Design UWB Hexagonal Fractal Microstrip Non Antenna, or Be Vigilant. DIY fractal antennas Fractal antennas

GP on 160 Minooka

Somehow I got into the hands of an ARRL bulletin in which interesting results of surveys about antennas of the 160 meter range were given. And the main charm, aside from the results, of course, was that this has been a combined statistic since 1969! Firstly, the statistics for such a period must be believed, and secondly, the variety of antenna models at 160 m simply "sticks out". Question one: if you are going to make an antenna for HF today, it will be:
The first answer: 60% - vertical, 30% - horizontal dipole, 10% other options. Verticals in this survey include 1/4, 1/2, 5/8 wavelengths, verticals of random length and inverted L of the antenna. Second question: if today you are going to make an antenna for 160 meters, then it will be: 70% vertical, 17% horizontal, 5% inverted L, 2% H / V combination, 2% invertad V, 3% other options. Isn't it significant? :-)? 70 versus 17! And now, according to the same survey, the arguments for which the respondents made their choice. Answer two: 1. High efficiency in the 160 meter range for DX work. 2. Simplicity of design and ease of setup 3. Low cost 4. Fits in back yard 5. Wide enough bandwidth 6. Works well on long runs 7. Can be reduced for higher frequency ranges. Good scalability.
What's true is true. It is difficult to object to any item on the list. This is probably why the options for vertical antennas for 160 meters are just the sea. How can you navigate this ocean of models and not drown? Based on my little (about 45 years :-) experience, I can give some advice to beginners. I apologize to those who are well versed in antenna theory not to judge me strictly for radical simplifications of concepts. Skip a couple of paragraphs if you're not interested :-)
The first postulate. The antenna must have a physical length of at least approximately a multiple of 1/4 of the wavelength and approximately the same length of counterweights of at least 2. All the shortening schemes (if the electrical length is greater than necessary) and lengthening (in the case of the opposite) serve only one purpose - force the antenna to become resonant. That is, to resonate at the desired frequency. In this case, the efficiency of direct radiation of radio waves will decrease in inverse proportion to the degree of elongation (shortening).
Before deciding to repeat a structure encountered somewhere, you should thoroughly figure out which of the antenna elements are needed to tune into resonance, and which (after that) to ensure the matching conditions. If this cannot be done, then most likely someone described the design created by experience and not the fact that it will work in your conditions. Try to avoid additional elements in the antenna (other than the curtain and counterweights) The best option is when the antenna curtain is 1/4, 1/2 or 5/8 wavelength with the same counterweights. It is quite difficult to place 41 meters of wire (or pipe!) Vertically, so you have to go to the bend (tilt) of the vibrator, which is undesirable in principle, but reduces the radiation efficiency to a much lesser extent than, for example, shortening. Do not forget about such a concept as the effective antenna height. The farther from the ground the top of the antenna (read the longer the rod), the greater this most effective antenna height. The dependence of the field strength at the receiving point is directly proportional to this value. There is one more argument for a longer than a quarter wave length of the pin - the EMF formula induced in the conductor determines the directly proportional increase in the voltage at the antenna connector from the length. Therefore, the best whip antenna is 5/8 waves. But 5/8 for 160 is 100 meters. Even the wealthiest radio amateurs do not often have the opportunity to create a fulcrum (or suspension) at such a height. Even 1/4 wave at this range is 41 meters. But, nevertheless, there is a way to find a compromise for the actual suspension height of a particular user. About half of the modifications and clones of 160 meter vertical antennas follow the principles on which this antenna works. The beauty of the idea is that the user, knowing the height to which he can raise the upper end of the pin, chooses the layout and size of the elements. Of course, the height is limited: no shorter than 2.13 meters for mobile use and no more than 18.29 meters for the base. It's called Minooka Special and looks like this. The table below shows 6 variants of the Minooka overlapping the real possible dimensions (suspension height). In this table, the values ​​of X and Y are uniquely determined, and Z is the maximum possible under the conditions of a repeating design, that is, Z = the height of the suspension point minus X and minus Y. As the inscription under the antenna pattern says, L2 contains from 1 to 20 turns, and L3 from 1 up to 5 turns with a wire with a diameter of 1 mm with a diameter of the coil itself 38 mm. The source (QST, Barry a. Boothe, W9UCW) does not indicate the number of turns L1, but I think that there should be about 20 turns of winding similar to L2 and L3 - winding with a pitch of 3 mm. In the original source, (think 1976!), Americans have already recommended the use of plumbing plastic pipes! And I discovered them only in 2003 :-( In fact, L1 will have to be 100% guessed with this coil, you will tune your pin to resonance at your favorite frequency: it will not work to get a band of 2 megahertz :-( Having found the resonance, you can go to matching. Unlike the source, for tuning I will propose to use an autotransformer - one inductance with the specified winding parameters but only 20 turns with taps. Choosing a tap at which the SWR minimum tuning process can be considered complete.

