Intro: Easy to Build WIFI 2.4GHz Yagi Antenna. This antenna will extend the range of your WiFi or 2.4GHz devices (like surveillance cameras) into many miles and. The yagi wi-fi antenna design depicted here can be built in just an hour or two, and it works great! It is computer designed, made of wood and wire, and provides high. Security of Wireless Networks Cantenna Exercise. general/pdf/451.pdf. [7]Wikipedia. Yagi WiFi Antenna Author. There are several styles of WiFi antennas with different radiation patterns. point to point network using Yagi antennas. Download the PDF of this reference.
A Yagi-Uda antenna, commonly known as a Yagi antenna, is a directional antenna consisting of multiple parallel elements in a line, [1] usually made of metal rods. [2]. Find great deals on eBay for Yagi Antenna in Computer Directional Antennas. Shop with confidence.
Yagi- Uda antenna - Wikipedia, the free encyclopedia. Drawing of Yagi- Uda VHFtelevision antenna from 1. MHz (USA channels). It has five elements: three directors (to left) one reflector (to right) and a driven element which is a folded dipole(double rod) to match the 3.
The beam direction (direction of greatest sensitivity) is to the left. A three- element Yagi- Uda antenna used for long- distance (skywave) communication in the shortwave bands by an amateur radio station. The longer reflector element (left), the driven element (centre), and the shorter director (right) each have a so- called trap (parallel LC circuit) inserted along their conductors on each side, allowing the antenna to be used at two different frequency bands. A Yagi- Uda antenna, commonly known as a Yagi antenna, is a directional antenna consisting of multiple parallel elements in a line,[1] usually made of metal rods.[2] Yagi- Uda antennas consist of a single driven element connected to the transmitter or receiver with a transmission line, and additional parasitic elements: a so- called reflector and one or more directors.[2][3][4] It was invented in 1. Shintaro Uda of Tohoku Imperial University, Japan,[5] and (with a lesser role played by his colleague) Hidetsugu Yagi.[5][6]The reflector element is slightly longer than the driven dipole, whereas the directors are a little shorter.[4] This design achieves a very substantial increase in the antenna's directionality and gain compared to a simple dipole. Also called a "beam antenna",[4] the Yagi is very widely used as a high- gain antenna on the HF, VHF and UHF bands.[3][4] It has moderate gain which depends on the number of elements used, typically limited to about 1. Bi,[3]linear polarization,[3] unidirectional (end- fire) beam pattern[3] with high front- to- back ratio of up to 2.
The bandwidth of a Yagi antenna, the frequency range over which it has high gain, is narrow, a few percent of the center frequency, and decreases with increasing gain,[3][4] so it is often used in fixed- frequency applications. The largest and most well- known use is as rooftop terrestrial television antennas,[3] but it is also used for point- to- point fixed communication links,[2] in radar antennas,[4] and for long distance shortwave communication by shortwave broadcasting stations and radio amateurs.[2]Origins[edit]The antenna was invented in 1. Shintaro Uda of Tohoku Imperial University, Japan,[5] with a lesser role played by his colleague Hidetsugu Yagi.[6][7]However the "Yagi" name has become more familiar with the name of Uda often omitted.
This appears to have been due to Yagi filing a patent on the idea in Japan without Uda's name in it, and later transferring the patent to the Marconi Company in the UK.[8]Yagi antennas were first widely used during World War II in radar systems by the British, US and Germans.[7] After the war they saw extensive development as home television antennas. Description[edit]. Yagi- Uda antenna with a reflector(left), half- wave driven element (centre), and director(right).
Application Note DN034 SWRA350 Page 3 of 28 3 Board Description The antenna described in this document is a Yagi-Uda commonly named as Yagi and is a. Antenne wifi usb, antenna free wifi hotspot, antenn tv yagi wireless, connexion internet, test debit, mire adsl, accès internet, logiciel wifi, carte wi-fi usb.
Exact spacings and element lengths vary somewhat according to specific designs. The Yagi- Uda antenna consists of a number of parallel thin rod elements in a line, usually half- wave long, typically supported on a perpendicular crossbar or "boom" along their centers.[2] There is a single driven element driven in the center (consisting of two rods each connected to one side of the transmission line), and a variable number of parasitic elements, a single reflector on one side and optionally one or more directors on the other side.[2][3][4] The parasitic elements are not electrically connected to the transmitter or receiver, and serve as passive radiators, reradiating the radio waves to modify the radiation pattern.[2] Typical spacings between elements vary from about 1/1.
