite (P2-A) launched into Low Earth Orbit. It was also the first satellite constructed by the new AMSAT North America (AMSAT-NA) organization. The satellite was launched October 15, 1972, by a Delta 300 launcher from Vandenberg Air Force Base, Lompoc, California. AO-6 was launched piggyback with ITOS-D (NOAA 2). AMSAT-OSCAR 6 was box-shaped, measuring 430mm × 300mm × 150mm, with a mass of 18.2 kg. It had a near-circular polar orbit of 1450 × 1459 km with an inclination of 101.7 degrees. It deployed two quarter-wave monopole antennas, one each for 144 and 435 MHz, and half-wave dipole antenna for 29 MHz.

Although the RUS-1 transmitter was in a cabin on the rear of a truck, the antenna had to be strung between external poles anchored to the ground. A second truck carrying the electrical generator and other equipment was backed against the transmitter truck. Two receivers were used, each in a truck-mounted cabin with a dipole antenna on a rotatable pole extended overhead. In use, the receiver trucks were placed about 40 km apart; thus, with two positions, it would be possible to make a rough estimate of the range by triangulation on a map. The RUS-1 system was tested and put into production in 1939, then entered service in 1940, becoming the first deployed radio-location system in the Red Army.

ERP for FM radio in the United States is always relative to a theoretical reference half-wave dipole antenna. (That is, when calculating ERP, the most direct approach is to work with antenna gain in dBd). To deal with antenna polarization, the Federal Communications Commission (FCC) lists ERP in both the horizontal and vertical measurements for FM and TV. Horizontal is the standard for both, but if the vertical ERP is larger it will be used instead. The maximum ERP for US FM broadcasting is usually 100,000 watts (FM Zone II) or 50,000 watts (in the generally more densely populated Zones I and I-A), though exact restrictions vary depending on the class of license and the antenna height above average terrain (HAAT).

He made a number of back-of-the-envelope calculations demonstrating the amount of energy needed would be impossible given the state of the art in electronics. According to R. V. Jones, when Wilkins reported the negative results, Watt asked, "Well then, if the death ray is not possible, how can we help them?" Wilkins recalled the earlier report from the GPO, and noted that the wingspan of a contemporary's bomber aircraft, about , would make them just right to form a half-wavelength dipole antenna for signals in the range of 50 m wavelength, or about 6 MHz. In theory, this would efficiently reflect the signal and could be picked up by a receiver to give an early indication of approaching aircraft.

312 in) MG 17 and 20 mm MG 151 but replacing the outer wing 20 mm MG-FF cannon with two underwing gun pods containing two 20 mm MG 151/20 each, for a total of two machine guns and six cannon. The A-5/U12 was the prototype installation of what was known as the R1 package from the A-6 onwards. The A-5/R11 was a night fighter conversion fitted with FuG 217 Neptun (Neptune) mid-VHF band radar equipment with arrays of three dipole antenna elements vertically mounted fore and aft of the cockpit and above and below the wings. Flame-dampening boxes were fitted over the exhaust exits. 1,752 A-5s were built from November 1942 to June 1943.

Real (black) and imaginary (blue) parts of the dipole feedpoint impedance versus total length in wavelengths, assuming a conductor diameter of 0.001 wavelengths The feedpoint impedance of a dipole antenna is sensitive to its electrical length and feedpoint position. Therefore, a dipole will generally only perform optimally over a rather narrow bandwidth, beyond which its impedance will become a poor match for the transmitter or receiver (and transmission line). The real (resistive) and imaginary (reactive) components of that impedance, as a function of electrical length, are shown in the accompanying graph. The detailed calculation of these numbers are described below. Note that the value of the reactance is highly dependent on the diameter of the conductors; this plot is for conductors with a diameter of 0.001 wavelengths.

The oldest and most widely used indoor antenna is the rabbit ears or bunny ears, which are often provided with new television sets. It is a simple half-wave dipole antenna used to receive the VHF television bands, consisting in the US of 54 to 88 MHz (band I) and 174 to 216 MHz (band III), with wavelengths of 5.5 to 1.4 m. It is constructed of two telescoping rods attached to a base, which extend out to about 1 meter length (approximately one quarter wavelength at 54 MHz), and can be collapsed when not in use. For best reception the rods should be adjusted to be a little less than 1/4 wavelength at the frequency of the television channel being received.

An ATU can be inserted anywhere along the line connecting the radio transmitter or receiver to the antenna. The antenna feedpoint is usually high in the air (for example, a horizontal dipole antenna) or far away (for example, a ground-mounted monopole antenna used for receiving as well as transmitting). A transmission line, or feedline, must carry the signal between the transmitter and the antenna. The ATU can be placed anywhere along the feedline – at the transmitter output, at the antenna input, or anywhere in between – and if desired, two or more ATUs can be placed at different locations between the antenna and the transmitter (usually at the two ends of the feedline) and tuned so that they create an impedance match throughout the antenna system.