Having tuned with L1 your segment in resonance at the desired frequency, you can proceed to adjusting the matching with the feeder. To do this, the L3 coil is removed from the circuit and, by changing the L2 coil, the SWR value as low as possible in such a configuration is achieved. Then, returning L3 to the circuit, they achieve SWR equal to one. It is likely that after this you will have to adjust L1. For mobile use (at minimum length) (SWR setting) a good SWR can be obtained without the L3 coil.
It should not be forgotten that in order for the antenna to work effectively, there should be from 2 to 40 radials at the base (according to the author's recommendation :-) just 18.3 meters.
Well? Not tired of lots of variables? But it will work in exact accordance with science :-) Being a pragmatist, I prefer the obvious options and therefore I use a quarter-wave rod with radials without a single coil or matching capacitor. You can see how I did it. However, the same author of Minooka Spec has no trimming options that will work if the dimensions are correct. Well, if you're lying about the fact that capacitive loading is not a tuning element :-)

Three transceivers for 1 antenna

We are all travelers to one degree or another. True, some of us are fanatical travelers. This can be especially said about radio amateurs. Everyone knows the URFF program, the UIA program is known to many, but not all. Even fewer people know about the program, for example, lighthouses. But if in the summer you propose to some homebody to go on a radio expedition to the island and be in demand more than usual (almost a pileup :-), then I think he will agree. I myself really love nature, and when you can combine outdoor recreation and a transceiver at the same time, I'm just happy. At the same time, you forget how much effort was spent on carrying heavy loads,), money for gasoline and nerves to fight the border guards ... (The fact is that all our islands are on the Dnieper, on the border. And border guards are in command of the river).

EN5R-WW 2

In mathematics, sets are called fractal, consisting of elements similar to the set as a whole. Best example: if you look closely at the line of an ellipse, it becomes straight. Fractal - no matter how close - the picture will remain complex and similar to the general view. The elements are arranged in a bizarre way. Consequently, we consider concentric circles to be the simplest example of a fractal. No matter how close, new circles appear. There are many examples of fractals. For example, in Wikipedia, a drawing of a Romanesco cabbage is given, where a head of cabbage consists of cones that exactly resemble a drawn head of cabbage. Readers now understand that making fractal antennas is not easy. But interesting.

Why do you need fractal antennas

The purpose of the fractal antenna is to catch more with fewer victims. In Western videos, it is possible to find a paraboloid where a segment of a fractal ribbon will serve as an emitter. They are already making elements of microwave devices from foil, more effective than ordinary ones. We will show you how to make a fractal antenna to the end, and do the matching alone with the SWR meter. Let us mention that there is a whole site, of course, foreign, where the corresponding product is promoted for commercial purposes, there are no drawings. Our homemade fractal antenna is simpler, the main advantage is that you can make the structure yourself.

The first fractal antennas - biconical - appeared, according to a video from fractenna.com, in 1897 by Oliver Lodge. Don't search on Wikipedia. Compared to a conventional dipole, a pair of triangles instead of a vibrator gives a band expansion of 20%. By creating periodic repeating structures, it was possible to assemble miniature antennas no worse than their large counterparts. You will often find a biconical antenna in the form of two frames or fancy plate shapes.

Ultimately, this will allow more TV channels to be received.

If you type a request on YouTube, a video appears on the manufacture of fractal antennas. You will better understand how it works if you imagine the six-pointed star of the Israeli flag, in which the corner was cut off along with the shoulders. It turned out, three corners remained, two have one side in place, the other does not. The sixth corner is absent altogether. Now we will place two similar stars vertically, with central angles to each other, slits to the left and to the right, above them - a similar pair. The result is an antenna array - the simplest fractal antenna.

