How many antennas should a router have and what coverage does it receive?

Initially, when routers became popular, they had one antenna on board. Do you remember the retractable antenna on the first cell phones? No? And they were! Now you won’t surprise anyone with two or more antennas on a router. In principle, it may not be visible at all. It can be hidden, like on modern smartphones. In this article we will look at why some routers have so many antennas.

Why are antennas needed?

It is clear that any modem is a transceiver device. Initially, we connected to the Internet using cable. And at that time these devices were good. Now an antenna has appeared in the Router ↔ Computer chain. What type it is, hidden or open, doesn’t matter. The main thing is that without it it is impossible to transmit radio waves over distances.

Currently, all devices are equipped with an antenna:

• smartphones;
• Wi-Fi adapters;
• Wi-Fi routers.

Moreover, they may not be visually visible. And we are interested in the location of all antennas of the router.

There used to be phones with antennas sticking out. Now such models are no longer produced. The antenna itself remains, but it is not visible visually. Now they are inside the device.

This phenomenon fully applies to routers. If you have such a device in front of you, but the antenna is not visible, then remember, it is definitely present there. There are no routers, especially those with Wi-Fi functionality, without an antenna. Moreover, there may be several of them:

• one;
• pair;
• three;
• four or more.

As a rule, they are now external. This does not make the signal stronger. It's just that the antenna gain is higher. And the power directly depends on the transmitting device inside the router. This ensures the stability of the radio signal and increases the range. Now we have figured out that the main thing in a transmitting device is the gain. It is due to this that the Wi-Fi coverage area is expanded.

Now, let's move on to the question of why a router needs a lot of antennas.

Let's figure out how Wi-Fi works, why you don't need a powerful router, and what really affects the operation of the network

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Note : let me clarify right away - we are talking about the typical “home” use of Wi-Fi routers or access points, and not about specialized solutions that require long-distance communication, etc.

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There is strength - no need for intelligence?

Dark side of the force

So, let us initially have a certain standard router/access point with signal power parameters officially approved for our country, which operates “at full strength,” that is, at 100% transmitter power. As a reminder, this is 23 dBm / 200 mW in the 5 GHz band or 20 dBm / 100 mW in the 2.4 GHz band.

Note : The unit of wireless signal strength is measured in dBm or mW.

The signal emitted by the router/AP spreads around and reaches receiving devices, significantly weakening along the way. What approximately signal do we have on the client side (smartphone, tablet, laptop, etc.)? Well, for example, -50 dBm / 0.00001 mW or -67 dBm / 0.0000002 mW.

At the same time, the wireless client, which is usually a mobile device, has the task of not only connecting to the network, but also operating longer on battery power. Therefore, the client does not “throw” energy into the ether in vain. Clients' transmitter power is typically 11-17 dBm (12.5-50 mW). That is, this power is 8 to 2 times less than the signal power of the router, if we talk about devices in the 2.4 GHz range.

At the same time, wireless routers/APs always have a CCA Threshold - a signal audibility threshold, and if the signal level does not exceed this threshold, the router/AP considers it noise. Let's assume this threshold is 82 dBm. Thus, our conditional router with 5 dBi antennas will work with devices whose signal level at the point where the router is located is at least -87 dBm (-87 dBm signal + 5 dBi router antenna gain = -82 dBm).

Note : of course, this is a purely conditional example in which all parameters are conditionally typical and are given to understand the situation; your router may have antennas with a gain different from 5 dBi, and a different threshold, for example - for certain Ubiquiti equipment, generally stable communication is guaranteed at a signal level of up to -70 dBm; the threshold for 5GHz networks is lower than for 2.4 GHz even on the same equipment, etc., but these are nuances that we will not go into.

In general, a simple rule can be followed for the router and the client: all other things being equal, the signal loses 6 dB of power (i.e. 4 times) when the distance from the transmitter doubles.

However, as mentioned above, the signal strength of the router/AP is usually 2-8 times higher than on the clients. And with distance from the router/AP, a situation will inevitably arise when the client will hear the router’s signal well, but the router will hear the client’s weaker signal at the “edge” of its capabilities or not hear it at all (since the client’s signal level will drop below the CCA Threshold audibility threshold ). And a strange situation will arise when the Wi-Fi signal from the router on the client device seems to be caught, but there is no connection or it constantly “falls off”.

The reason is the asymmetry of the connection “strength”: for example, when a client with a power of 14 dBm hears a router/AP at -84 dBm (-84 dBm + 2 dBi client antenna gain = conditional hearing threshold -82 dBm), the signal reaches the router/AP from the client only at a level of -90 dBm, which is below the hearing threshold. Under these conditions, the wireless connection is guaranteed to be interrupted.

That is, in wireless communication channels, even with typical standard operating parameters of routers/APs, a significant communication problem arises caused by the asymmetry of the power of Wi-Fi emitters. And if you further increase the signal strength on one side (router/AP), the problem will only get worse. As you move with mobile clients, you will increasingly encounter a situation where a Wi-Fi router “loses” devices, precisely because it has a significantly stronger signal. The client will “hear” the router/AP, but the client’s router will not. This is why serious equipment manufacturers do not recommend using Wi-Fi routers and access points at maximum power. As proof, I provide a fragment of a Cisco presentation (the full presentation can be found here).

