Homemade antennas for a cell phone. How to strengthen the cellular signal on your phone with your own hands

Despite the widespread use of mobile communications, the question of how to strengthen the signal of the phone, or rather the cellular connection to which it is connected, is still relevant. It doesn't matter if you live in a small village or in a metropolis, the likelihood that your device will stop picking up a signal is everywhere.

Operators are gradually solving this problem, new base stations appear, and communications are increasing. What if the problem lies with your phone and not the network? Today we decided to figure out what the bad signal level is connected with and whether it is possible to fix it with our own hands.

What is Cellular Signal?

The principle of cellular communication is quite simple: there is a base station of the operator and your phone, a radio frequency channel is organized between them, through which SMS messages are transmitted, calls are made, data is exchanged on the Internet.

There are several standards for cellular communication, differing in the way the signal is transmitted and the frequency. Typically, base stations are erected at higher elevations in order to maximize coverage. However, you can't get away from the obstacles that impede the passage of the signal. These can be walls, trees, and other obstacles, upon contact with which the signal weakens.

It is clear that in an open area where high-rise buildings do not abound, the coverage area will be higher. For example, for stations operating according to the GSM-900 standard, in this case, the zone is no more than 30,000 kilometers. In urban areas, the figure is reduced to 7 kilometers. Stations with more advanced communication standards, such as 3G and LTE, cover an area that is half the diameter.

Why do we have a weak phone signal?

Due to the above mentioned barriers, so-called dead zones or holes in the coating can form. That is, places where the signal is weak, unstable or completely absent. Where people most often encounter a bad signal level on the phone:

• places located at a significant distance from the nearest station (there is simply no coverage);
• basements, underground parking lots, lowlands (the signal cannot simply penetrate here);
• hills, skyscrapers (often “to rise higher” does not mean the presence of a signal - above the 12-14th floor there is often no signal at all);
• buildings made of metal structures that do not transmit a signal.

However, obstacles and remoteness from the station are not always the reason for the lack of a signal. Often the reason is the user's phone. You have probably been in situations where a friend has a cellular signal, but you do not.

And at the same time, you use the services of one operator. It is common for two identical phones to have different signal levels. There can be many reasons:

• a phone in a metal case or in a metal case can catch the network much worse than a plastic device;
• quite often, no matter how surprising it sounds to you, the reason is the "clumsy" firmware of the phone;
• damage to any components as a result of falls, immersion in water, and so on;
• the phone may have a defect in the antenna from the factory, which is especially the case with Chinese manufacturers of inexpensive models.

How to amplify a phone signal with your own hands?

Well, let's go over the theory, let's move on to practice. We will analyze several ways to amplify a cellular signal, from the simplest to the most complex and expensive.

The reason is the firmware

It is worth starting with checking the correctness of the software before trying to get to the insides of the phone. Hundreds of users face the deterioration of the communication signal after flashing, so attention should be focused.

We have already written, so we will not repeat ourselves. Firmware is a fairly simple process, but with its own nuances. Just remember to back up your important files.

If the flashing helped, then we congratulate you, if the phone still does not catch the network well, then move on to the next point.

The signal is poorly picked up due to damage to the phone

As already noted, the phone often picks up the signal poorly after accidentally falling on a tile or plunging into the sea. In this case, the average user has no choice but to go to the service center.

Modern phones are rather complex devices, so most people cannot identify the source of the problem on their own. It is likely that specialists will detect damage and carry out the necessary work so that your phone can again cope with the network search without any problems.

How to amplify a phone signal with your own hands

In most cases, the reason for a weak cellular signal lies in a defect in the antenna, which, in fact, is responsible for this function. Often, owners of inexpensive smartphones from the Middle Kingdom are faced with the fact that the manufacturer cheated a little by loosely connecting the antenna to the motherboard of the device. You can correct the mistake yourself, but you need at least a little understanding of how the phone works. Otherwise, we contact the service center with a description of the problem.

1. today smartphones are represented by a very different design, therefore, they are disassembled in different ways; the easiest way to get to the insides of a phone with a removable cover and a battery is more difficult when the smartphone is not separable;

Do not hurry... Before starting the disassembly, find a video or text material on the Internet that will show and tell you how to disassemble your particular device, what you should pay attention to.

Please also note: after disassembling your smartphone, you lose your warranty.

1. as a rule, the antenna is hidden in the lower or upper part of the case, represented by small copper strips (again, for the location of the antenna specifically in your model, see the corresponding materials);
2. after you get to the board, you will find several spring contacts, which should fit snugly to the ribbon cable located on the back of the structure;
3. if the spring contacts of the motherboard do not fit well with the ribbon cable, carefully correct them using, for example, tweezers;
4. assembling the phone and enjoying a good network signal.

We connect a homemade antenna to the phone to amplify the signal

The above methods only work if the problem lies with your phone. But, as we noted at the beginning of the material, the cause of a bad signal can be various kinds of obstacles or a significant distance from the station. In this case, you can try to amplify the antenna of our device with just a piece of wire.

Immediately, we note that this method is not suitable for all phones. The fact is that for its implementation, a special diagnostic port is required, which is difficult to reach in a modern non-separable smartphone (in a number of models it cannot be found at all). It looks like a small round-shaped connector in golden color.

take a small piece of thin insulated wire;

insert into the connector;

we put it so that it does not interfere with other components and the closure of the lid.

Everything, as practice shows, the signal of the telephone network is greatly enhanced. Isn't it amazing ?!

Some users inserted a piece of wire into the 3.5 mm port (under the headphones). Sometimes it works too.

Sticker or foil to enhance phone signal

In the vastness of foreign online stores, it will not be difficult to find a bunch of different devices for signal amplification. Among them, a small sticker-sticker is popular, which is a few metal tracks, which, according to the manufacturer, allow you to get rid of interference.

Similar stripes can be seen in some smartphones by default, so the “magic” properties of the sticker have a right to life.

However, to achieve a slight improvement in the signal, according to a considerable number of users, a piece of ordinary foil will help. It is located under the phone cover, closer to the antenna. The method is simple, so you can try.