The beam from each array can be deflected up to 60° from the array's central boresight axis, allowing each array to cover an azimuth angle of 120°, thus the entire radar can cover an azimuth of 240°. The building sides are sloped at an angle of 20°, and the beam can be directed at any elevation angle between 3° and 85°. The beam is kept at least 100 ft above the ground over public-accessible land to avoid the possibility of exposing the public to significant electromagnetic fields. Each array is a circle 72.5 ft (22.1 m) in diameter consisting of 2,677 crossed dipole antenna elements, of which 1,792 are powered and serve as both transmitting and receiving antennas, with the rest functioning as receiving antennas.

In an ionized gas plasma antenna, a gas is ionized to create a plasma. Unlike gases, plasmas have very high electrical conductivity so it is possible for radio frequency signals to travel through them so that they act as a driven element (such as a dipole antenna) to radiate radio waves, or to receive them. Alternatively the plasma can be used as a reflector or a lens to guide and focus radio waves from another source.Plasma Antennas: Survey of Techniques and the Current State of the Art D C Jenn, published 2003-09-29, accessed 2010-10-15 Solid-state antennas differ in that the plasma is created from electrons generated by activating thousands of diodes on a silicon chip.

Effective operation on 160 meters can be more challenging than most other amateur bands, because of the overwhelmingly large sizes required for efficient antennas. Full-sized antennas (on the order of a quarter-wavelength or more) are over 130 feet for monopoles, which is also the recommended height for mounting a horizontal dipole antenna, and half-square loops reach nearly 70 feet high. That much real estate may not be feasible for many amateurs, and even with space available, erecting and securing such a large structure is a challenge. The size of the safety zone around an antenna depends on several factors, including the power fed to the antenna, but is roughly 30–40 m (100–130 ft) from the center of the lowest radiating part of the antenna.

In 1894 Righi (along with Indian physicist Jagadish Chandra Bose) was the first person to generate microwaves, producing 12 GHz microwaves with a metal ball spark oscillator, and detecting them with a dipole antenna and spark gap. He used his spark transmitter and detector at wavelengths of 20, 7.5 and 2.5 centimeters (frequencies of 1.5, 4 and 12 GHz) to perform classic optics experiments with microwaves, using quasioptical components, prisms and lenses made of paraffin wax and sulfur and wire diffraction gratings to demonstrate refraction, diffraction, and polarization of these short radio waves, providing experimental confirmation of James Clerk Maxwell's 1873 theory that radio waves and light were both electromagnetic waves, differing only in frequency. His work L'ottica delle oscillazioni elettriche (1897), which summarised his results, is considered a classic of experimental electromagnetism. In 1903 Righi wrote a book on wireless telegraphy.

Conductors, normally metal wires or rods, are cut to a length so that the desired radio signal will create a standing wave of electrical current within them. This means that antennas have a natural size, normally of a wavelength long, which maximizes performance. Antennas designed to receive a given signal will almost always have similar dimensions. Because the antenna size is based on the wavelength, UHF broadcasting can be received with much smaller antennas than VHF while still having the same gain. For instance, Channel 2 in the North American television frequencies is at 54 MHz, which corresponds to a wavelength of 5.5 m, and thus requires dipole antenna about 2.75 m across. In comparison, the lowest channel in the UHF map, Channel 14, is on 470 MHz, a wavelength of 64 cm, or a dipole length of only 32 cm.

Electrically short antennas, antennas with a length much less than a wavelength, make poor transmitting antennas, as they cannot be fed efficiently due to their low radiation resistance. As can be seen in the above table, for antennas shorter than their fundamental resonant length (\lambda/2 for a dipole antenna, \lambda/4 for a monopole, circumference of \lambda for a loop) the radiation resistance decreases with the square of their length. As the length is decreased the loss resistance, which is in series with the radiation resistance, makes up a larger fraction of the feedpoint resistance, so it consumes a larger fraction of the transmitter power, causing the efficiency of the antenna to decrease. For example, navies use radio waves of about 15 – 30 kHz in the very low frequency (VLF) band to communicate with submerged submarines.

55 All LRDG patrols included one vehicle equipped with a Wireless Set No. 11 and a non-military Philips model 635 receiver. The No. 11 Set had been designed for use in tanks, and had transmitter and receiver circuits; the Royal Signals expected to use the No. 11 set to transmit and receive between and with the use of or antennas. The LRDG used Morse code for all transmissions, and were able to transmit over great distances using either a dipole antenna system attached to a rod antenna mounted on the truck, which was adequate up to , or for greater distances, a Windom dipole system slung between two tall poles. The disadvantage of using the Windom system was that it took time to erect and work out the correct antenna length, so it could only be used in a relatively safe area.

"W8XH to Change Wave Length Soon", Buffalo Evening News, May 19, 1934, page 5. A review of W8XH's early operations, written by a WBEN technician, summarized its activities as: Because W8XH was operating under an experimental license, original programming had to be commercial-free. However, programs simulcast from WBEN were allowed to include the original commercials. W8XH underwent a major upgrade in January 1936,"Short Wave Listener: Mechanism of New W8XH Explained" by Earnest H. Roy, Buffalo Evening News, January 11, 1936, page 7. with the installation of a new 100-watt RCA designed transmitter,"W8XH, New High Frequency Station" by R. J. Kingsley, Broadcast News, April 1936, pages 22, 31 (reprinted from Electronics) that fed into a crossed-dipole antenna, known as a "turnstile antenna", that had been developed by RCA's Dr. G. H. Brown.