On the contrary, to eliminate asymmetry and obtain a stable connection, it is recommended to reduce the power of the Wi-Fi transmitter in the router/AP.

But if not signal strength, then what determines the speed and reliability of a Wi-Fi connection?

Connection speed, which doesn't mean anything.

Wi-Fi connection speed is determined by three parameters: modulation type, number of streams (depending on the number of antennas) and radio channel width.

But the “theoretical” connection speed based on the above parameters has little in common with the actual speed of the wireless network. What influences this speed?

The fact is that modulation in the network is not constant. The most progressive modulations today are 256 QAM and 1024 QAM (modulation determines how many bits are transmitted in one radio symbol). But! These dense modulations are very sensitive to noise. And they are achieved only with a high signal-to-noise ratio (SNR), when the client is close to the Wi-Fi router/AP. With distance from the router/AP, noise increases, SNR drops, modulation is simplified for connection reliability and, as a result, communication speed drops. Plus, interference adds its contribution to network problems.

Interference and noise

The cause of collisions due to interference in Wi-Fi networks are wireless devices operating on the same or close channel. These may well be neighbor's Wi-Fi devices, not yours, and you will not be able to influence their operation.

Note : in particular, it is therefore recommended to use non-overlapping channels for neighboring Wi-Fi routers; non-overlapping channels help to avoid interference (although, of course, they do not completely solve the problem - the problems grow with distance from the transmitters).

So, interference is interference caused by radio waves from neighboring Wi-Fi devices.

The source of noise in wireless networks are non-Wi-Fi devices that use the same radio frequency range as Wi-Fi equipment. These are various Bluetooth devices, 2.4 GHz and 5 GHz receivers, cordless phones, microwave ovens and other equipment.

Note : However, corrupted Wi-Fi packets and signals from devices outside the CCA Threshold are also considered noise. Signals from Wi-Fi devices operating remotely from the router on the same channel are not considered interference, since the signals from such devices cannot be demodulated.

How to reduce interference and noise in a Wi-Fi network? For a home user, I see only two options: switch to another channel and de-aggregate the channels. Since channel bundling itself already worsens the SNR: each additional 20 MHz channel takes away approximately 3dB from the SNR indicator.

Note : Reducing the channel width by 10 times increases the signal-to-noise ratio by the same 10 times. That's why the 802.11ax standard implements the idea of ​​dividing the channel into additional subcarriers. Narrowing the channel increases the signal-to-noise ratio, which made it possible to use progressive 1024 QAM encoding.

But the decisive influence on the performance of your network will not be the signal-to-noise ratio, not interference as such, not the strength of the wireless signal, and certainly not the number of wireless networks around, as many people mistakenly think. The performance of your wireless network will be largely determined by channel utilization. Well, unless you live in the taiga among bears, of course. There will be no one to utilize Wi-Fi channels except you.

Disposal problems

What is channel recycling? And why does it greatly affect the speed of the Wi-Fi network? Utilization is the share of airtime that is occupied by all devices operating on a given channel, and whose signals can be demodulated by our Wi-Fi router/AP, that is, the energy of which is higher than the CCA Threshold. In essence, the packets of our network are “squeezed” into the available narrow airwaves between the packets of other networks operating in the same radio range. Alas, our wireless network operates at maximum performance only when neighboring networks on the channel being used are not very active or idle (and best of all, if they are absent on it). That is why it is strongly recommended to go to the most “unoccupied” Wi-Fi radio channels. There are simply fewer network “utilizers” there.

Note : recycling is important because in Wi-Fi networks, access to the airwaves is implemented using the CSMA/CA protocol (carrier sense multiple access and collision detection), according to which wireless devices periodically “listen” to their frequency on the channel, and if it is busy, data transmission is delayed, and then after a while the device tries to listen to the frequency again.

Note that channel utilization does not in any way affect the wireless connection speed displayed in the system, but at the same time has a huge impact on the actual practical performance of the wireless network.

A living example: as soon as one of the wireless users downloads any large file (not to mention torrents), without setting reasonable restrictions on the download rate, the speed of all other users on the Wi-Fi channel used by such a user will drop significantly, namely due to channel disposal. Moreover, it does not matter whether users are connected to the same network, or to nearby networks using the same Wi-Fi channel. Moreover, the effect will negatively affect neighboring Wi-Fi channels too.

What level of channel utilization can be acceptable? Cisco believes that when the channel utilization is more than 80%, there is nothing left to “catch” in the network. No, the network, of course, will work even with such disposal. But we are no longer talking about working in anything close to real time.

Low channel utilization - excellent

Average channel utilization - acceptable

Note : it is not a fact that the channel on which there are the fewest Wi-Fi networks has the lowest channel utilization - it all depends on the operating scenarios of the networks. The channel(s) with the lowest utilization can only be determined empirically.

