How to choose a cellular signal booster (repeater)

Many of us face the problem of a weak or absent cellular signal. To solve this problem, there are special devices - GSM repeaters, amplifying the cellular signal and relaying it in the territory you need.

The principle of operation of the cellular signal amplifier is shown in the figure.

There are many repeaters and kits for self-installation on the market. The kits differ from each other in a variety of parameters unknown to the average customer. If they do not understand before buying, then there is a chance of a wrong choice and loss of money.

In this article I will explain in detail what points to pay attention to when choosing a cellular signal amplifier.

A typical kit for amplifying a cellular signal usually consists of the following basic elements:

• outdoor antenna
• indoor antenna
• amplifier (repeater)
• cable connectors

Outdoor antenna to enhance cellular signal

Outdoor antennas included in the package may vary, but, in general, there are two types - directional and non-directional.

In a city where there are a lot of base stations, it is usually not necessary to direct the antenna to the tower. Therefore, it is permissible to use a wide-angle panel-type antenna. Gain panel antenna is small, 5-7dB. But this is offset by ease of installation and configuration.

In places far from civilization where the signal level is small and has to be “pulled out” from afar, it is desirable to use an antenna with maximum gain. In terms of price / performance ratio, a “wave channel” antenna or a log-periodic antenna is best suited for this purpose.The gain of such antennas directly depends on the length and number of sections and is 8-14 dB. Some manufacturers include very short antennas (3-4 sections) in their sets, attributing to them frankly exaggerated characteristics that contradict the laws of physics.

In dense urban areas, directional antennas may also be useful. For example, if the BS of one of the operators is much further than the others, by adjusting the direction, it is possible to achieve uniform reception from everyone.

Conclusion:

An outdoor antenna should have a gain of at least 8 dB and, accordingly, directivity, which makes it possible to achieve high-quality reception in most cases. If the antenna has less gain, then the repeater will work poorly in conditions of a weak street signal. A low-power antenna is difficult to tune to a specific base station and to achieve uniform reception of all operators.

Indoor antenna to enhance cellular signal

• Whip antenna

Most often, the kits use small whip antennas with circular orientation. Such antennas are convenient for their small size and installation directly on the amplifier.The antenna propagates the signal around itself and allows coverage of the entire house.

• Panel antenna

Panel antennas, which are also used in sets, have some directionality. Panel antennas are larger than the whip and have greater gain. Connecting it directly to the repeater is not very convenient, it is usually installed on the wall and an additional cable is used to connect to the repeater. However, by placing such an antenna on the wall, you can direct it in the right direction, providing the necessary zone with communication.

• Antennas built into the repeater body

In the simplest sets, antennas are often found that are built into the repeater body. The gain of such antennas is minimal, and due to the lack of directivity, it is difficult to send it anywhere. To the repeater can not add a second antenna, if you need it. I would call this the most unfortunate decision.

Conclusion

Do not buy a repeater with built-in antenna inside.

Repeater

The main element of the gain system is the repeater. It amplifies the signal from the base station to the telephone and from the telephone to the base station. Let's look at the main characteristics of the repeater.

Material and size of the repeater body

Traditionally, amplifier housings are made of metal. It looks like this.

An example of a repeater in a metal case

In the process, the components of the repeater emit large amounts of heat and require cooling. In this case, the body serves as a passive radiator. In a plastic case, they produce, as a rule, low-power repeaters with a gain level not exceeding 50 dB. However, some manufacturers are cunning, indicating to reporters in plastic cases overestimated characteristics.

Conclusion:

In the plastic case only the most low-power amplifiers are made that can help only if the cellular signal on the street is very powerful and of good quality, which usually does not happen in places where this signal needs to be amplified.

Gain

This parameter indicates how much (in decibels) the amplifier can raise the input signal level. Repeater gain must be at least 60 dB. If it is smaller, then such a repeater has a very small sensitivity to the signal, and for its normal operation, we need a very powerful signal outside (full scale), which usually does not happen. Some kit manufacturers in the specifications indicate the total gain of the entire kit (repeater andexternal antenna), often attributing to its antenna unreal, fantastic characteristics. In reality, the amplification of a repeater in such a set may be small, which will lead to the fact that its coverage area will be small (1-2 meters), and subscribers will hear each other poorly.