The lengths of the directors are slightly shorter than that of the driven element, while the reflector(s) are slightly longer.[4] The radiation pattern is unidirectional, with the main lobe along the axis perpendicular to the elements in the plane of the elements, off the end with the directors.[3]Conveniently, the parasitic elements have a node (point of zero RFvoltage) at their centre, so they can be attached to a conductive metal support at that point without need of insulation, without disturbing their electrical operation.[4] They are usually bolted or welded to the antenna's central support boom.[4] The driven element is fed at centre so its two halves must be insulated where the boom supports them. The gain increases with the number of parasitic elements used.[4] Only one reflector is used since the improvement of gain with additional reflectors is negligible, but Yagis have been built with up to 3. The bandwidth of the antenna is the frequency range between the frequencies at which the gain drops 3 d. B (one- half the power) below its maximum. The Yagi- Uda array in its basic form has very narrow bandwidth, 2 - 3 percent of the centre frequency.[4] There is a tradeoff between gain and bandwidth, with the bandwidth narrowing as more elements are used.[4] For applications that require wider bandwidths, such as terrestrial television, Yagi- Uda antennas commonly feature trigonal reflectors, traps (described below), and larger diameter conductors, in order to cover the relevant portions of the VHF and UHF bands.[9]Yagi- Uda antennas used for amateur radio are sometimes designed to operate on multiple bands.
These elaborate designs create electrical breaks along each element (both sides) at which point a parallel LC (inductor and capacitor) circuit is inserted. This so- called trap has the effect of truncating the element at the higher frequency band, making it approximately a half wavelength in length. At the lower frequency, the entire element (including the remaining inductance due to the trap) is close to half- wave resonance, implementing a different Yagi- Uda antenna. Using a second set of traps, a "triband" antenna can be resonant at three different bands.
Given the associated costs of erecting an antenna and rotor system above a tower, the combination of antennas for three amateur bands in one unit is a very practical solution. The use of traps is not without disadvantages, however, as they reduce the bandwidth of the antenna on the individual bands and reduce the antenna's electrical efficiency and subject the antenna to additional mechanical considerations (wind loading, water and insect ingress). Theory of operation[edit].
A Yagi- Uda antenna for use at 1. MHz (VHF). Consider a Yagi- Uda consisting of a reflector, driven element and a single director as shown here. The driven element is typically a О»/2 dipole or folded dipole and is the only member of the structure that is directly excited (electrically connected to the feedline). All the other elements are considered parasitic.
That is, they reradiate power which they receive from the driven element (they also interact with each other). One way of thinking about the operation of such an antenna is to consider a parasitic element to be a normal dipole element fed at its centre, with a short circuit across its feed point. As is well known in transmission line theory, a short circuit reflects all of the incident power 1. So one could as well model the operation of the parasitic element as the superposition of a dipole element receiving power and sending it down a transmission line to a matched load, and a transmitter sending the same amount of power up the transmission line back toward the antenna element.
If the transmitted voltage wave were 1. Thus a half- wave parasitic element radiates a wave 1. В° out of phase with the incident wave. The fact that the parasitic element involved is not exactly resonant but is somewhat shorter (or longer) than О»/2 modifies the phase of the element's current with respect to its excitation from the driven element.
The so- called reflector element, being longer than О»/2, has an inductive reactance which means the phase of its current lags the phase of the open- circuit voltage that would be induced by the received field. The director element, on the other hand, being shorter than О»/2 has a capacitive reactance with the voltage phase lagging that of the current.[1. The elements are given the correct lengths and spacings so that the radio waves radiated by the driven element and those reradiated by the parasitic elements all arrive at the front of the antenna in phase, so they superpose and add, increasing signal strength in the forward direction. In other words, the crest of the forward wave from the reflector element reaches the driven element just as the crest of the wave is emitted from that element. These waves reach the first director element just as the crest of the wave is emitted from that element, and so on.
The waves in the reverse direction interfere destructively, cancelling out, so the signal strength radiated in the reverse direction is small. Thus the antenna radiates a unidirectional beam of radio waves from the front (director end) of the antenna. Analysis[edit]While the above qualitative explanation is useful for understanding how parasitic elements can enhance the driven elements radiation in one direction at the expense of the other, the assumptions used are quite inaccurate. Since the so- called reflector, the longer parasitic element, has a current whose phase lags that of the driven element, one would expect the directivity to be in the direction of the reflector, opposite of the actual directional pattern of the Yagi- Uda antenna. In fact, that would be the case were we to construct a phased array with rather closely spaced elements all driven by voltages in phase, as we posited. However these elements are not driven as such but receive their energy from the field created by the driven element, so we will find almost the opposite to be true. For now, consider that the parasitic element is also of length О»/2.
Antenne Yagi 1. 4. ANTENNE WIFI YAGI magasin Fréquence Wi. Fi. Catégorie milieu de gamme : Antenne Yagi 1. Utilisation : Le connecteur de l'antenne yagi se visse sur une clé wifi usb, une carte pci, un routeur wifi ou sur n'importe quel dispositif radio fonctionnant sur la fréquence du 2. Ghz. Modèle : Yagi directive. Antenne wifi extérieure et intérieure. Réception et émission sur la fréquence du 2.
Ghz (standard)Gain et angles d'ouvertures : Gain : 1. Wi. Fi : b,g,n. Angles d'ouvertures : H/V : 2. Câble et connecteur : Longueur de câble au choix dans le menu déroulant 1 à 6 mètres.
Connecteur rp- sma mâle (le classique). Installation et fixation : Parfait pour une installation en extérieur car ce type d'antenne yagi est conçue pour résister aux conditions météos les plus difficiles. L'antenne possède une fixation pour mat extérieur ou elle peut être installée sur un support pour antenne wifi.