Strengthening communication using a repeater

In some cases, when the signal cannot be amplified by any of the methods (too thick walls of the room, remoteness from the base station), they resort to using special antennas or repeaters. Such devices can significantly enhance the signal, but their cost often scares off a potential buyer.

Where to buy cheap?

You can build something similar with your own hands, but often it does not amplify the signal at all or does it very, very badly.

For example, some people use the following method:

1. we take a metal rod (50 cm is enough), a coaxial cable, a piece of foil (about 10x4 cm) and plywood or plastic;
2. we bend the metal rod so that we get a rhombus-shaped structure;
3. glue the foil to the plywood;
4. the metal rhombus and the foil are connected by means of a coaxial cable (soldered);
5. the end, on which the rhombus turned out to be, we raise it higher, the other, with the foil, we leave it at the bottom;
6. we bring the phone to the foil to check the signal quality.

You will probably need to find the most suitable place for the resulting structure to pick up the signal.

It is clear that such an amplifier is unlikely to provide communication for a large company that is not lucky enough to have an office in an area without network coverage. Here you will already have to seek help from specialists. Today, many companies provide such services, and not only will offer modern equipment, but will also be engaged in installation.

By the way, it is not worth saving on specialists - for installation, workers use special devices that help determine the most suitable place, select frequencies, and so on. An ordinary user, of course, will find it difficult to cope with such a task.

Recently, the coverage area of ​​GSM 900 networks in Russia has significantly increased. Nevertheless, the situation is far from ideal. If in European countries the problem of uncertain reception is practically absent, then the majority of domestic users often encounter it - in country houses, in summer cottages, etc. And how wonderful it would be to go fishing, hunting, to the countryside, without losing contact with the outside world !

The key to solving this problem is external directional or omnidirectional antennas. True, buying an antenna is not enough - you need to install and configure it correctly. Readers familiar with radio electronics will be able to independently manufacture and configure an antenna operating in the GSM standard. Today we will talk about the types of antennas and how to install and configure them.

reference

Quite simply, a mobile phone is a duplex radio station that communicates at different frequencies. There are 124 frequencies in the GSM 900 standard. The phone, like the base station, can operate on any frequency determined by the operator.

The base station (BS) transmits and the telephone (MS) receives on the frequencies 935.2 - 959.8 MHz. The mobile phone transmits and the base station receives at the frequencies 890.2 - 914.8 MHz. The channel from BS to MS is called Down Link, from MS to BS - Up Link. Most operators use the limitation of the range of the mobile phone from the base station - 35 km, which is due to the peculiarities of the standard. Let us explain that in a network of standard configuration, 8 time intervals (time slots) are formed in one frequency channel: one service, and seven - conversational. It is in this case that the maximum communication range on each channel is 35 km. However, GSM also provides for a non-standard cell configuration, in which the communication range is increased by 70 - 100 km (Extended Cell configuration). Unfortunately, with this configuration, the number of conversation channels is reduced to 2 - 3, which reduces the capacity of the network. It is not profitable for the operator to use this mode in the city and near the operator. This mode is sometimes used at seaside to create coastal coverage.

Thus, if you have a GSM 900 phone, do not try to establish a connection by moving more than 35 km from the nearest base station. The maximum communication range reached by me is 34 km.

Communication range

The following factors affect the radio communication range:

BS and MS location and terrain.

MS power and sensitivity.

BS power and sensitivity.

Antennas used on MS and BS.

The will of the Lord God (experienced signalmen joke that this is the main thing).

Typically base stations have a power of 20 - 30 watts. Antennas are used either whip or directional. The sensitivity of base stations is -100 dB - 115 dB. The user, of course, cannot change or influence all these parameters. The phone's output power is 0.3 - 2 W, the sensitivity is 90 - 105 dB. The sensitivity of a phone is mainly determined by the technology used to create low noise input devices. If in areas of reliable reception the difference in sensitivity and power between the models is almost invisible, then in the area of ​​uncertain reception it can become critical. Often the handset shows the signal level from the base station 1 - 2 cubes (on a scale), but cannot establish a connection: there is not enough power. Although ETSI standardization regulates the standard output powers for each class of phones, the actual value may fluctuate slightly. SAGEM, Alcatel, Motorola handsets have good sensitivity. And in terms of power, all old phones, especially Motorola, pass by. All Phase 2 phones have roughly the same wattage.

As for the relief, on flat terrain and along the river, waves propagate better. The higher you are (within reason), the better the signal. The forest sometimes "dampens" the waves more than urban development.

Signal search

So, you've got out of town and want to provide yourself with a connection. Climb to the roof, attic, or the highest point near your home or location. If the phone picks up the network, but at the limit (or unstable), you have every chance to improve the situation using an external antenna. If the distance to the station is less than 30 km, and the network is not being caught, also try using an antenna. In the latter case, try to negotiate with the vendor to return the antenna if the experiment fails.

If the signal, albeit very weak, was still caught, dial any city number to check. If during a conversation the audibility is normal and the interlocutor does not complain about the loss of pieces of your speech, then the energy of both lines (UL and DL) is balanced and you can use a standard antenna tuned to the middle frequency between the receiving and transmitting frequencies. If the interlocutor disappears from time to time, it is necessary to "strengthen" the downward direction from the base station to your phone. It might be worth looking for a phone with better sensitivity. But if you are hard of hearing, you should strengthen the direction from your phone to the base station. Already at this stage, it is clear that when choosing the type of antenna and its parameters, it is desirable to take into account the operator's data and the conditions of reception.

In areas of poor reception, interference (interference) is often observed between channels with the same and adjacent frequencies. Unfortunately, the frequency resource allocated to GSM 900 operators in Russia is limited, which is why frequencies from different base stations with the same or neighboring signal strength values ​​are often "visible" in the poor reception area. Such frequencies create mutual interference that interferes with communication, and at certain signal levels, communication becomes completely impossible. If a strong signal from the base station is recorded on the phone screen, and the connection cannot be established, or it is possible, but speech disappears all the time, then you are faced with "strangers". It is not always possible to "force" the phone to select a different frequency, but a special feature of Nokia phones - Netmonitor - allows you to do this.