Conclusion:

Before buying, find out the gain of the repeater itself, and not the kit as a whole. It must be at least 60 dB. If it is less, then do not expect a normal connection from the repeater.

Maximum power output

Maximum output power - the maximum signal level that a repeater can radiate to the inside of a room. To provide a small country house or apartment, the repeater output power should be at least 20 mW (13 dBm). In this case, the repeater should not exceed its passport capacity. If the signal on the street has increased, it should automatically adjust its settings. Chinese-made cheap repeaters do not have a maximum output power limit. As a result, being overloaded with a signal, the repeaters begin to distort the sound, the noise level rises, the sound quality is greatly distorted, the effect of the repeater becomes doubtful,and the device itself may soon fail. This also explains the fragility of Chinese repeaters.

Conclusion:

The repeater should have automatic control of maximum output power. It is absent from cheap Chinese repeaters, so they give unacceptable sound quality and are short-lived.

frequency range

In our country, 5 frequency bands are allocated for cellular networks:

• 800MHz / LTE
• 900 MHz / 2G, 3G
• 1800 MHz / 2G, LTE
• 2100 MHz / 3G
• 2600 MHz / LTE

The repeaters used in kits for self-installation, as a rule, reinforce one or two ranges.

Currently, this industry is developing rapidly. The frequency ranges of the broadcasting of different cellular operators in different places are very different from each other. Therefore, before buying a repeater, it is worthwhile to carefully understand at what frequencies the cellular operator you need works on. You can do this with a cell phone that has Android OS 7.0 or higher. Install one of the programs for the smartphone, for example: NetworkCellInfo, “Cell towers”, NetworkSignalGuru or other similar. In addition to the signal strength displayed in dB, these programs also display the frequency range.On smartphones with an OS version below Android 7.0, only the signal strength can be recognized.

Most often, people do not think about the frequencies, and choose a gain kit based solely on advertising, and kit sellers do not always seek to help in choosing.

So, a typical mistake is to buy a 900 MHz communication amplifier in a city where, as a rule, higher frequencies are always present. Phones refuse to switch from a weak 3G signal (2100 MHz) to an amplified 2G (900 MHz). As a result, the kit is completely useless.

The Megafon operator operates in the EGSM frequency band (925-935 MHz) throughout the country for voice communications, as well as 3G in the Moscow region. As a rule, Chinese repeaters do not enhance this range. If you buy a 900 MHz repeater and you need a “Megaphone”, you should carefully study the technical characteristics of the repeater before purchasing.

Conclusion

You need to buy a repeater in specialized stores or online stores, where before selling you will be asked questions about in what area and what operator you plan to use it. It would not be amiss to inquire about the possibility of returning or exchanging a repeater, if it didn’t fit in frequencies.Not all sellers exchange or return their equipment, not to mention foreign hypermarkets.

Amplifier quality

The quality of the amplifier is very important. Currently, the Russian market is overwhelmed with a stream of penny Chinese repeaters that have flooded the well-known foreign online stores. A poor-quality repeater, assembled on the principle of “bigger and cheaper”, besides the signal emits a large amount of intrinsic noise, therefore the quality of the signal amplified by such a repeater leaves much to be desired. A person who has bought such a repeater often faces the problem that the connection seems to have increased, but he still cannot talk normally - noises, wheezes, voice distortions are heard in the handset, individual words disappear or all words merge into a single indiscriminate flow. Moreover, since the repeater works in both directions, it also radiates the generated noise towards the base station, throughout the whole range of frequencies available to it. That worsens the quality of communication of all subscribers of this BS.

A correctly made repeater boosts the useful signal much better than noise, and the sound quality with it becomes noticeably better than without it.

In addition, the area of ​​coverage depends on the signal-to-noise ratio. The smaller the noise in the signal, the easier it is for the phone to recognize the useful signal and the longer the phone can be operated from.

Conclusion

A repeater made on the basis of a poor-quality amplifier will not solve your problem of improving communication. Due to the large amount of noise in the system, the voice will be strongly distorted, and you can hardly speak on the telephone. In addition, a less powerful but high-quality amplifier will provide a larger coverage area than a more powerful analog with a low-quality amplifier.