The stars are connected at the corners by a feeder. Paired by columns. The signal is removed from the line, exactly in the middle of each wire. The structure is assembled by bolts on a dielectric (plastic) substrate of the appropriate size. The side of the star is exactly an inch, the distance between the corners of the stars vertically (feeder length) is four inches, and horizontally (the distance between the two feeder wires) is an inch. The stars have angles of 60 degrees at their vertices, now the reader will draw a similar pattern in the form of a template, so that he can later make a fractal antenna on his own. We made a working sketch, the scale is not respected. We cannot guarantee that the stars came out exactly, Microsoft Paint without great opportunities for making accurate drawings. Enough to look at the picture to make the structure of the fractal antenna obvious:

1. The brown rectangle shows the dielectric substrate. The fractal antenna shown in the figure has a symmetric radiation pattern. If you shield the radiator from interference, the shield is placed on four posts behind the substrate, an inch apart. At frequencies, there is no need to place a solid sheet of metal, a quarter-inch mesh is enough, do not forget to connect the shield to the cable braid.
2. A 75 Ohm feed line requires matching. Find or make a transformer that converts 300 ohms to 75 ohms. It is better to stock up on a SWR meter and select the desired parameters not by touch, but by the device.
3. There are four stars, bend them out of copper wire. We clean the lacquer insulation at the point of joining with the feeder (if any). The internal antenna feeder consists of two parallel pieces of wire. It is a good idea to place the antenna in a box for protection against bad weather.

Assembling a fractal antenna for digital television

After reading the review to the end, anyone can do fractal antennas. So quickly we got into design that we forgot to talk about polarization. We assume it is linear and horizontal. This stems from considerations:

• The video is obviously of American origin, talking about HDTV. Therefore, we can accept the fashion of the specified country.
• As you know, few states on the planet broadcast from satellites using circular polarization, among them the Russian Federation and the United States. Therefore, we believe that other information transfer technologies are similar. Why? There was a Cold War, we believe, both countries chose strategically what and how to transfer, other countries proceeded from purely practical considerations. Circular polarization is implemented specifically for spy satellites (moving constantly relative to the observer). Hence, there is reason to believe that there is a similarity in television and radio broadcasting.
• The antenna structure says it is linear. There is simply nowhere to take circular or elliptical polarization. Therefore - if only there are no professionals among our readers who know MMANA - if the antenna does not catch in the accepted position, turn it 90 degrees in the plane of the emitter. The polarization will change to vertical. By the way, many will be able to catch FM, if the dimensions are set more times in 4. It is better to take a thicker wire (for example, 10 mm).

We hope we have explained to the readers how to use the fractal antenna. A couple of tips for easy assembly. So, try to find a wire with varnished protection. Bend the shapes as shown in the picture. Then the designers disagree, we recommend doing this:

1. Strip the stars and wires of the feeder where they join. Fasten the feeder wires by the ears with the bolts on the base in the middle parts. To do this correctly, measure an inch in advance and draw two parallel lines with a pencil. Wires should lie along them.
2. Solder a single structure, carefully checking the distances. The authors of the video recommend making an emitter so that the stars lie flat on the feeders at their corners, and with their opposite ends resting on the edge of the substrate (each in two places). For an approximate star, the locations are marked in blue.
3. To fulfill the condition, pull each star in one place with a bolt with a dielectric clamp (for example, PVA wires from cambric and the like). In the figure, the attachment points are shown in red for one star. The bolt is schematically drawn with a circle.

The power cable is (optional) routed from the back. Drill holes in place. The VSWR is adjusted by changing the distance between the wires of the feeder, but in this design it is a sadistic method. We recommend that you simply measure the characteristic impedance of the antenna. Let us recall how this is done. You will need a generator for the frequency of the program being watched, for example, 500 MHz, in addition - a high-frequency voltmeter, which will not save in front of the signal.

Then the voltage produced by the generator is measured, for which it is closed to a voltmeter (in parallel). From a variable resistance with an extremely low self-inductance and an antenna, we assemble a resistive divider (we connect in series after the generator, first the resistance, then the antenna). We measure the voltage of the variable resistor with a voltmeter, while adjusting the value until the generator readings without load (see paragraph above) become twice the current. This means that the value of the variable resistor has become equal to the characteristic impedance of the antenna at a frequency of 500 MHz.

It is now possible to manufacture the transformer as desired. It is difficult to find what you need on the network; for those who like to catch radio broadcasting, they found a ready-made answer http://www.cqham.ru/tr.htm. The site has written and drawn how to match the load with a 50-ohm cable. Please note that the frequencies correspond to the HF range, the CB fits here partially. The antenna characteristic impedance is maintained in the range of 50 - 200 Ohm. How much the star will give is difficult to say. If there is a device on the farm for measuring the wave impedance of the line, recall: if the length of the feeder is a multiple of a quarter of the wavelength, the antenna impedance is transmitted to the output unchanged. For a small and large range, such conditions cannot be provided (recall that, in particular, fractal antennas include an extended range), but for measurement purposes, this fact is used everywhere.