I ran into a similar problem in my dacha, which is separated from the big city by a rather open space. The phone received adjacent frequency channels with levels of 70 dB, 73 dB and 72 dB, but the communication quality left much to be desired. I was only saved by the forced selection of another frequency channel with a lower level - 80 dB. However, with a limited frequency resource, even frequency rescheduling of the network does not always help out. However, if your phone does not have a Netmonitor, you can use an external directional antenna with a good radiation pattern. All that remains is to make the right choice.

Antenna selection

As already mentioned, it is the external antennas that allow increasing the range and quality of communication. For telephones, external whip and log-periodic antennas, as well as wave-channel antennas, are mainly used. Let us repeat that in Western Europe there are no areas of hesitant reception. Therefore, directional antennas for GSM 900 terminals are practically not available. If the manufacturer offers a branded directional antenna GSM 900, it is usually designed to work with repeaters (repeaters) of operators.

In the CIS and Eastern Europe, directional antennas are handcrafted. In addition, there are small factories in the Czech Republic, Poland and the Baltics. A simple car magnetic antenna has a gain of 1 - 3 dB (1 - 2 cubes on the phone scale), a wave channel - 7 - 15 dB (depending on the number of elements, build quality and antenna settings), which is already 2 - 3 cubes on a scale , and a log-periodic antenna - 7 - 12 dB. The car antenna is a vertical rod of 3/4, 1/2 or 5/8 wavelength. Even a simple car antenna, raised higher, can correct the situation with an unreliable connection. The fact is that when talking on the phone, about 10 - 20% of the energy is absorbed by the user's body, therefore, lifting the whip antenna upwards, you reduce the influence of surrounding objects on it. I myself have observed how homemade, half-wave and vertical dipoles, raised by 5 m, solved the communication problem. Let us explain how such a dipole is made.

Rice. 1. Vertical dipole

We strip the white TV cable RG6U from one end. We get the center conductor and cable sheath. We solder a copper wire of any thickness about 8.2 cm long (for the 900 MHz band) to the central conductor and fasten it vertically upwards. We solder the second piece of wire of the same length to the braid and fasten it vertically downward (Fig. 1). We get something that looks like the letter "T" laid on its side. (Television uses horizontal polarization, while GSM uses vertical polarization, so just such a dipole is required.) Connect the other end of the cable through an adapter to the phone. Be careful not to short-circuit the braided center conductor or the phone may burn out. Well, in 5 minutes we built a primitive antenna that is not inferior in terms of parameters to Chinese automobile ones.

Let me give you a life story. Arriving last summer on vacation in Crimea, I found that there was no reliable coverage based on the operator's promised coverage. This meant that I would miss a very important call. A sure signal showed up on the roof of the cottage, but the prospect of sitting there for two weeks did not inspire me. In 5 minutes I found a piece of the right wire (instead of copper I used aluminum). It took another 10 minutes to find a 5-meter piece of television cable from the neighbors. The Nokia 7110 has a mechanical switch for the external antenna, so I just plugged the center conductor of the cable straight into the phone connector and connected the braid to the metal rim of the phone's external connector. He strengthened the antenna on the roof of the house and after 10 minutes, to the delight of the family and the envy of the neighbors, he spoke freely on the phone.

As they say, back to our rams. First, we'll use the automotive whip antenna ($ 5-10).

The main thing here is not to run into too bad quality. With Netmonitor, antenna testing is much easier. When the car antenna is connected to the phone, the signal level should increase by 1 to 3 dB (for example, from -60 dB to -57 dB). As a last resort, the signal should remain the same. If, when connecting the antenna, the signal decreases by 5 dB or more, it is better to abandon the purchase. I want to note that a good branded car antenna costs $ 40 and more. However, even among the Asian 10-dollar products, there are sometimes quite good things.

Mounted on the roof of your "village house", a car antenna can solve your communication problem. If the gain of a car antenna is not enough, you can turn to other - for example, to a common directional antenna - wave channel. It looks like a regular TV antenna installed on the roof of a house.

The wave channel allows you to get a real gain of up to 7 - 15 dB with an optimal radiation pattern. But it has a drawback - narrowband. The difference between the receiving frequency and the transmitting frequency in GSM 900 is 45 MHz, and the entire operating range is 890 - 960 MHz (70 MHz bandwidth). It is difficult to achieve linear or close to linear characteristics in such a wide range. Therefore, it is desirable to make the wave channel depending on the frequency of the operator and the specific place and, depending on the situation, shift the resonance to the frequency of the upward or downward directions. For greater bandwidth, use only a loop vibrator, matching it with the cable - for example, with a balun; you should also limit yourself to a small number of elements, say, 3 - 12, since if there are more of them, it will be difficult to tune the antenna without equipment, in addition, the operating range of the antenna is narrowed.

I have dealt with many handcrafted wave channels. I state: in most antennas, the gain was less than 7 dB, some had a resonance at frequencies of 700 - 800 MHz instead of the GSM band and a standing wave ratio of more than 3 (during transmission, this can easily damage the output stage of the phone). Professionally made and tuned homemade antennas were rare.

Now the next step is log-periodic antennas (they can also be found on the radio market). Compared to the wave channel, they have a wider operating range. Therefore, such antennas are less critical to the accuracy of manufacturing and tuning. The real gain here reaches 10 - 14 dB.

Theoretically, if necessary, you can connect 2 wave channels, one tuned to the receive frequency, the other to the transmit frequency, but this is already too complex a system.

Cable and antenna adapters

In the 900 MHz range, the issue of cable selection becomes paramount. Domestic television coaxial cables can only be used to a limited extent (attenuation more than 30 dB per 100 m is too great). Of the available imported samples, RG6 is a double-braided coaxial cable. You can find it in any store. Attenuation is 20 - 24 dB per 100 m (checked experimentally). Commercial automotive whip antennas typically include RG59 cable with 28dB attenuation at 100m. A 12dB UCA antenna and 10m RG6U cable give a total gain of 9.6dB and at 20m, 7dB.