The best coaxial cable impedances in high-power, high-voltage, and low-attenuation applications were experimentally determined at Bell Laboratories in 1929 to be 30, 60, and 77 Ω, respectively. For a coaxial cable with air dielectric and a shield of a given inner diameter, the attenuation is minimized by choosing the diameter of the inner conductor to give a characteristic impedance of 76.7 Ω. When more common dielectrics are considered, the best-loss impedance drops down to a value between 52–64 Ω. Maximum power handling is achieved at 30 Ω. The approximate impedance required to match a centre-fed dipole antenna in free space (i.e., a dipole without ground reflections) is 73 Ω, so 75 Ω coax was commonly used for connecting shortwave antennas to receivers. These typically involve such low levels of RF power that power-handling and high-voltage breakdown characteristics are unimportant when compared to attenuation.

The AN/FPS-85 radar operates similarly, but has a separate transmitter for each antenna. The AN/FPS-85 radar operates at a frequency of 442 MHz (a wavelength of 68 cm) in the UHF band, just below the UHF television broadcast band, with a 10 MHz bandwidth and a peak output power of 32 megawatts. The radar has separate transmitting and receiving array antennas mounted side-by-side on the sloping face of its transmitter building, pointing south at an elevation angle of 45° (modern phased array radars use a single antenna array for both transmitting and receiving, but at the time it was built this was the simplest design). The transmitting antenna (on the left in the pictures) was a square 72x72 array of 5,184 crossed dipole antenna elements spaced 0.55 wavelength (37 cm) apart, which was later upgraded to 5928 elements.

Due to its image in the ground plane (dotted lines), a monopole antenna has the same radiation pattern over perfect ground as a dipole antenna in free space with twice the voltage In telecommunications and antenna design, an image antenna is an electrical mirror-image of an antenna element formed by the radio waves reflecting from a conductive surface called a ground plane, such as the surface of the earth. It is used as a geometrical technique in calculating the radiation pattern of the antenna. When a radio antenna is mounted above a conductive surface such as the earth, the radio waves directed down toward the surface reflect off it. The radiation received at a distant point is the sum of two contributions: the waves that travel directly from the antenna to the point, and the waves that reach the point after reflecting off the ground plane.

Italian radio pioneer Guglielmo Marconi was one of the first people to believe that radio waves could be used for long distance communication, and singlehandedly developed the first practical radiotelegraphy transmitters and receivers,Hong, Sungook (2001) Wireless: From Marconi's Black-box to the Audion, Chapter 1 & 2 mainly by combining and tinkering with the inventions of others. Starting at age 21 on his family's estate in Italy, between 1894 and 1901 he conducted a long series of experiments to increase the transmission range of Hertz's spark oscillators and receivers. He was unable to communicate beyond a half-mile until 1895, when he discovered that the range of transmission could be increased greatly by replacing one side of the Hertzian dipole antenna in his transmitter and receiver with a connection to Earth and the other side with a long wire antenna suspended high above the ground.Hong, Sungook (2001) Wireless: From Marconi's Black-box to the Audion, p.

Wright's examination led to development of a similar British system codenamed SATYR, used throughout the 1950s by the British, Americans, Canadians and Australians. There were later models of the device, some with more complex internal structure (the center post under the membrane attached to a helix, probably to increase Q). Maximizing the Q-factor was one of the engineering priorities, as this allowed higher selectivity to the illuminating signal frequency, and therefore higher operating distance and also higher acoustic sensitivity. The CIA ran a secret research program at the Dutch Radar Laboratory (NRP) in Noordwijk in the Netherlands from 1954 to approximately 1967 to create its own covert listening devices based on a dipole antenna with a detector diode and a small microphone amplifier. The devices were developed under the Easy Chair research contract and were known as Easy Chair Mark I (1955), Mark II (1956), Mark III (1958), Mark IV (1961) and Mark V (1962).

The first version of the Ju 88C was the C-1 with 20 aircraft converted from A-1 airframes. Some of them entered service in the Zerstörerstaffel of KG 30 which became part of II./NJG 1 in July 1940. The C-1 was followed by the C-2 of which 20 aircraft were converted from A-5 airframes with enlarged wingspan. The C-4 became the first production version with 60 produced and 60 converted from A-5 airframes. The C-6, of which 900 aircraft were produced, was based on the A-4 airframe with more powerful engines and stronger defensive armament (single- or dual-mount belt- fed MG 81 or MG 131 instead of drum-fed MG 15 machine guns). The Matratze 32-dipole antenna for the Lichtenstein UHF radar The C-6 as night fighter was typically equipped with FuG 202 Lichtenstein BC low-UHF band airborne intercept radar, using the complex 32-dipole Matratze antennas. The first four C-6 night fighters were tested in early 1942 by NJG 2. The trials were successful and the aircraft was ordered into production.