Choosing a structure based on the destination and the frequency range. The range of VHF and HF are profitable pieces of copper wire, called vibrators in the scientific world. There are quarter-wave and half-wave. The first are good that the small size, the latter known for certain broadcast reception. That spinning engineers, choosing the lesser of two evils: to fit the antenna in a given area, to establish reliable, so to maximize reception. And changing the structure, for example, on the Wi Fi and slightly lower frequencies used square antenna with contact pads that are combined into a lattice. This design already at 800 MHz would be great, and increased manufacturing complexity. Not have to see that the antenna to give his own hands built under this scheme.
Antennas for questioning
Lack of internet for many is a limitation. The townsfolk today earn, play and communicate online. But the cable internet in the country, probably can not be done. Rather, it is a cellular modem, rarely Wi Fi.
The difference in size of structures exclusively. Wireless protocols use a vertical linear polarization, takes many types of antennas. Commonly used:
- Where the signal is relatively high, but would like to improve the quality, often used quarter-vibrators are usually the vertical line of the coaxial cable, free from the screen. The characteristic impedance of 50 ohm line is taken.
- Loop antennas are proposed for television, but with the advent of digital radio amateurs quickly realize that biquadrate if specially designed for Wi Fi and 3G. Therefore homemade antennas are popular today. They simply make his own, marked, and other advantages. First of all, a relatively high gain. If the quarter-vibrator deprived preferred direction, then biquadrate no longer will provide omnidirectional. Placed behind the screen protects against interference and provides additional reinforcement. Because of these qualities loop antennas Kharchenko popular.
- The above-mentioned antenna radiators on the square has been repeatedly discussed and popular in Russia. It limits the process no explanatory guidelines for the creation of similar products. They have a complex configuration, and the slightest deviation from the specified dimensions causes multipath waves, which adversely affects the general functioning of the product. The product is characterized scalability (easily transferred from one frequency to others), the possibility of assembling the more complex structures on the basis of elementary squares. We did not observe that TV antenna is designed to give on the basis of these elements. We assume that this is possible, but complications with the manufacture of the mass.
- We assume that the manufacture and manage wave channel frequencies for digital communications, but such a solution is not practical as the production log-periodic antennas. Note the difference with the loop antenna proposed for television (and in those days prophesied for 300 MHz), and then migrated to the fans of online games. We believe that the matter of complexity of manufacture. Yagi and collect difficult for TV that talk about the tiny elements that require precise adjusting to each other. This added complexity of coordination. Apparently, considering aspects of amateur radio operators did not dare to experiment in the microwave region.
TV antenna to give
TV antennas have the form of letter T. Designed for horizontal polarization, much different from the radio. Television broadcasts are usually on the meter and decimeter waves, and the size of the vibrator is relatively small. Fastened horizontally on the mast. Spacers are not put just one piece of pipe is welded to another. Vibrator used often symmetrical. Operate both halves - the first signal goes to the core, the second - on the braid.
If you allow the possibility, it is better to make the antenna to give a half-wave dipole. There is no need (for the television) to harmonize it with the cable. More precisely, the requirements are mitigated, if compared with the quarter-wave. In a range of commonly used TV channels and wave log-periodic antenna. Unlike WiFi, 3G, where the broad band is not required, a number of TV reception antennas cover a considerable range, reaching, at times, hundreds of megahertz. It is understood that the agreed appointment in this case is difficult, the design complexity increases. Please note, all in the modern world tends to simplify. We know that by 2017 Russia plans to switch to digital broadcasting.
Unlike the new standard is that the channels are multiplexed on a single frequency. Construction of antennas is simplified. The same frequency parameters is easier to calculate, it makes no sense to complicate the details. Suitable ordinary half-wave or quarter-wave vibrator, similar to the letter T on the roof.
Multiple channels can feel a kind of environmental discharge protection. Life in big cities is difficult, background radiation is not the most favorable. Radio waves do not bring a person good, transmitter power is limited by law. Not to mention the additional payment for domains. If the channels are collected at the same frequency, eliminating the other and closing the broadcasting background will be more favorable. The same happens if the provider will remain a single provider.
- How to make the antenna for multiplex. First, you can use the advice of experienced networkers and provide a prefix scrap of coaxial cable a quarter of a wavelength. Scraped braid, wire itself is turned in 90 degrees and soldered connector. length of cable is stuck horizontally. In case of poor reception change an angle of 90 degrees on the other, amplifies the signal. Ideally, the receiving antenna is perpendicular to the wave front. It is not always achieved arbitrary location.
- Even in the course of the loop antennas, although pushed back wave channel (and log-periodic antennas). Dignity that biquadrate flat, easy to hide under the lining of vinyl siding. The appearance of a country house does not suffer, and thieves do not utaschat antenna winter. like antenna calculation has already been given, but remember how to do it.
To make biquadrate, find the broadcast frequency and polarization of the wave. In the case of multiplex complexities arise. For example, the frequency of 650 MHz, this value is found from the wavelength obtained 299792458/650000000 = 461.2 mm. Biquadrate looks like a figure eight, but in the center there is no intersection. The edges converging at a distance of 1 mm and diverge again. In this case, eight standing upright, all the angles straightening. It looks like two squares, first standing on one of the corners, the second - from the top, as well. Because the antenna is called biquadrate, but in scientific terms should be called loop antenna Kharchenko. The design proposed in 1961 for television.
Found wavelength. side of the square is equal to a quarter, 115.3 mm. This design is easy to fit on the parcel box, it will provide the back side screen. The distance to the fourth power of the screen is 0.175 wavelength. For this case 80.71 mm. Weighty distance. You have to find two racks of hard rubber or other dielectric. They emitter located. It is allowed to apply, and three counters, and four in place.
The output signal is conducted to place sides of closest approach (where suited to each other at a distance of 1 mm). The first closes the screen is removed from the second signal. Add that the wire thickness is chosen proportional to the frequency. 650 MHz - 11 mm. You can take the lead and thinner. It is desirable to find a circular cross-section wire. Since copper is likely to encounter difficulty and razdobudete steel or aluminum. It is clear that iron arch shape is difficult, and the loss in metal thickness are significant, antenna amplifier for the villa to help cope with the disaster.
As an option, people put a plate. Through it receive TV and internet. And mobile operators are everywhere. Requests sent by mobile, and the answer comes from the satellite. packet download speed is negligible, but the needs of the small suit.