Most phones have an external antenna connector. In addition, for each type of phone there is a so-called antenna adapter (about $ 5), it connects to the indicated connector and is a short piece of cable, on one side of which there is a specific high-frequency telephone connector, and on the other - a standard RF connector. Typically, the attenuation in the antenna adapter does not exceed 1 dB. When buying an antenna adapter, make sure it is functional. When the adapter is plugged into the phone, the antenna built into the phone is turned off and the output stage switches to the adapter. In other words, if you simply connect the adapter to the phone, the signal on the scale of the phone should drop slightly. Then you connect an external antenna to the adapter and the signal increases. If everything goes like this, then the adapter is working.

Setting up the antenna on the ground

So you bought an antenna and connected it to the cable and to your phone. We climbed to a high point and started tuning the antenna. Position the phone so that the screen is visible. As already mentioned, when setting up the antenna with Nokia devices, it is best to use the Netmonitor function. In most other phones, you can enter a special code and open the service menu, which allows you to see the reception level of 6 - 8 frequencies received by the phone in descending order, frequency numbers, distance to the base station, percentage of channel errors, etc. (For a description of many service menus, see . on: www.3ton.com/gsm.) If there is a Netmonitor, we will be guided by the signal level in decibels (remember that the signal is stronger when the level value in decibels is lower). If it is absent, we will tune according to the standard signal scale.

Since antennas of GSM 900 base stations are vertically polarized, the wave channel should be placed vertically. When aligning the antennas, pay attention to the fact that the receiving signal level displayed on the phone changes with a delay of up to several seconds, so the antenna should be turned slowly and discretely. If you know the direction to the nearest city, start there. Rotate the antenna slowly horizontally. If a signal is found, your task is to find the direction from which the signal comes with the maximum level. If there is no signal, slowly rotate the antenna horizontally until it appears. Remember that every meter of antenna height can be critical. If no signal is found, try to move a few meters to the side and search again. Maybe you're in luck.

It is undesirable to use a cable between the antenna and the telephone with a length of more than 30 m: in this case, almost all the signal is lost in the cable.

Finally, we give the dimensions of a homemade log-periodic antenna for the 850-950 MHz range (Fig. 2). Dimensions are taken from www.atnn.ru. The program for calculating the antenna-UW channel can again be found at: www.3ton.com/gsm.

Parameters: gain - 8.3 dB, wave impedance - 60 Ohm.

I hate to fish, because I feel sorry for the wasted time. But, nevertheless, I have been preparing for fishing all week. The task was to catch the mobile Internet and additional risks of the received signal level on the screen of a cell phone or smartphone, and it is necessary to catch it in the field without active amplifiers and batteries. This can be done using a passive repeater.

This, probably, already happened that in order to look at something on the Internet or call on a cell phone, you almost had to climb onto the roof or half hang out of the window, catching a risk on the screen of a cell phone or stuffing S MS to throw phone up, or raise together with the flag on the flagpole.

Try to make the simplest passive 3G signal repeater or cell phone first. Two simple directional wire antennas, a coaxial cable connecting them, that's the whole structure. With such a simple, power-free mobile device, you can communicate in a basement, in a metal hangar or garage, in a de-energized bomb shelter, or anywhere else the cellular signal cannot reach.

The size of the antennas themselves will correspond to the selected communication frequency: for a cell phone, frequencies of 900 MHz and 1.8 GHz, for mobile Internet, about 2 GHz. For the experiment, I made a 900 MHz antenna, but in practice it also turned out to be workable from 1.8 to 2 GHz. Subsequent measurements of the homemade antenna showed that the range of its excellent matching practically reached 2.080 GHz, otherwise I would not have received the 3G Internet signal.

If someone has already assembled a "simple antenna for receiving terrestrial digital television" from two wire rings, he will easily cope with the task. Everything is done in the same way.

The diameter of the mandrel (shot glass) is 4.3 cm. The frequency is 1.9 - 2.2 GHz.

Determine the wavelength in meters L m = 300/900 MHz = 0.33 m

Diameter of the coil (ring) of the wire D = L / 3.14 = 0.33 / 3.14 = 0.106 (m)

Distance between rings S = L / 4 = 0.33 / 4 = 0.08 (m)

Accordingly, with increasing frequency - the frames will decrease in size, the loss in the coaxial cable will increase. Antennas at other frequencies will also be calculated.

How it works. One directional antenna, removed from an absorbing reinforced concrete wall or raised above the metal roof of a country house, or simply raised above the ground, is oriented towards the base station. The second antenna, whether it is a basement or a country house, should be directed at or near a mobile phone or smartphone.

Since the antenna is directional, it has a gain, in a particular case equal to 5 dB. Some of this gain will be lost in the cable. In the cable RK 75 - 3. 7-35, 6 meters long at a frequency of 900 MHz, I lost, as it turned out later, 3 dB, which, taking into account the error, coincides with the technical characteristics of the feeder used. Antenna efficiency in free space with increasing height is better. It induces more field strength and improves line-of-sight with the base station, ensuring a stable connection, since houses and trees are no longer an obstacle to radio waves.

If you need to use multiple frequencies, you will need several repeaters with different ring diameters. Here, as in fishing, you need all kinds of bait, so I prepared the tackle like an avid fisherman, bending the wires like hooks to different diameters. Everything will depend on the conditions. Let's see what we can catch.

Test site.

It remains only to try. Here is the place of fishing, an old gazebo. A rod made of a miraculously preserved shortened antenna mast, which saved me when I flew from the roof, and therefore I definitely won't climb a tree, at my age the bones do not heal well. The pole was extended with plastic tubes, in which low-current wires are usually laid. Even a wooden glazing bead was used, because the antenna itself weighs little. Turning the fishing rod, I orient the rings towards the nearest town, temporarily turning into a fox hunter. Next to the antenna rings, which is below, I put my mobile phone.

With the help of a repeater, the mobile phone added three risks to the display, providing 100 percent communication with the nearest civilization (base station), located 6 kilometers beyond the forest. For those who like to chat on a cell phone for a long time outside the city, such a device is a must. As a rule, away from base stations, the phone gives off full power, which is unhealthy. The correct phone (meaning a small SAR value - sanitary standard), having a good connection with the base station, will give less power to the antenna, which means that the body is less exposed to the microwave field. But I already talked about this in the article.
"Protect yourself from cell phone exposure."

