Antennas for Routers: specifications, types

The type of communication for which the antenna is intended.

— Wi-Fi. A technology best known for wireless computer networks. The range of modern Wi-Fi equipment can be hundreds of metres; however, in fact, such distances are rarely dealt with, and such communication is still a communication with a relatively short range. Wi-Fi antennas can be used not only to ensure reliable reception / transmission of a signal, but also to optimize the coverage area — for example, to distribute the signal from a router standing in the corner (which would otherwise “shine” behind the wall, spending part of the power).

— 3G. Mobile communications of the third generation; it is the first generation to introduce comfortable Internet access speeds (comparable to land line speeds). In this case, the term "3G" can mean two different technologies — UMTS and CDMA. See "Frequency range" for more details.

— 4G (LTE). Mobile communications of the fourth generation. Formally, several technologies belong to this generation, but LTE is the most popular, and this is what is usually meant when talking about 4G. Not least, this is due to the fact that the LTE network can be implemented as an add-on over both GSM/UMTS and CDMA networks. The maximum data exchange rate in such networks is claimed at the level of 299.6 Mbps for reception and 75.4 Mbps for transmission; in f...act, the speed depends on the characteristics of the equipment and the distance to the base station. Note that the LTE standard has two varieties that are incompatible with each other — FDD (frequency division) and TDD (time division); however, each of them has its own part of the range table, and the consumer does not need to specify which particular variety is supported by his device — it is enough to make sure that the ranges match.

- 5G. The next, after 4G, edition of mobile communication standards. The 5G generation specifications claim a peak speed of 20 Gbps for receiving and 10 Gbps for sending data. Guaranteed, the user can count on high-speed information exchange rates of 100 Mbps for download and 50 Mbps for transmission. Also, a number of integrated solutions have been introduced in 5G networks aimed at improving the reliability and overall quality of communication. In particular, these are multi-element antenna arrays (Massive MIMO) and beamforming technologies (Beamforming) at base stations. The standard allows to reduce power consumption in comparison with predecessors.

Separately, it is worth touching on rumors about the dangers of 5G communications for health. According to modern scientific data, such a connection does not pose a danger to the human body, and the rumors mentioned are conspiracy theories that are not supported by any weighty arguments.

Note that, in addition to specialized ones, there are also “multi-purpose” antennas that allow the possibility of working with the two standards described above, or even with all at once.

The installation method for which the antenna is nominally designed.

— External. Models designed for outdoor use. The main difference between such antennas and internal ones is an increased degree of protection, which allows you to endure precipitation, temperature changes, dust and other "troubles" associated with working outdoors. Another feature is that the outdoor antenna can be quite large, which, in turn, has a positive effect on performance. It is this installation method that is used by the most powerful and “long-range” models (although, of course, the matter is not limited to them). Theoretically, an external antenna can also be installed indoors, but in fact this is rarely justified: firstly, because of the mentioned bulkiness, and secondly, because of the signal characteristics due to the presence of walls.

— Internal. Models designed for indoor use. They differ from external ones in smaller sizes, as well as in the absence of special weather protection (which is why it is highly undesirable to use such an antenna outdoors, at least). The specifications of internal antennas are also generally lower; however, they are quite sufficient for their main purpose. Also note that such devices have a more elegant design — in order to fit into the interior of the room.

Wi-Fi antenna compatibility (see "Intended use") with MIMO technology.

The name MIMO itself stands for "many inputs, many outputs". This quite accurately describes the general essence of this technology: it allows you to divide the transmitted data into several streams and receive these streams by several separate receivers. Thanks to this, at one time it was possible to create the Wi-Fi 802.11 bgn standard with a data transfer rate of up to 300 Mbps; the more recent 802.11ac standard (up to 6.77 Gbps) also uses MIMO. In general, this feature is becoming more and more popular not only in Wi-Fi equipment, but also in 3G / 4G devices (although it was originally developed specifically for Wi-Fi).

The specific requirements for external MIMO antennas are due to the fact that in a classic connection, each transceiver, in fact, requires its own separate antenna. Thus, devices supporting this technology can be two or more antennas in one housing (respectively, there can be 2 or more connectors). However, there are other variants of execution, where, due to the use of special technologies, MIMO is implemented differently.

The presence of a hermetic box for the modem in the design of the antenna. In this case, we are talking about mobile modems (3G and 4G), so hermetic boxes are found only in models that support mobile communications (see "Intended use"). Also note that all these antennas are exclusively external (see "Installation"); for indoor installation, the hermetic box is not required.

The hermetic box is a closed compartment that protects the modem installed inside from dust, moisture, sunlight and other adverse effects. This design allows you to mount the modem directly on the antenna, minimizing the length of the antenna cable and thus reducing the likelihood of interference. In addition, in some situations, such an installation is also optimal from the point of view of general convenience. However, there is rarely a real need for a hermetic box, so there are relatively few models with such a function.

