In mathematics called fractal sets consisting of elements such as the set as a whole. The best example: if we consider the close-close line ellipse, it becomes a straight line. Fractal - how not to approach - the picture will still complicated and similar to the overall look. Elements located bizarre way. Therefore, the simplest example of a fractal assume concentric circles. No matter how much approaching, new circles. Examples of fractals set. For example, Wikipedia given pattern Romanesco cabbage head where the cones consists of exactly resembling drawn head. Now readers will understand that to make fractal antenna is not easy. But interesting.
Why are fractal antennas
Appointment of fractal antenna - to catch more with less victims. In western video - is possible to find a paraboloid, where the transmitter will cut ribbons fractal. There are already doing foil elements of microwave devices that are more powerful than ordinary. We show how to make a fractal antenna end matching and engaged alone with SWR meter. We mention that there is a website, of course, foreign, which promote commercially relevant product, no drawings. Our home-made fractal antenna easier, the main advantage - the design will be able to make their own hands.
The first fractal antenna - biconical - there were, according to the video fractenna.com site, in 1897, Oliver Lodge. Do not look on Wikipedia. In comparison with the conventional dipole pair triangles instead of the vibrator gives an extension strip 20%. Creating a periodic repetitive structure, managed to collect miniature antenna is not worse than the big fellows. Often meet biconical antenna as two frames or fanciful plates.
In the end, it will take more television channels.
If you type a request on YouTube, there is a video on the production of fractal antennas. Better understand the structure of the, if you imagine Star of David of the Israeli flag, in which the angle cut with shoulders. Happened three corners left, two on one side of the place is second to none. Sixth angle absent altogether. Now there are two similar star vertical central angles to each other, the slots left and right, and above them - similar pair. The result array - simple fractal antenna.
Stars of the corners are connected feeder. Pairs columns. Signal is removed from the line, right in the middle of each wire. The construction is collected on the bolts on the dielectric (plastic) substrate of appropriate size. Star side is exactly inch, the distance between the vertical angles of stars (feeder length) four inches horizontally (the distance between the two wires of the feeder) - inch. The stars are at the vertices of the angles of 60 degrees, the reader now draw such as a template, so you do fractal antenna yourself. We made a working sketch, not drawn to scale. I can not vouch that the stars come out exactly, Microsoft Paint without great opportunities for making precise drawings. Enough to look at the image to the fractal antenna device became apparent:
- Brown rectangle shows a substrate of dielectric material. fractal antenna shown in the figure is a chart of a symmetrical pattern. If the shield emitter of interference, the screen is placed on the four stands behind the substrate at a distance of an inch. At frequencies there is no need to place a solid sheet of metal, enough to mesh with the side of a quarter of an inch, do not forget to connect the screen with a braided cable.
- Feeder with 75 Ohm requires coordination. Find or make a transformer that converts 300 ohm 75 ohm. Best Stocks SWR meter and match the desired settings do not touch, and on the device.
- Four stars, arches of copper wire. Lacquer isolation at the place of joining with feeder Strip (if available). Internal feeder antenna consists of two parallel pieces of wire. Good antenna placed in a box for protection against the weather.
Putting a fractal antenna for digital TV
Reading to the end of the review, the fractal antenna will make any. So quickly plunged into the construction, they forgot to tell the polarization. We believe it is linear and horizontal. This stems from reasons:
- Videos obviously American-born, talking about HDTV. Therefore, we can take the fashion of this country.
- As you know, in the world a few States broadcast from satellites using circular polarization, among them the Russian Federation and the United States. Therefore, we believe other data transmission technologies are similar. Why? The Cold War was, we believe, the two countries have chosen strategically what and how to transfer, other countries started from a purely practical reasons. Circular polarization is introduced specifically for spy satellites (moving continuously relative to the observer). Hence the reason to believe that the television and radio broadcasting is observed similarities.
- antenna structure says that linear. There simply have nowhere to take a circular or elliptical polarization. Therefore - if our readers do not have the professionals owning MMANA - if the antenna does not catch in the adopted position, turn 90 degrees to the plane of the radiator. The polarization is changed to vertical. In fact, many will be able to catch and FM, if the size is specified more 4 times. Better wire take thicker (e.g., 10 mm).
Hopefully we explain to the reader how to use the fractal antenna. Couple tips for easy assembly. So, try to find the wire with patent protection. Bend the figure, as shown in the figure. Then the designers differ, be sure to do so:
- Strip the wire feeder and the stars in the field docking. wire feeder for the ears reinforce the bolts on the substrate in the middle parts. In order to perform well in advance, measure inch and draw two parallel lines with a pencil. Along them should go wire.
- Solder uniform design, carefully calibrated distance. The authors recommend making video transmitter to the star corners flat on the feeders, and the opposite ends rested on the edge of the substrate (each in two places). For the stars marked in blue space.
- To fulfill the condition, every star tighten the bolt in one place with a dielectric homutkom (for example, from cambric wires PVA and the like). The figure shows the red attachment points for one star. Bolt schematically traced circle.
The supply cable extends (optional) on the reverse side. Drill a hole in place. Setting SWR conducted by changing the distance between the wire feeder, but it's a sadistic method in this design. We recommend simply measure the antenna impedance. Recall how it's done. It needs oscillator frequency of program watched, for example, 500 MHz, in addition - a high-frequency voltmeter, which are not saved before the signal.
Then the measured voltage output by the generator, for which it is closed on the voltmeter (parallel). Because the variable resistance with the maximum and the smaller self-inductance of the antenna collect resistive divider (connected in series after the generator, first resistance, then antenna). A voltmeter measuring the voltage of the variable resistor, while adjusting the denomination until the reading of the generator without load (cm. paragraph above) will not exceed twice the current. Hence, the denomination of the variable resistor become equal to the characteristic impedance of the antenna at 500MHz.
It is now possible to manufacture a transformer desired. The network is difficult to find the right, for those who like to catch the broadcast found a ready answer http://www.cqham.ru/tr.htm. The site is written and drawn, how to reconcile load with 50 ohm cable. Please note frequencies correspond to the HF bands, NE part fits here. Characteristic impedance of the antenna is maintained in the range 50 - 200 ohms. How will the star is hard to say. If there exists in the household appliance for measuring wave impedance line, recall that if the length of the feeder multiple quarter wavelength, the antenna impedance is transmitted to the output unchanged. For small and large scale such conditions can not be ensured (recall that in particular fractal antenna includes extended range), but for purposes of measuring said fact is used everywhere.
Now readers know all about these amazing transceiver devices. Such an unusual shape suggests that the diversity of the universe does not fit the typical frame.