By the evening, there are more and more people who want to check their mobile phones and smartphones. The tablet came to life, slowly loading, showing individual pictures of television programs. The smartphone began to turn over the pages of the CLUB'S GRANDFATHER…. We were a few meters away from the repeater, but the Internet pages continue to turn over.

Everything is working.

Or maybe it's a joke, maybe 3G is already working everywhere?

I, offended, throw my fishing rod to the ground. From the disgruntled faces, you can see that everything is frozen, dashes and symbols flew from the displays.

I hate fishing, so much free time is wasted!

True, I have not yet seen a fisherman who has not returned to his old place to try a different bait. Only the diameter of the circle (900 MHz) has been tested, the diameter of the glasses is still ahead (2-2.2 GHz). Well, the bait on a spiral antenna will complete the catch. , I foresee in advance that a heavy construction will work out, but for a hospital it is what you need.

By the way, about polarization. In a hurry, or maybe out of absent-mindedness, I completely forgot about her, and when I was looking at the photographs, I remembered. Base mobile stations of cellular communication have antennas with vertical polarization, and therefore the tackle on the fishing rod had to be turned 90 degrees, so that the cut of the rings was not at the bottom, but on the side, which corresponded to a similar polarization. Nevertheless, the radio signal was caught even with horizontal polarization of the rings on the mast, despite the minimum loss of 6 dB due to mismatches, the experiment was a success. On the other hand, the forest has its own laws and the signal transmission with horizontal polarization is better in it.

P.S.

Two years have passed. This summer, in 2016, I was preparing for the arrival of my grandchildren on vacation from their parents or vice versa, and decided to conduct digital television in the gazebo, watch cartoons, and to catch my breath myself. So that the antenna would not be conspicuous, I wove it out of wires and called it invisible antenna. It turned out four rings, which, when receiving digital television, proved to be better than two ring structures. I wrote in detail about this design in the article "Invisible antenna - phased eight for terrestrial digital television".

I wove similar two antennas for a passive repeater of mobile communications for the 900 MHz range, so, just in case, suddenly someone needs the Internet. As of today, there is no Internet in our lowlands yet. The "H" icon appears, but it takes years to load. Having laid the double eight flat, he raised it to the level of the roof of the arbor, and it became invisible in the crown of a wild apple tree. Thanks to this design, the mobile phone added two to the two level risks. At this, it seemed, the experiment ended, but there was still a moment of triumph when the young parents urgently needed the Internet. The repeater did not disappoint, caught the Megafon operator, and quickly downloaded the necessary information. At that time, I felt like a wizard who opens a new spring with the help of a wire frame.

Smartphones and mobile devices have become part of our life, but even with almost 100% coverage, there are often places where these devices do not please their owners with the quality of received messages. Owners of mobile phones note a low signal level not only in areas remote from the city, but also in basements, in a metropolis with many high-rise buildings, in a car. You can use additional signal amplifiers or understand how they work and make them yourself.

To make a device that provides a high-quality message, you need to understand how cellular communication works, as well as have a diagram of the device and material from which you can assemble an external or internal additional antenna for a smartphone.

Mobile phone: basic parameters

An antenna for a mobile device is needed if the reception signal from the relay tower is of poor quality. This happens due to various circumstances. Consider, before looking for an additional antenna design, how cellular communication works. A modern mobile phone is a miniature radio station, its task is to receive and transmit messages on frequencies determined by the provider (mobile operator).

Experts, considering the ratio of signal transmission to its reception, determine the BS station (base station), and the mobile device MS (mobile device) that operate in the frequency range (935.2-959.8 MHz) is the base station → mobile phone, and in the ratio "reception - transmission" (MS) telephone - (BS) station in the range (890.2-914.8 MHz).

The first ratio parameters are called in a professional environment "Down Link" - this is the signal from the base station to the amplifier, and the second "Up Link" is the signal from mobile devices to an outdoor antenna.

The mobile operator always restricts the reception from the base station (BS) to a distance of up to 35 kilometers, since such a configuration of work allows the implementation of eight channels for conversation, which is accepted by the standard on the territory of the Russian Federation in the city. GSM operators work with fewer channels for conversation, a maximum of three, but the signal reception range is increased to 100 kilometers, this is a non-standard configuration and is used in coastal coverage areas.

Outdoor antenna selection

Not every 3g cell phone antenna can work for you. There are factors that affect the quality of signal reception, these are: the geographical location of the subscriber, what is the local terrain, what climatic conditions, the parameters of your smartphone and antenna.

The use of a car signal amplifier or a standard amplifier as an external antenna provides for their placement on the roof of a house or, respectively, on the roof of a car. It is recommended to direct it to receive a signal towards the nearest repeater, this can be achieved by rotating the antenna until the maximum signal reception value appears.

The wave signal receiving device in its design has: a traverse, a set of reflectors located perpendicular to the traverse. The dimensions of the reflectors are in relation to the receiving frequency, which is in direct proportion to the wavelength. This type of antenna for outdoor installation amplifies the signal well, but requires pointing accuracy to the base station (BS).

The parabolic view of the outdoor antenna has a design: a feed and a reflector. This type of signal amplifier can significantly enhance the reception, but special skills are required for installation, since with a poor-quality setting, the effect of the application will be "zero".

The flat remote antenna has a wide range of directivity and consists of an irradiator built into a reflector. To use it, it is enough to select the approximate direction to the side (BS), but the signal gain in this design is estimated as an average value.

The whip version of the external antenna is a rod that serves as a feed and reflector. In this design, the antenna has a circular directivity, in other words, it does not need to be directed in any direction.

Important! Experts do not recommend installing this type of antennas when screening structures do not interfere with the smartphone and the base. Recommended for installation in places where significant signal amplification from the base is not required.

Connecting your smartphone to an external antenna

The cellular antenna is connected to the mobile phone using a coaxial cable (RG6) high-frequency connector, since all smartphones operate at these frequencies. Amplification efficiency depends on the quality of the cable and connector. When the mobile device does not have an input for an external antenna, the wire from it can be connected to an open conversation device (speakerphone). The issue is solved even easier by wrapping the antenna wire around the mobile phone with three or four turns, which deprives the comfort of communication, but a good signal is achieved if necessary.