— Omnidirectional. As the name implies, such an antenna works equally effectively in all directions; its radiation pattern has the form of a circle. Such models are intended mainly for situations where the signal strength is relatively high, but the signal itself can come from any direction (and it also needs to be broadcast in all directions). For example, this option is convenient for general-purpose Wi-Fi antennas, both on routers (installed approximately in the centre of the covered space) and on receivers like laptops (which can be in different positions relative to the router). And in 3G communications, omnidirectional antennas are useful mainly in dense urban areas, where the distance to base stations is small, but the signal is constantly reflected and changes direction. Note that all antennas of this type have a relatively short range.

— Directed. Antennas having a fairly narrow beam pattern — usually up to 60°, rarely up to 80° HBPW horizontally (see "HPBW / horizontal"). They are mainly used to organize communication on a point-to-point basis — for example, to connect a "home" 3G modem to the nearest base station or to connect a wireless access point to a Wi-Fi router in another building. A directional antenna needs to be pointed quite accurately, and such models are not suitable for use on the go. On the other hand, the narrowing of the beam has a positive effect on the gain and rang...e; it is these models that you should pay attention to if you need to receive a signal from a remote source or “break through” a thick concrete wall, which lacks the equipment’s own power.

— Sector. This type is a cross between the two varieties described above. The coverage angle of sector antennas is limited, but wider than directional models, ranging from 90° to 120° HBPW/H. Such devices are used mainly in Wi-Fi networks, when it is impossible to install a router in the centre of the covered space: they allow you to optimally distribute the signal from the edge of this space or even from the corner.

— Automotive. A specific category of antennas intended for installation in vehicles and having appropriate mounts — usually in the form of suction cups, for installation on the roof, hood or boot, etc. According to the radiation pattern, they are usually referred to as omnidirectional (see above) — otherwise it would be impossible to ensure efficient operation on a moving vehicle.

The type of polarization provided in the antenna.

Speaking very roughly and simply, a radio channel can be compared to a rope stretched from a transmitter to a receiver, and radio waves can be compared to the vibrations of this rope. Modern antennas for Wi-Fi and 3G are designed in such a way that these vibrations occur strictly in one plane — for example, up and down. Such waves are called polarized (more precisely, linearly polarized — other options are not relevant in this case). In the example above, the polarization is vertical, but there is also horizontal polarization, when the oscillations occur from side to side.

The general rule for choosing a Wi-Fi / 3G antenna for this parameter is as follows: the polarization must match the polarization of the antenna (antennas) with which you plan to communicate. Otherwise, communication efficiency will drop significantly — up to the complete impossibility of work. However, the main option today is vertical polarization — it is used by the vast majority of cellular and Wi-Fi equipment. "Purely horizontal" antennas are practically not produced, the ability to work in horizontal polarization is usually provided as an option; to do this, the antenna must be rotated by 90 ° around the horizontal axis relative to the standard position. Theoretically, this possibility is available for any antenna, but in fact it is worth turning only those models for which this possibility is...directly stated — they have the same horizontal and vertical HPBW (see below), and rotation does not affect the shape of the space covered.

Horizontal polarization can be useful when the air is loaded — it allows you to quite effectively separate the signal from other background (which is usually vertically polarized). However, this format of operation is rarely used, and, usually, for point-to-point connections, between two correspondingly rotated antennas.

There are a number of models that support the so-called dual polarization — when the signal is transmitted simultaneously in two polarization options. However, the need for such versatility is extremely rare, and it is expensive. Therefore, there are relatively few such antennas.

The effective angle spanned by the antenna in the horizontal plane.

Any antenna that is not omnidirectional radiates a signal in the form of a "beam", and unevenly: the power is highest in the middle of this beam and weakens as it moves towards the edges. The boundaries of HBPW are two opposite lines, on which the signal power is attenuated to half of the maximum. In other words, HBPW is a sector (in this case, horizontally) within which the signal from the antenna will not weaken by more than half and it will maintain acceptable performance.

Other things being equal, a more widely directional antenna will be more convenient in aiming at a target, and also more effective in difficult signal propagation conditions (for example, in dense buildings where it can come from different directions). A narrower focus, in turn, has a positive effect on the gain and, accordingly, the “range”.

The effective angle of coverage of the antenna in the vertical plane, technically — the angle within which the signal power will be at least 50% of the maximum.

For details about the meaning of this parameter, see "HPBW / hor." higher. Here we note that if the antenna is not tilted, then the middle of the covered sector (that is, the line where the signal is most powerful) runs horizontally. Therefore, if another device to be contacted is above or below the antenna, the latter will have to be tilted for maximum communication efficiency. However, absolutely accurate guidance may be required only when receiving a very weak signal on a narrowly directed antenna — in other cases, hitting the HPBW itself is quite enough.

