So, we need an external antenna for the 802.11b access point, to which the directional antennas of all other users of the wireless network (WLAN) will be oriented. This antenna will have to receive and transmit signals in all directions, so that the network can be accessed from any direction, i.e. must have a circular pattern. In other words, we need external omnidirectional WiFi antenna.
Of course, there are factory solutions for this, but they cost a lot of money, for example, this antenna ANT24-1500 costs 175 USD (Fig. 1)
and this ANT24-0500- 65 USD (Fig. 2)
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And in general they fool our brother and not only in this area, the cost of these products is a penny! Therefore, we will make the antenna ourselves and it will work no worse than the factory ones, since the laws of radio engineering are the same for everyone, and here everything will rest only on accuracy and workmanship.
Our WiFi antenna will be a classic whip antenna with a circular radiation pattern in the horizontal plane, called Ground Plane by radio amateurs, converted to the 2.440 MHz band we need. The antenna is a quarter-wavelength pin with counterweights of the same length, located at 135° relative to the pin.
Why exactly 135°? Because only with these parameters our antenna will have a wave impedance of 50 ohms and will be matched with the 50 ohm cable that feeds it. Here is how the wave impedance changes as this angle changes.
When the antenna mismatches with the cable, not all the energy suitable for the antenna will be radiated by it, i.e. here it will be necessary to observe the manufacturing accuracy. The length of the pin, for the middle of our 2.440 MHz band, will be 27.95 mm (28 mm rounded), the length of the counterweights will be 30.72 mm (31 mm rounded).
Why is the pin shorter than counterweights? Here we observe such a radio engineering rule as a shortening factor, since the length of the radio wave in different media is different. For our antenna with a pin diameter of 2.28 mm, it will be equal to 0.91. It is desirable to maintain the dimensions of the pin and counterweights as accurately as possible, the wave impedance of the antenna also depends on this. It is necessary to try to the flesh to fractions of a millimeter, since at these frequencies the antenna is very small and even a couple of millimeters of discrepancy in size greatly violates the conformity of the length of the quarter-wave pin. It is desirable to make the number of counterweights at least 12, and it is even better to cut a cone from copper foil.
An omnidirectional WiFi antenna is made by releasing the central core of the power cable from the braid, taking into account the required length of the pin.
The counterweights are made of a braid of the same cable twisted and laid to the desired angle. We cut off the upper cover of the cable at a level of 31 mm, remove the braid and shorten the pin to 28 mm. We tin the tip of the pin with a soldering iron so that the wiring of the central core does not disperse and remove the insulation from the central core, since if you leave it, you will need to recalculate the shortening factor, taking into account its influence. All this must be hermetically sealed in a plastic box so that even fresh air does not penetrate.
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Firstly, only about 2 dB is lost here, but we simply don’t have it, secondly, the shortening factor is not taken into account, thirdly, the shape of the connector itself distorts the shape of a theoretically correct antenna of this type.
Since the RF output of all access points usually has an impedance of 50 ohms, we don’t have much choice - the cable must be a characteristic impedance of 50 ohms. Well, of course, a Belden-type H-1000 cable with an attenuation of 0.22 dB / meter would be ideal for us, but we don’t have that kind of money. Therefore, you can choose a cheaper and more affordable RK-50-7-11 with attenuation at our frequencies of about 0.6 dB. Naturally, it should be without joints and damage, preferably new.
Usually all connections in this case are made using special connectors.
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But we don't use it for known reasons. Instead, we take pliers and, without a drop of regret, break the standard indoor WiFi antenna from the access point about 2 centimeters from the bending knee of the antenna.
Be careful, there is a thin cable inside, we will still need it. You pull it out along with a real antenna located inside this case.
Here she is. By the way, it is described in Fig. 4, only to reduce its resistance to 50 ohms, they shortened it to 26 mm, thus making it less effective than a quarter wave antenna.
We unsolder the cable at the base of the antenna pin, pull it out of the tube and cut it in this place. Then we release about a centimeter of the central core from the braid, fluffing it up and bending it back. Next, we release about 4 mm of the central core from the insulation and tin this end with a soldering iron. Now we take a large cable, cut off about a centimeter of the outer sheath, pull back the braid and give the inner insulation the appearance of a cone. Then, with a needle, we try to make a hole between the wires of the core with a depth of 4 mm, preferably closer to the center of the core.
We will stick a core of a small cable into this hole.
And then with a small drop of tin with rosin we solder both cores. We fill the place of soldering with molten insulation material of the central core from some unnecessary piece of the same cable. Next, we connect the braids of both cables on all sides evenly and solder so that there are no gaps, you can add more copper hairs and tin for this or use copper foil. Then we wrap it all with electrical tape and get this.
For all the clumsiness and sloppiness of the product that I made, everything works at a distance of 90 m with a signal level of 61% at a full speed of 11 Mbps.
Considering that the length of my cable is about 8 meters and a friend at the other end of meters has 12 of the same cable with the same connections, feeding a simple canned antenna that has not been brought to mind (for those who are interested, here is an article on a canned Wi-Fi antenna), then I think it's pretty good.