Note! In the event that there is a need to install stationary mobile communications, experts recommend buying a modem that is connected to an antenna, and can distribute WI-FI through a router to support cellular communications. A modem is not needed if the router has a GSM antenna connector.

How to make a diamond antenna yourself

There is not always the means to purchase a ready-made signal amplification device from a base station. How to make an antenna for a phone with your own hands - this question is asked by many cellular users in remote places of residence. Experts advise using the following tools and materials for these purposes:

• a knife for stripping the insulation from the cable;
• pliers;
• coaxial cable, RG6 recommended;
• soldering iron and solder;
• copper wire with a cross section of 2 millimeters and a length of 80 millimeters;
• phone adapter, you can use the Chinese model.

The order of work is as follows:

1. The coaxial cable must be stripped of insulation without damaging the inner core to connect it to the antenna, and connect the other end to the phone;
2. We bend the copper wire into a figure of eight along the rhombuses;
3. We solder a high-quality copper wire to the core of the coaxial cable in the "straight up" position. Solder the other end of the copper wire to the shielding braid of the cable in the "straight down" position;
4. We fasten copper wires on a plate with high-quality insulation of the connections;
5. We attach the resulting structure to the roof of the house, and use the adapter to connect the free end of the cable to the mobile device.

Important! Experts recommend strict adherence to the provisions of the copper wire, this will make it possible to receive a signal even when it is practically absent. A homemade diamond antenna is easy to implement, the cable connection must be done efficiently.

Elements for a cellular signal amplifier

The territory of the Russian Federation occupies a large area where there are places where the signal of the base station operator is not received without additional devices, the antenna for a mobile phone together with other devices collected in a single place allows you to forget about this problem.

Experts call such a device a cellular amplifier, which consists of the following elements:

• a two-way amplifier or repeater is an intermediate link between the telephone jack and the signal amplification complex;
• an internal and external antenna, the functional purpose of which is to pick up the signal from (BS) and spread it over a certain area;
• power elements, cable splitter;
• connectors;
• coaxial cable with a characteristic impedance of 50 ohms.

Experts divide all devices included in the signal amplification system into two groups: passive mode of operation and active mode. Active elements are a repeater and connectors that are connected to the power supply. Elements are considered passive: cable, antenna design, divider.

Important! In hard-to-reach places of signal reception, it is necessary to correctly calculate the antenna for a specific place. Experts consider this type of antenna to be the best option when the amplifier requires a minimum cable length, which makes signal losses per meter.

How does a repeater work

An antenna for a telephone through a repeater is an excellent solution for signal amplification, it is functionally responsible for signal amplification according to the (MS) → (BS) scheme and vice versa, when the signal is received according to the (BS) → (MS) scheme.

The antenna performs the function of receiving messages or transmitting them. You can assemble such an amplifier yourself when you have the skills to work with the instrument. The task of the external antenna is to process the incoming signal (receive it) or send it to the station, and the function of the internal antenna is to provide a stable signal coverage of the premises, in the subscriber's phone.

How to assemble a cellular amplifier

Providing stable communication in places where there are problems receiving a signal from a base station is a functional task of an amplifier that you can assemble yourself. It should be noted the clear advantages of this set of elements:

• stable reception in the geographic places of residence of the subscriber with the existing interruptions in receiving the signal from (BS);
• the amount of interference is reduced;
• messages are transmitted more clearly;
• low level of received radiation;
• the battery life of the phone increases with one charge.

The industrial version of this system costs "good" money, is a stationary complex, for this reason many mobile users make this complex on their own.

Assembly and elements of the signal amplification system

The complex for signal amplification begins with the manufacture of an external antenna. Once a simple diamond antenna is made and installed on the roof, it can be verified to work, these measures may be sufficient for your area.

Testing is carried out by a simple action, when the smartphone is brought to the amplifier, the signal reception indicator should show an increase in the number of divisions. You can make test calls to the operator (provider), determine the quality of communication. The whole assembly process fits into the algorithm:

• antenna manufacturing, outdoor and indoor;
• installation of a repeater;
• amplifier setting.

Important! It is not recommended to install the antenna near heating devices closer than one meter. Before work, you need to check all connected connectors for the quality of the connections. The repeater should not be exposed to cold temperatures.

If the connected system is not assembled correctly, it can itself be a source of additional interference. When there are power surges, you need to connect to the adapter through a voltage regulator.

Tuning the amplifier consists in obtaining the best gain of the amplified signal, preferably at least 15 dB. The repeater can be set to “manual mode” by rotating the potentiometer and changing the spatial position of the internal and external antennas. You can use "automatic mode" when the device is adjusted to full power output from the mobile device.

In places with poor signal reception from the provider's base station, you can always make a signal amplifier with your own hands, for a 3g smartphone. By their design, they are different, but functionally they have the same purpose - this is to amplify the signal. In a smartphone, the connector for connecting an external antenna is located under the cover of the mobile device. When the outdoor antenna is positioned correctly, towards the base station, it enhances the received messages in mobile phones.

Video

Recently, the coverage area of ​​GSM 900 networks in Russia has significantly increased, but the situation is far from ideal. If in European countries the problem of uncertain reception is practically absent, then the majority of domestic users often encounter it - in country houses, in summer cottages, etc. And how wonderful it would be to go fishing, hunting, to the countryside, without losing contact with the outside world !

The key to solving this problem is external directional or omnidirectional antennas. True, buying an antenna is not enough - you need to install and configure it correctly. Readers familiar with radio electronics will be able to independently manufacture and configure an antenna operating in the GSM standard. Today we will talk about the types of antennas and how to install and configure them.

reference
Quite simply, a mobile phone is a duplex radio station that communicates at different frequencies. There are 124 frequencies in the GSM 900 standard. The phone, like the base station, can operate on any frequency determined by the operator.