The frequency ranges for which the antenna was originally designed. Communication technologies (see "Intended use") supported by the product directly depend on this parameter. At the same time, each type of communication includes several ranges, usually not compatible with each other. Therefore, when choosing a Wi-Fi or 3G antenna, it is worth considering not only the general purpose, but also the ranges within this purpose. Here are the most popular options:

— 2.4 GHz. The most popular band used by modern Wi-Fi equipment. It is standard for the Wi-Fi 802.11 b/g standard and one of the standard ones for the 802.11n standard. Supported by most appropriate antennas (see above).

— 5 GHz. The Wi-Fi band first introduced in the 802.11n standard (used in parallel with 2.4 GHz) and the only standard for 802.11ac, the most advanced Wi-Fi standard to date. Note that 5GHz-only equipment may not be compatible with older Wi-Fi 802.11 b/g devices; therefore, for guaranteed compatibility, it is recommended to combine a 5 GHz antenna with a 2.4 GHz one, or use a universal model that supports both bands (these are also available).

— CDMA 450. In general, the CDMA standard is known in the post-Soviet space for services such as "landline number on a mobile phone", as well as one of the most popular ways to "home" Internet connection via mobile networks (EV-DO technology is used). In this c...ase, we are talking about CDMA communication using the 450 MHz band. Another popular band is 800 MHz; there is no fundamental difference between them, so both options are often used by operators within the same country and even region. However, CDMA450 and CDMA800 are not compatible with each other. Thus, before buying an antenna, you should definitely clarify which standard the selected mobile operator uses.

— CDMA 800. A CDMA communication standard using the 800 MHz band. See "CDMA450" above for details.

— GSM 900. GSM is a mobile communication standard that was extremely popular around the world some time ago. Today it is considered completely obsolete (primarily due to low bandwidth), it is gradually being replaced by more advanced 3G UMTS and 4G LTE formats. However, both of these formats are extensions of GSM, and such networks remain compatible with the original GSM equipment. In addition, inexpensive GSM modules are still used in some special devices that do not require high communication speed (alarm systems, payment terminals, etc.). Thus, antennas for this communication standard are still being produced. Specifically, GSM 900 (the numbers indicate the operating frequency in MHz) is the earliest GSM communication range that appeared in Europe and Asia. It is inferior to GSM 1800 in terms of energy efficiency and network capacity, but it has a longer range and works better in dense urban areas, which is why it is still used today. And even newer phones remain compatible with GSM 900.

— GSM 1800. The GSM range, created as a development and improvement of the GSM 900 described above, with a doubled operating frequency (up to 1800 MHz — hence the name). Due to this, it was possible to halve the radiation power, as well as increase the network capacity (the number of devices that can work in it simultaneously). On the other hand, GSM 1800 requires a denser arrangement of base stations, and the signal loses a lot of power when passing through walls. Therefore, devices with support for this range are made backward compatible with GSM 900.

— UMTS 2100. Standard range of mobile communication 3 generations (3G) of the UMTS standard. Usually, this connection is what they mean when they talk about a smartphone or tablet with 3G. Such networks have been deployed on the basis of the existing GSM infrastructure, however, due to the nature of the signal, UMTS requires antennas specially designed for this range.

In addition to those described above, modern antennas (primarily "mobile") may provide other ranges — for example, LTE 800, 1800, 2600 and 5G 700 MHz, 5G 3300 – 3800 MHz in models for the corresponding communication standard. However, this is extremely rare and usually as an adjunct to one of the more common options.

— LTE 800. One of the three most popular bands used by 4th generation LTE mobile communications in Europe and the post-Soviet space (although less popular than those described below). Also known as band 20, according to the official band numbering. Refers to the FDD format (see "Destination — 4G (LTE)").

— LTE 1800. The fourth generation mobile communication band, also known as band 3. Was the most popular in the world in 2016, and it is likely that this situation will continue for quite some time. In part, this popularity is due to the coincidence in frequencies with GSM 1800 and the ease of deployment of LTE networks in this range.

— LTE 2600. Another common 4th generation communication range; the second most popular, after LTE 1800, for 2016. According to the band table, it is called band 7. It is considered quite promising due to the very small amount of extraneous interference in its frequency band; many telecom operators are switching or planning to switch to LTE 2600 even despite the rather high cost of such a solution.

- 5G 700 MHz. One of the lowest bands for 5G networks, 700MHz has good indoor penetration and is suitable for high-speed mobile network deployments in rural areas and along highways. 5G on this frequency provides wide coverage outside major cities using fewer base stations.

- 5G 3300 - 3800 MHz. The main frequency range for the deployment of fifth generation mobile communication networks. It provides stable coverage in dense urban areas and a large number of subscribers.

The impedance of an antenna is the resistance that occurs when an alternating current is applied to it. In modern Wi-Fi and 3G antennas, this parameter is standard and is 50 ohms. The cable that connects the antenna to the router or modem must have the same wave impedance — otherwise its efficiency will drop sharply (for example, a standard 75 Ohm television cable gives almost a two-fold power loss). However, many models have their own cable of quite sufficient length for use in the standard format, and usually you only have to pay attention to the characteristic impedance if you need to lengthen the “native” wire.

The highest power that it makes sense to bring to the antenna input. Theoretically, this parameter affects the compatibility with the transmitter, but the average user rarely needs this information. So, even in the most “delicate” short-range Wi-Fi antennas, this limitation is 1 W, while the power of consumer routers in many countries is legally limited to only 100 mW — a license is required for a more powerful transmitter. So paying attention to the maximum input power is usually for those who work with specialized equipment — for example, WISP access points.

The signal gain provided by the antenna.

In this case, we mean the gain relative to an perfect isotropic radiator — an antenna that uniformly radiates a radio signal in all directions in the form of spherical waves. Such amplification is carried out by narrowing the flow of radio waves, roughly speaking, by increasing their concentration in space (even omnidirectional antennas emit waves not in the form of a sphere, but in the form of a disk). In this case, the coefficient is measured by the maximum power, which is achieved in the centre of the radiation pattern. Note also that the decibel is used to denote this parameter (more precisely, dBi, decibel relative to the isotrope). This is a non-linear unit: for example, a difference of 3 dB corresponds to a difference of approximately 2 times, 10 dB — 10 times, 20 dB — 100 times, etc. There are tables and calculators that allow you to convert decibels to times.

All this means that the gain is a rather specific parameter, and when choosing its optimal value, consultation with special sources or a professional communications operator may be required. However, this is true primarily for specific situations — for example, installing a 3G antenna in a private house a few kilometers from the base station. The general rule is this: an increase in the gain has a positive effect on the communication range, however, it makes the antenna more susceptible to interference and, usuall...y, affects its dimensions and weight.

The type of connector, as well as its number, used to connect the antenna to a router, modem or other equipment.

— N-connector. A coaxial connector with a characteristic round shape, developed back in 1940, known primarily as a standard socket for connecting antennas to a TV. However, in Wi-Fi and 3G equipment, a 50 Ohm impedance connector is used — it has a thinner centre contact than the 75-ohm "television" one, despite the fact that otherwise both connectors are identical. This is not a problem if the antenna is connected to external network equipment with a “native” cable, however, when using third-party wires, care must be taken: when connecting different types of connectors, they may be damaged, despite the fact that the connectors themselves are not always marked. However, this is also not recommended for electrical reasons (see "Characteristic impedance").

— RP-TNC. A high-frequency connector that appeared somewhat later than the N-connector described above (in the late 1950s). Similar to it in size, it also has a coaxial design, but it is regularly made for a wave impedance of 50 Ohms, which made it convenient for Wi-Fi and 3G equipment. (There are also 75-ohm versions, but they are rare and have obvious differences from the standard ones).

— RP-SMA. A further development of coaxial high-frequency connectors created in the 1960s.... Like RP-TNC, it is standardly produced for a nominal resistance of 50 Ohms, but it is more miniature (almost 3 times smaller in diameter), which makes it well suited for compact routers and modems. At the same time, despite its small size, it provides a completely reliable and high-quality connection.

— MMCX. Coaxial antenna connector, which is small in size — the inner diameter of the socket is slightly more than 2.5 mm. Due to this, such connectors are widely used in various portable equipment. MMCX are designed for impedance of 50 ohms and frequency range of 0 – 6 GHz.

— TNC. The "original version" of the RP-TNC described above; appeared first, and later RP-TNC was created on its basis. Both interfaces are identical in size and general design of the connectors, but they have opposite polarity and a different distribution of contacts: in TNC, the “male” (male) contact is located on the plug, “mother” (female) is in the socket, in RP-TCN — vice versa. For a number of reasons, RP-TNC turned out to be more preferable for Wi-Fi and 3G equipment, and the original TNC was not widely used.

— FME. 50 ohm coaxial interface similar in size to RP-TNC but not identical. It supports frequencies up to 2.4 GHz, which is why it is found mainly in antennas for mobile communications and universal models.

— CRC9. Miniature coaxial interface, found mainly in 3G / LTE modems and antennas for them; however, it can also be installed in universal antennas. The connector diameter is only about 2 mm, which makes it easy to use in portable equipment. The cable under CRC9 often has an L-shaped plug to increase reliability.