After a year, I bought a smart nokia n95 with wi-fi support and was able to take new measurements.
So, the access point is the same with a power of 15dBm, i.e. 31.6 milliwatts, the nokia n95 wi-fi module has a power of 100 milliwatts, but this is not important, since the communication range will be determined by the lowest power device in the system, i.e. at that distance where the TD hears the Nokia, the Nokia will no longer hear the TD due to its lower power. WiFi antennas in both cases are omnidirectional: on the AP everything is the same as described above, and on Nokia it has a built-in antenna. According to the gps readings, I determined the distances with an accuracy of a couple of meters. Having moved to a distance of 1100 meters, the connection was still stable. From the HTTP server, everything swayed without disruption, Internet access went fine, although the speed was already at a minimum of 1 megabit sec. At a distance of 1200 meters, the connection was already very eager to work, it was impossible. When using more powerful APs such as the DWL-2100AP, it will be possible to communicate over a longer distance.
There was a direct line of sight and without any directional antennas. Although I have a suspicion that in Nokia the antenna has some directivity, although not pronounced - it catches a little better in a vertical position with the left side to the signal source. Of course, the connection will not be good in any place where the phone is turned on, usually on hillocks, the connection may be better in the lowlands.
Instructions for making a "double" Bi-Quad (double figure eight) W-LAN antenna - 2.4 Ghz antennas for wi-fi.
"Double Eight" is a continuation of Bi-Quad, the gain of which is 2 dB higher, i.e. is approximately 12 dB. When building, pay attention to the fact that the copper wires do not touch at the intersections. After construction, it is advisable to varnish the "double eight" to avoid oxidation / corrosion. How important it is to maintain a distance of 15 mm between the reflector and the copper wire is evidenced by the two photographs below:
In order to avoid questions (there were in the first post), consider the construction of an antenna with a circular diagram, in this case something around 270 °.
First, a pipe with a diameter of 70 mm and a height of approx. 100 mm. Then bend a straight 6-element Quad from a copper wire and, using, for example, a bottle, give it an appropriate, curved shape. I repeat for those who do not read very carefully: the distance from the copper wire to the reflector in a circle should be 15 mm! It is important that the crossed wires do not touch each other!
Of course, this is not the only correct option for building such an antenna. The pie antenna can be made larger,
In this case, signal loss in the antenna cable will be minimized.
Ideally, it should look a little different, something like this:
but this is not so important, the main thing is that you can repeat the dimensions by printing. For bending "double eight" - extreme squares are not used. Those who do not have a printer use the following pattern to make a frame: the dimensions are given for a wire with a diameter of 2.5 mm
"Triple Eight" - another continuation of the "Double Eight", the gain coefficient of the "Triple Eight" can be 14 dB or a little more. This is how the painted "triple eight" looks like, in general, not bad:
For beginners! Please note that the posts supporting the antenna at a distance of 15 mm from the reflector must be made of dielectric material!
The "double eight" and the pie antenna discussed above can be mounted together in one housing:
From another.
The antenna is closed. For the manufacture of the protective case, a piece of plastic pipe with a diameter of 125 mm was used, which is used in plumbing, the cover is made of 2 cm plastic. The fixing top nut is made of plastic. You can paint in any color.
I will show you how to assemble a very powerful Wi-Fi antenna that can receive a signal at a distance of many kilometers, but at the same time light and easy to assemble. Having crossed two popular antennas, a wave channel and a pouch antenna, I had the idea to create a Wi-Fi gun.
You can make this antenna from any sheet of metal. I used 0.3mm thick copper foil because it is easy to cut with scissors.
The details of our antenna will be mounted on a hairpin, we need to cut out 7 disks with a hole in the middle.
To do this, you need to place, punch or drill seven holes, and only then circulate the circle. If you do the opposite, then the drill may go to the side, but for us it is important that the hole is exactly in the middle.
We scratch out the circle according to the dimensions indicated in the diagram and cut out our disks.
Picture 1. You need to do it as accurately as possible, the deviation is only a millimeter and it will not work like that. The thickness of the metal and the diameter of the stud have almost no effect on the operation of our blaster and can be anything. It turns out such circles (See Fig. 1) and after all the details are cut out, it remains for us to wind them onto the hairpin, observing the size of the gaps between them.
This irradiator is assembled easily, like a constructor. We install the second plate of our
blaster at a distance as indicated on our diagram - 30 millimeters, by tightening the nuts we select exactly our 30 millimeters.
On the last two disks you need to make a hole for the wire. Our blaster is ready. Now it remains to connect it to our device. At the beginning, it will be a USB modem, then we will connect it to a smartphone, and finally, to a router in order to distribute the Internet through our WI-FI gun.
To connect to a Wi-Fi whistle, you need to carefully disassemble the antenna so as not to damage the wire. We tin the soldering points and solder the wire to the extreme large disk, and the central core to the next one after it. We mount our gun on the bracket so that it is convenient to aim at the victim's router.