The base station (BS) transmits and the telephone (MS) receives on the frequencies 935.2 - 959.8 MHz. The mobile phone transmits and the base station receives at the frequencies 890.2 - 914.8 MHz. The channel from BS to MS is called Down Link, from MS to BS - Up Link. Most operators use the limitation of the range of the mobile phone from the base station - 35 km, which is due to the peculiarities of the standard. Let us explain that in a network of standard configuration, 8 time intervals (time slots) are formed in one frequency channel: one service, and seven - conversational. It is in this case that the maximum communication range on each channel is 35 km. However, GSM also provides for a non-standard cell configuration, in which the communication range is increased by 70 - 100 km (Extended Cell configuration). Unfortunately, with this configuration, the number of conversation channels is reduced to 2 - 3, which reduces the capacity of the network. It is not profitable for the operator to use this mode in the city and near the operator. This mode is sometimes used at seaside to create coastal coverage.

Thus, if you have a GSM 900 phone, do not try to establish a connection by moving more than 35 km from the nearest base station. The maximum communication range reached by me is 34 km.

Communication range
The following factors affect the radio communication range:

BS and MS location and terrain.

MS power and sensitivity.

BS power and sensitivity.

The will of the Lord God (experienced signalmen joke that this is the main thing).

Typically base stations have a power of 20 - 30 watts. Antennas are used either whip or directional. The sensitivity of base stations is -100 dB - 115 dB. The user, of course, cannot change or influence all these parameters. The phone's output power is 0.3 - 2 W, the sensitivity is 90 - 105 dB. The sensitivity of a phone is mainly determined by the technology used to create low noise input devices. If in areas of reliable reception the difference in sensitivity and power between the models is almost invisible, then in the area of ​​uncertain reception it can become critical. Often the handset shows the signal level from the base station 1 - 2 cubes (on a scale), but cannot establish a connection: there is not enough power. Although ETSI standardization regulates the standard output powers for each class of phones, the actual value may fluctuate slightly. SAGEM, Alcatel, Motorola handsets have good sensitivity. And in terms of power, all old phones, especially Motorola, pass by. All Phase 2 phones have roughly the same wattage.

As for the relief, on flat terrain and along the river, waves propagate better. The higher you are (within reason), the better the signal. The forest sometimes "dampens" the waves more than urban development.

Signal search
So, you've got out of town and want to provide yourself with a connection. Climb to the roof, attic, or the highest point near your home or location. If the phone picks up the network, but at the limit (or unstable), you have every chance to improve the situation using an external antenna. If the distance to the station is less than 30 km, and the network is not being caught, also try using an antenna. In the latter case, try to negotiate with the vendor to return the antenna if the experiment fails.

If the signal, albeit very weak, was still caught, dial any city number to check. If during a conversation the audibility is normal and the interlocutor does not complain about the loss of pieces of your speech, then the energy of both lines (UL and DL) is balanced and you can use a standard antenna tuned to the middle frequency between the receiving and transmitting frequencies. If the interlocutor disappears from time to time, it is necessary to "strengthen" the downward direction from the base station to your phone. It might be worth looking for a phone with better sensitivity. But if you are hard of hearing, you should strengthen the direction from your phone to the base station. Already at this stage, it is clear that when choosing the type of antenna and its parameters, it is desirable to take into account the operator's data and the conditions of reception.

In areas of poor reception, interference (interference) is often observed between channels with the same and adjacent frequencies. Unfortunately, the frequency resource allocated to GSM 900 operators in Russia is limited, which is why frequencies from different base stations with the same or neighboring signal strength values ​​are often "visible" in the poor reception area. Such frequencies create mutual interference that interferes with communication, and at certain signal levels, communication becomes completely impossible. If a strong signal from the base station is recorded on the phone screen, and the connection cannot be established, or it is possible, but speech disappears all the time, then you are faced with "strangers". It is not always possible to "force" the phone to select a different frequency, but a special feature of Nokia phones - Netmonitor - allows you to do this.

I ran into a similar problem in my dacha, which is separated from the big city by a rather open space. The phone received adjacent frequency channels with levels of 70 dB, 73 dB and 72 dB, but the communication quality left much to be desired. I was only saved by the forced selection of another frequency channel with a lower level - 80 dB. However, with a limited frequency resource, even frequency rescheduling of the network does not always help out. However, if your phone does not have a Netmonitor, you can use an external directional antenna with a good radiation pattern. All that remains is to make the right choice.

Antenna selection
As already mentioned, it is the external antennas that allow increasing the range and quality of communication. For telephones, external whip and log-periodic antennas, as well as wave-channel antennas, are mainly used. Let us repeat that in Western Europe there are no areas of hesitant reception. Therefore, directional antennas for GSM 900 terminals are practically not available. If the manufacturer offers a branded directional antenna GSM 900, it is usually designed to work with repeaters (repeaters) of operators.

In the CIS and Eastern Europe, directional antennas are handcrafted. In addition, there are small factories in the Czech Republic, Poland and the Baltics. A simple car magnetic antenna has a gain of 1 - 3 dB (1 - 2 cubes on the phone scale), a wave channel - 7 - 15 dB (depending on the number of elements, build quality and antenna settings), which is already 2 - 3 cubes on a scale , and a log-periodic antenna - 7 - 12 dB. The car antenna is a vertical rod of 3/4, 1/2 or 5/8 wavelength. Even a simple car antenna, raised higher, can correct the situation with an unreliable connection. The fact is that when talking on the phone, about 10 - 20% of the energy is absorbed by the user's body, therefore, lifting the whip antenna upwards, you reduce the influence of surrounding objects on it. I myself have observed how homemade, half-wave and vertical dipoles, raised by 5 m, solved the communication problem. Let us explain how such a dipole is made.

Rice. 1. Vertical dipole

We strip the white TV cable RG6U from one end. We get the center conductor and cable sheath. We solder a copper wire of any thickness about 8.2 cm long (for the 900 MHz band) to the central conductor and fasten it vertically upwards. We solder the second piece of wire of the same length to the braid and fasten it vertically downward (Fig. 1). We get something that looks like the letter "T" laid on its side. (Television uses horizontal polarization, while GSM uses vertical polarization, so just such a dipole is required.) Connect the other end of the cable through an adapter to the phone. Be careful not to short-circuit the braided center conductor or the phone may burn out. Well, in 5 minutes we built a primitive antenna that is not inferior in terms of parameters to Chinese automobile ones.