Readers now know all about these amazing transceiver devices. Such an unusual shape suggests that the diversity of the universe does not fit into the typical framework.

As we discussed in previous articles, fractal antennas have been found to be about 20% more efficient than conventional antennas.This can be very useful for the application. Especially if you want your own TV antenna to pick up a digital signal or high definition video, to increase the range of cell phones, Wi-Fiband, FM or AM radio, and so on.

Most cell phones already have built-in fractal antennas. If you've noticed in the past few years, mobile phones no longer have antennas on the outside. This is because they have internal fractal antennas engraved on the PCB, allowing them to receive better reception and pick up more frequencies like Bluetooth, cellular and Wi-Fi all from the same antenna at the same time!

Information from Wikipedia: "A fractal antenna differs markedly from a traditional antenna design in that it can operate with good performance at a wide variety of frequencies at the same time. Typically, standard antennas must be" cut "at the frequency for which they are to be used and thus Thus, a standard antenna only works well at that frequency, making fractal antennas an excellent solution for broadband and multiband applications. "

The trick is to create your own fractal antenna that resonates at the frequency you want it to be. This means it will look different and can be calculated differently depending on what you want to get. A little math and it will become clear how to do this. (You can also limit yourself to an online calculator)

In our example, we will make a simple antenna, but you can make more complex antennas. The harder the better. We'll use the 18 gauge solid wire coil needed to build the antenna as an example, but you can go further by using your own etching boards to make the antenna smaller, or more complex with higher resolution and resonance.

(tab = TV Antenna)

In this tutorial, we will try to create a TV antenna for a digital signal or a high definition signal transmitted over a radio channel. These frequencies are easier to work with, with wavelengths at these frequencies ranging from half a foot to several meters in length for half the wavelength of the signal. For UHF (decimeter waves) circuits, you can add a director or reflector which will make the antenna more directional. VHF (VHF) antennas also depend on direction, but instead of pointing directly at the TV station, the "ears" of dipole VHF antennas must be perpendicular to the waveform of the TV station transmitting the signal.

First, find the frequencies you want to receive or broadcast. For TV, here is the link to the frequency graph: http://www.csgnetwork.com/tvfreqtable.html

And to calculate the size of the antenna, we will use an online calculator: http://www.kwarc.org/ant-calc.html

Here's a good PDF of design and theory:download

How to find the wavelength of a signal: wavelength in feet = (coefficient of the speed of light in feet) / (frequency in hertz)

1) Coefficient of the speed of light in feet = +983571056.43045

2) Coefficient of the speed of light in meters = 299792458

3) Factor of the speed of light in inches = 11802852700

Where to start: (VHF / UHF dipole array with reflector that works well for a wide range of DB2 frequencies):

(350 MHz - a quarter of an 8-inch wave - a 16-inch half-wave that falls in the microwave range - between channels 13 and 14, and which is the center frequency between the MV-UHF range for better resonance). These requirements can be changed to work better in your area, as your distribution channel may be lower or higher in the group.

Based on the materials on the links below ( http://uhfhdtvantenna.blogspot.com/ http://budgetiq.wordpress.com/2008/07/29/diy-hd-antenna/ http://members.shaw.ca/hdtvantenna/ and http: // current .org / ptv / ptv0821make.pdf) , only fractal designs allow us to be more compact and flexible and we will use the DB2 model, which has a high gain and is already quite compact and popular for indoor and outdoor installations.

Basic costs (cost about $ 15):

1. Mounting surface such as a plastic case (8 "x6" x3 "). http://www.radioshack.com/product/index.jsp?productId=2062285
2. 6 screws. I used self-tapping screws for steel and sheet metal.
3. Matching transformer 300 ohms to 75 ohms. http://www.radioshack.com/product/index.jsp?productId=2062049
4. Some 18 gauge solid wires. http://www.radioshack.com/product/index.jsp?productId=2036274
5. Coaxial RG-6 with terminators - limiters (and rubber sheath, if mounted outside).
6. Aluminum when using a reflector.
7. Sharpie marker or equivalent, preferably with a fine tip.
8. Two pairs of small pliers are needles.
9. The guide is at least 8 inches.
10. Protractor for measuring the angle.
11. A drill and drill bit that is smaller in diameter than your screws.
12. Small pliers.
13. Screwdriver or screwdriver.