The gun catches the net even at a distance of 500 meters. Wi-Fi gun materials are not expensive and available to everyone.
We make a Wi-Fi antenna with our own hands.
Wi-Fi wireless technology has taken over the world. Almost every house and apartment has devices that support this standard. For example, routers (routers) "distributing" a Wi-Fi signal around an apartment or house.
Unfortunately, the power of these devices is not always sufficient to provide more or less acceptable signal strength in all rooms and rooms of apartments, and especially houses. For example, the TP-LINK router I use is located in a corner room and provides for the rooms farthest from it the signal level is almost at the minimum limit. It is not surprising - the signal has to break through four walls.
What to do in such cases in order to increase the level of the Wi-Fi signal of the router to acceptable values ?? That's right, make your own Wi-Fi range antenna.
The network is full of designs of such antennas. More effective are those antennas that can be connected instead of the standard whip antennas of routers.
For me, this option is not suitable. The antenna of my router is non-removable, I don’t want to climb inside the router to solder the cable of a home-made antenna, the router is still under warranty.
Therefore, we find another option - an antenna-nozzle.
This attachment antenna is simply put on the standard whip antenna of the router (router). Nothing needs to be soldered anywhere.
The attachment antenna is a six-element "wave channel", has directional properties. Provides maximum gain in the direction coinciding with the longitudinal axis of the antenna. In addition, the rear radiation lobe is suppressed (reduced) to some extent. The antenna has five director elements and one reflector.
Antenna sketch:
For the manufacture of the traverse, fiberglass with a thickness of 2 mm was chosen.
The standard whip antenna of my TP-LINK router has an irregular geometric shape in cross section, in full accordance with the perverted tastes of modern designers))).
The completed traverse looks like this: 
The radiating elements of the antenna-nozzle are made of copper wire in enamel insulation with a diameter of 0.96 mm. The wire diameter is quite critical and should be within 0.8 ... 0.95 mm, otherwise the antenna parameters will change, and the attachment antenna will be tuned to frequencies different from the frequencies of the Wi-Fi range.
The lengths of the radiating elements must also be maintained with an accuracy of +/- 0.5 mm. The same applies to the spacing between elements.
Antenna elements: 
To install radiating elements in a fiberglass traverse, holes are drilled with a diameter slightly larger than the diameter of the wire elements. I fixed the wire elements with small drops of cyanoacrylate glue.
Antenna assembly looks like this: 
This is how the Wi-Fi antenna installed on the standard antenna of the router looks like: 
To achieve the maximum efficiency of this Wi-Fi antenna, a little adjustment is necessary: the Wi-Fi antenna must be placed at the point where there is a maximum RF current of the standard whip antenna of the router.
To do this, you need to move the Wi-Fi antenna in height, starting from the upper tip of the standard router antenna. Efficiency can be checked either with some field strength indicator, or by checking the signal strength with a tablet, smartphone, etc. in the rooms farthest from the router.
In my case, the most effectively made Wi-Fi antenna works when it is installed 25 mm below the top tip of the standard router pin. This antenna gave an increase of one division according to the signal strength indicator in those rooms where the signal was at the very minimum.
Now many people cannot imagine themselves without the Internet, access points of Wi-Fi networks. To increase the signal strength of the transceivers, both standard and additional antennas are used. Regular antennas in terms of power are from 2 to 9 dBi, approximately. They look like this:
So, we need:
- foil fiberglass, one-sided, 1.5 - 2 mm thick, 220 by 230 mm in size;
- electric jigsaw, with a nail file for metal;
- drill or screwdriver;
- fine sandpaper, metal drills;
- a can of varnish;
- metal sheet, dimensions 270 * 240, thickness 0.5-1 mm;
- a solution of ferric chloride and a container (tray for example).
So step one.
We mark and cut to our size a sheet of fiberglass. We process the edges and clean the surface of the copper side.
A pattern of conductors and vibrators of our antenna will be cut out on the film. To transfer the film to the copper coating of the textolite, for convenience, ask either to immediately stick it on the cutting or to bring a transport (advertising) film with you.
Stage three - gluing the pattern.
Before gluing the film on copper, it is necessary to degrease and allow to dry. Then we take from a sheet of self-adhesive, cut out our pattern at right angles (if there are a lot of them printed), apply an advertising film on it (if not applied at the company). Peel off the protective film and remove the unnecessary part of the pattern, the background. We glue everything that remains on the copper part of the textolite, smoothing and preventing air bubbles from forming. It will turn out like this:
Stage four.
We prepare a container of a suitable size. We dilute ferric chloride, in a proportion of approximately 100 g per 0.5 liter of water, heated to 60-65 degrees Celsius. We dismantle the advertising film. We lower our design, fiberglass to the bottom of the tank. Periodically fidgeting with the workpiece along the bottom of the tank, we wait for the end of the etching of the copper layer. When finished, rinse under running water and wipe dry. It will turn out like this:
