High Gain Antennas at [ Ссылка ]

1) 0:00 Intro and Unpacking
2) 01:26 How WIFI works
3) 03:04 Antenna Radiation Diagram
4) 03:34 WIFI Antenna Polarization
5) 04:06 Gain and Attenuation
6) 04:53 Empirical Antenna Comparison
7) 05:38 Conclusion

The wifi transmits information using radio waves at the frequency of 2.4 ghz or 5.8 ghz with the band divided into multiple non-reserved channels that is shareable by different networks and therefore subject to interference and drops in performance; so in practice you have to choose the least clogged channel, usually routers do this automatically, and direct the power of the waves exactly where we are interested in coverage.
To cover a medium-sized house, just place the router in the most central point, as high and without obstacles as possible, even if currently mesh networks are able to extend coverage by creating additional access points in absolute transparency for the user. , while to cover areas outside the home it is advisable to use an external antenna, preferably directional.
Radio waves are electromagnetic radiations which according to classical electrodynamics consist of electromagnetic waves formed by synchronized oscillations of electric and magnetic fields that travel at the speed of light in vacuum, while in quantum mechanics the electromagnetic radiation is understood as composed of photons, even if this to choose is to position an antenna in an optimal way, it is not very relevant.
Specifically, the Yagi type antennas, named after one of the two Japanese inventors, commonly used in the reception of television signals, is an antenna composed of a reflector, a dipole and directing elements parallel to each other at about half a wavelength of the optimal frequency to receive fixed along a rod called boom, it has a typical gain from 6 decibels to 20 decibels and a good directivity, proportional to the length of the boom and the number of directors and can be used both in reception and in transmission.
The directional characteristics in the space surrounding an antenna are represented with the radiation pattern which for example for an ideal isotropic antenna is a sphere, as it radiates equally in all directions; so once you replace the omnidirectional antenna of the router with the yagi directional one, you will go from an omnidirectional donut pattern to a lobe pattern, with the larger main one designed to send radio waves mainly in that direction.
Furthermore, to optimize the radio links, the polarization of the antennas must also be considered.
The directions of oscillations of the two fields making up the electromagnetic wave are perpendicular to each other, the orientation of these oscillations is defined as polarization and by convention we refer to that of the electric field; in fact, to ensure that the radio signal induces tensions on the receiving antenna with the maximum possible intensity, the antenna and the radio waves must have the same polarization so as to align the electric field of the radio wave and the length of the antenna element; furthermore, it is necessary to keep in mind both the gain of the antenna which is essentially the ability to concentrate the electromagnetic field in a specific direction, and the propagation of electromagnetic waves which essentially depend on the constitution of the earth's atmosphere and the frequency of the wave.
Furthermore, it is necessary to consider the attenuation due to the reduction of the amplitude caused by the energy transfer of the wave to the propagation medium as a function of the distance traveled in the medium.
Using a web interface of an old wifi router, I check the level of the received signal coming from the ADSL router, about 10 meters away, separated by a floor, comparing the levels reached by the receiving router with the omnidirectional dipole antenna in supplied, without antenna, with a self-made parabolic reflector and a Yagi antenna.
Then I repeat the comparison, but I check the values ​​of the wifi signal using a scanning software for ubuntu on an old netbook, in this case the wifi router acts as an access point.
In both tests the best signals were detected with the omnidirectional antenna and with the self-built parabolic reflector; therefore in the home environment the Chinese Yagi antenna has not proved to be very effective, if instead you need to take the signal out of your home by placing the Yagi antenna outside, it could be useful, always bearing in mind all the aforementioned specifications features.

#wifi #antenna #electromagnetism #polarization

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