NOTE: HDTV / DTV editing to PDF http://www.ruckman.net/downloads-1#FRACTALTEMPLATE

Step one:

Assemble the housing with reflector under the plastic cover:

Step two:

Drill small threaded holes on the opposite side of the reflector in the following positions and place the conductive screw.

Step three:

Cut four 8 "pieces of solid cored wire and expose it.

Step four:

Using a marker, mark every inch on the wire. (These are the places where we're going to bend)

Step five:

You must repeat this step for each wire. Each bend on the wire will be equal to 60 degrees, thus a fractal is obtained. Resembling an equilateral triangle. I used two pairs of pliers and a protractor. Each bend will be 1 "division. Make sure you visualize the direction of each bend before doing this! Use the diagram below for guidance.

Step six:

Cut 2 more pieces of wire at least 6 cm in length and expose them. Bend these wires around the top and bottom screws, and tie to the center of the screw. Thus, all three come into contact. Use wire cutters to cut off unwanted parts of the wire.

Step seven:

Place and wrap all your fractals in the corners with screws

Step eight:

Attach the matching transformer through the two screws in the center and tighten them down.

Ready! You can now test your design!

As you can see in the photo below, every time you split each section and create a new triangle with the same wire length, it can fit in less space, taking up space in a different direction.

Translation: Dmitry Shakhov

Below you can watch a video on creating fractal antennas (eng.):

(tab = Wi-Fi antenna)

Earlier I had heard about fractal antennas and after a while I wanted to try to make my own fractal antenna myself, in order to try this concept, so to speak. Some of the advantages of fractal antennas described in research papers on fractal antennas are their ability to efficiently receive multiband RF signals, given their relatively small size. I decided to create a prototype of a fractal antenna based on a Sierpinski carpet.

I designed my fractal antenna with a connector compatible with my router Linksys WRT54GS 802.11g. The antenna has a low profile gain design and in preliminary testing at a distance of 1/2 km from the WiFi Link hotspot with several trees along the way, it showed quite good results and signal stability.

You can download a PDF version of the Sierpinski carpet antenna template that I used, as well as other documentation from these links:

Making a prototype

This is a photo with a ready-made prototype of a fractal antenna:

I attached Linksys WRT54GS RP-TNC connector to fractal antenna for testing

When I designed my first prototype of a fractal antenna, I was worried that the triangles might become isolated from each other on the PCB during the etching process, so I expanded the connections between them a little. Note: Since the final transition of the toner finished more accurately than I expected, the next version of the fractal antenna prototype will be presented with thin contact points between each of the fractal iterations of the Sierpinski triangle. It is important to make sure that the elements of the Sierpinski carpet (triangles) are in contact with each other and the connection points should be as thin as possible:

The antenna design was printed on a Pulsar Pro FX laser printer. This process allowed me to copy the antenna design onto the copper-clad PCB material:

The laser printed antenna design is then transferred to the copper sheet of the printed circuit board by a thermal process using a modified laminator:

This is the copper PCB material after the first step of the toner transfer process:

The next necessary step was to use the Pulsar Pro FX "Green TRF Foil" on the PCB. Green foil is used to fill in any toner gaps or unevenly thickened coatings in toner transfer:

This is a cleaned board with an antenna design. The board is ready for etching:

Here I masked the back of the PCB with electrical tape:

I used the ferric chloride direct etch method to etch the board in 10 minutes. The direct etching method is carried out with a sponge: it is necessary to slowly wipe the entire board with iron chloride. Due to the health risks associated with the use of ferric chloride, I have worn safety goggles and gloves:

This is the post-etched board:

I wiped the circuit board with a swab dipped in acetone to remove the toner transfer coatings. I used gloves when cleaning because acetone will absorb through typical latex disposable gloves:

I drilled a hole for the antenna connector using a drill and drill:

For my first prototype, I used the RP-TNC connector from standard Linksys router antennas:

Close-up of Linksys - RP-TNC Compatible Antenna Connector:

I applied a little water to the PCB at the soldering point just before soldering:

The next step is to solder the wire from the RP-TNC connector to the base of the Sierpinski antenna on the PCB:

Solder the second wire of the antenna connector to the plane of the PCB board:

The antenna is ready to use!