Manual or automatic gain control

Well, if the repeater is working normally. At the same time, it generates a minimum of noise and provides the most accessible quality of communication. However, such ideal conditions can be found far from everywhere. A strong incoming signal from one or several operators can overload the amplifier, and excess energy will break out of it in the form of noise. While operating in this mode, the repeater can not only quickly fail, but also create problems for the base station. In addition, the quality of communication will suffer - noise, interference, loss of voice you provided.The lack of manual and / or automatic gain control from the acquired repeater repeatedly reduces your chances of speaking normally with the subscriber.

Conclusion

The repeater should have automatic and / or manual gain control. Otherwise, it is likely that it will not help you, and you will have to buy another one - this time with adjustments.

Antenna Shielding Indication

In advanced models of repeaters they implement a very useful function - the antenna shielding indicator. The fact is that when installing a kit for amplification, it is very important to remove the external and internal antennas from each other well. Otherwise, the signal from the external antenna will be received by the internal one, amplified, and this process will occur many times, reminding the operation of the microphone next to the speaker. As a result of this “loopback”, the amplification system will not work normally. The screening indicator shows whether there is a “loopback” or not, which makes the installation of the gain system as simple and understandable for a non-expert.

Conclusion

Screening indication is a very convenient thing. Well, if the repeater is equipped with it.

Warranty period, warranty and after-sales service

A repeater is a complex and expensive device. It does not require maintenance, but there are cases of failure of some of its elements. If this happened during the warranty period, there is a legal opportunity to repair or replace the device for free. If the warranty period is over, then repair the faulty repeater can only be in a specialized service center of the manufacturer. Chinese repeaters, which are sold on the territory of Russia, do not have their own service center, and we can only guess how the warranty is carried out. Chances are that in the event of a Chinese repeater breakdown, you will only have to throw it out. Some Russian manufacturers of repeaters have their own specialized service centers, and also give up to 2 years warranty on their equipment.

Conclusion

It is better to buy repeaters of those manufacturers that have a service center in Russia, and also give a 2 year warranty.

Certification

According to the legislation of the Russian Federation, the operation of repeaters that do not have a certificate of the Ministry of Communications and Mass Media of the Russian Federation is prohibited.Violators are fined up to 40,000 rubles. The sample certificate of the Ministry of Communications is presented below. All other certificates that illegally hide behind unscrupulous manufacturers do not exempt buyers from administrative liability.

Conclusion

Operation of the repeater without a certificate of the Ministry of Communications of the Russian Federation is prohibited.

Cables and connectors

The kit for self-installation includes a cable assembly (cable with connectors mounted on it), connecting the external antenna with a repeater. Digital, broadband data transmission used in cellular networks imposes certain requirements on the type and quality of the cable used in the package. Around the world, shielded coaxial cable with a characteristic impedance of 50 Ohms is used for such systems.

Cable quality can be assessed visually. To avoid signal loss, the cable should be well shielded. High-quality shielding is impossible without the use of a dense metal screen, which gives the cable a certain rigidity. Cable thickness also affects gain quality. The thicker the cable, the larger the cross section of the central core, the lower the signal loss from the antenna to the repeater.

Cable assembly connectors may vary, but most commonly used are standard N-type high-frequency connectors or small SMA connectors.

And now let's imagine a situation - you have installed an external antenna on the roof or outside the window, and you need to get a cable inside the room with the connector already mounted on it. In this case, using SMA connectors looks more preferable, it allows you to pull the cable through small 8-10mm holes.

Conclusion

The amplification kit must include a 50 ohm cable (for example, labeled 5D-FB). It is better if the external antenna is connected to the repeater via the SMA connector, in which case you will not have to make a wide opening in the wall or in the window frame for the installation of the cable.

findings

Let's try to summarize the above and determine which set we should choose.

So, having determined the frequency and power of the desired signal, we proceed to the selection:

Conclusion

As you probably already understood, the repeater is a complex electronic device with many characteristics that are not immediately clear to the common buyer. Therefore, when buying a repeater, you should contact a specialized store or online store where you will find the right repeater. Before selling, the manager must find out what tasks and where you plan to solve with his help. Do not buy repeaters without any adjustments.This is not "frills", this is what you will use to ensure a quality connection. Do not pursue a profit of several thousand rubles, choose a reputable trusted Russian manufacturer who, if necessary, will provide you with technical support, warranty and post-warranty service. Enjoy the shopping!