Let me give you a life story. Arriving last summer on vacation in Crimea, I found that there was no reliable coverage based on the operator's promised coverage. This meant that I would miss a very important call. A sure signal showed up on the roof of the cottage, but the prospect of sitting there for two weeks did not inspire me. In 5 minutes I found a piece of the right wire (instead of copper I used aluminum). It took another 10 minutes to find a 5-meter piece of television cable from the neighbors. The Nokia 7110 has a mechanical switch for the external antenna, so I just plugged the center conductor of the cable straight into the phone connector and connected the braid to the metal rim of the phone's external connector. He strengthened the antenna on the roof of the house and after 10 minutes, to the delight of the family and the envy of the neighbors, he spoke freely on the phone.

As they say, back to our rams. First, we'll use the automotive whip antenna ($ 5-10).

The main thing here is not to run into too bad quality. With Netmonitor, antenna testing is much easier. When the car antenna is connected to the phone, the signal level should increase by 1 to 3 dB (for example, from -60 dB to -57 dB). As a last resort, the signal should remain the same. If, when connecting the antenna, the signal decreases by 5 dB or more, it is better to abandon the purchase. I want to note that a good branded car antenna costs $ 40 and more. However, even among the Asian 10-dollar products, there are sometimes quite good things.

Mounted on the roof of your "village house", a car antenna can solve your communication problem. If the gain of a car antenna is not enough, you can turn to other - for example, to a common directional antenna - wave channel. It looks like a regular TV antenna installed on the roof of a house.

The wave channel allows you to get a real gain of up to 7 - 15 dB with an optimal radiation pattern. But it has a drawback - narrowband. The difference between the receiving frequency and the transmitting frequency in GSM 900 is 45 MHz, and the entire operating range is 890 - 960 MHz (70 MHz bandwidth). It is difficult to achieve linear or close to linear characteristics in such a wide range. Therefore, it is desirable to make the wave channel depending on the frequency of the operator and the specific place and, depending on the situation, shift the resonance to the frequency of the upward or downward directions. For greater bandwidth, use only a loop vibrator, matching it with the cable - for example, with a balun; you should also limit yourself to a small number of elements, say, 3 - 12, since if there are more of them, it will be difficult to tune the antenna without equipment, in addition, the operating range of the antenna is narrowed.

I have dealt with many handcrafted wave channels. I state: in most antennas, the gain was less than 7 dB, some had a resonance at frequencies of 700 - 800 MHz instead of the GSM band and a standing wave ratio of more than 3 (during transmission, this can easily damage the output stage of the phone). Professionally made and tuned homemade antennas were rare.

Now the next step is log-periodic antennas (they can also be found on the radio market). Compared to the wave channel, they have a wider operating range. Therefore, such antennas are less critical to the accuracy of manufacturing and tuning. The real gain here reaches 10 - 14 dB.

Theoretically, if necessary, you can connect 2 wave channels, one tuned to the receive frequency, the other to the transmit frequency, but this is already too complex a system.

Cable and antenna adapters
In the 900 MHz range, the issue of cable selection becomes paramount. Domestic television coaxial cables can only be used to a limited extent (attenuation more than 30 dB per 100 m is too great). Of the available imported samples, RG6 is a double-braided coaxial cable. You can find it in any store. Attenuation is 20 - 24 dB per 100 m (checked experimentally). Commercial automotive whip antennas typically include RG59 cable with 28dB attenuation at 100m. A 12dB UCA antenna and 10m RG6U cable give a total gain of 9.6dB and at 20m, 7dB.

Most phones have an external antenna connector. In addition, for each type of phone there is a so-called antenna adapter (about $ 5), it connects to the indicated connector and is a short piece of cable, on one side of which there is a specific high-frequency telephone connector, and on the other - a standard RF connector. Typically, the attenuation in the antenna adapter does not exceed 1 dB. When buying an antenna adapter, make sure it is functional. When the adapter is plugged into the phone, the antenna built into the phone is turned off and the output stage switches to the adapter. In other words, if you simply connect the adapter to the phone, the signal on the scale of the phone should drop slightly. Then you connect an external antenna to the adapter and the signal increases. If everything goes like this, then the adapter is working.

Setting up the antenna on the ground
So you bought an antenna and connected it to the cable and to your phone. We climbed to a high point and started tuning the antenna. Position the phone so that the screen is visible. As already mentioned, when setting up the antenna with Nokia devices, it is best to use the Netmonitor function. In most other phones, you can enter a special code and open the service menu, which allows you to see the reception level of 6 - 8 frequencies received by the phone in descending order, frequency numbers, distance to the base station, percentage of channel errors, etc. (For a description of many service menus, see . on: www.3ton.com/gsm.) If there is a Netmonitor, we will be guided by the signal level in decibels (remember that the signal is stronger when the level value in decibels is lower). If it is absent, we will tune according to the standard signal scale.

Since antennas of GSM 900 base stations are vertically polarized, the wave channel should be placed vertically. When aligning the antennas, pay attention to the fact that the receiving signal level displayed on the phone changes with a delay of up to several seconds, so the antenna should be turned slowly and discretely. If you know the direction to the nearest city, start there. Rotate the antenna slowly horizontally. If a signal is found, your task is to find the direction from which the signal comes with the maximum level. If there is no signal, slowly rotate the antenna horizontally until it appears. Remember that every meter of antenna height can be critical. If no signal is found, try to move a few meters to the side and search again. Maybe you're in luck.

It is undesirable to use a cable between the antenna and the telephone with a length of more than 30 m: in this case, almost all the signal is lost in the cable.

Finally, we give the dimensions of a homemade log-periodic antenna for the 850-950 MHz range (Fig. 2). Dimensions are taken from www.atnn.ru. The program for calculating the antenna-UW channel can again be found at: www.3ton.com/gsm.

Item number	Total length of vibrators (mm)	Distance from previous item (mm)	Distance from the end of the boom (mm)
	176
	141