One of the effective means of reducing channel utilization (we are talking about means available to home users) is: switching to another channel, reducing the number of connected clients on the network, especially slow ones (it may be worth transferring them to a separate network), reducing the number of unconnected Wi-Fi Fi clients in the network coverage area, as well as reducing the range of the wireless router, that is, reducing the transmitter power (this will cut off the farthest and slowest clients that occupy the channel for a long time and “slow down” the network, as well as distant unconnected devices that regularly send management -frames, including those not your devices).

Note : To eliminate conflicts with neighboring Wi-Fi networks, a BSS Color (Base Service Station) identifier has now been introduced that tags each packet, allowing routers and clients to determine which packets are being transmitted from neighboring networks and simply ignore them. This reduces interference from neighboring wireless networks and speeds up data transfer, but this feature is only available in the latest 802.11ax standard.

Bottom line

As you can see, using a router with a high Wi-Fi signal strength does not mean that your network will work better, become more reliable or have a longer range. Quite the contrary. The more powerful the Wi-Fi router/AP and the larger the radius of its coverage, the more interference and noise such a device will catch, the greater the utilization of wireless channels and the lower the network performance. Moreover, such a gadget will create unnecessary interference for neighbors. Something like this.

Well, if you have anything to add to the above, please comment.

The post was rewarded.
This material was written by a site visitor and was rewarded.

How many antennas are needed?

Old systems were equipped with one antenna, and, at that time, this was enough for slow Internet speeds of one or two megabits per second.

But as time passed, the speeds increased. Old network equipment simply did not meet the new requirements.

For fast Internet, Wi-Fi must be much faster. To improve performance, it was decided to add a second antenna, because one could not cope with the reception and transmission of data (SISO) at the increased speed.

Two or more

Two antennas on the router ensured simultaneous operation of both reception and transmission using MIMO technology. Accordingly, the speeds also increased - up to 144 Mbit/s.

It must be said that modern smartphone models also have two antennas.

Let's add one more

If a 3x3 MIMO or 2x3 MIMO configuration is used for data transmission, then a third antenna may be needed, which also works for reception/transmission. This supports wireless networks at 216 Mbps. If the router can work using the TurboQAM or NitroQAM protocol, then the speed can increase significantly!

What if there are four

For an ordinary apartment with an Ethernet connection via twisted pair, there is no point in additional “antennae”. Theoretically, the speed can be 100 Mbps, but in reality it is lower.

And if you use a simple telephone line using the xDSL protocol, then the real speed is generally 20–30 Mbit/s. In this case, the optimal device would be a router with either two antennas or a built-in one.

It’s another matter if the Internet is distributed via fiber optic networks. They can provide speeds of 1 Gbps and higher. Here's an opportunity:

• live broadcasts of streaming video;
• chatting in Internet;
• Online Games;
• quality TV;
• telephone.

In this case, the use of routers with four “whiskers” will be justified. Especially if there are several Internet users in the house, and everyone has different preferences.

Biquad Wi-Fi Antennas

Strengthening the signal and transmitting it over long distances with a properly assembled antenna - up to 2 km in urban areas - in the most common Wi-Fi range of 2.4 GHz is done using various types of directional antennas. One of them is biquad, otherwise called by the name of its designer, Kharchenko. It consists of the following elements:

• a transceiver frame in the form of a double (or a multiple of two) diamond;
• a reflector made of aluminum, galvanized steel or copper plate;
• feeder line, the role of which is played by a coaxial cable with a characteristic impedance of 50 Ohms;
• connectors and adapters.

We position the router correctly

It may seem strange, but there are some users who consider it a worthy place to place something that is not conspicuous or has an outlet nearby. They don't think about how the router is positioned and how this will affect signal reception/transmission. If the device is installed by a specialist, then he already knows in advance how to properly place and install the equipment.

So where should the router's antennas be located and how should it stand? Obviously, the best position is in the center of the room.

This is partly true. If the apartment is one-room. What if there are two or three rooms?

If there is a dividing wall, then the place for the router is in the largest room on the wall that separates two adjacent rooms. But there are limitations. Household devices such as a refrigerator, microwave oven, stabilizers and other electrical appliances will interfere with the propagation of the radio signal. Therefore, it is better to stay away from all such devices.

It would also be a good idea to take into account where the Internet client is located in neighboring residential premises. The most advantageous installation point is at an equidistant distance from all network consumers. This is the best place to place your device.

Create it yourself

Assembling such a device is not difficult, but it will take some effort.

Biquadrat

To assemble such a device you need the following materials:

• wire;
• coaxial cable;
• wooden slats;
• pliers, hammer, knife.

Note! Before assembling the antenna, you need to carry out a qualitative calculation. There are specialized sites on the Internet that offer online calculators

Alternatively, you can use this site.

Assembly steps:

1. Calculate concepts such as polarization and wave frequency. Maintain linearity.
2. Make a vibrator and reflector from copper. All parts must be in the corners, one of which they touch.
3. Select one side according to the formula: wavelength, which must be divided by four.
4. Assemble the structure. It is recommended to make an oval shape without pulling the sides together.
5. Attach the antenna wire to the approach points on both sides. To block one direction of the diagram, you need to mount a fetal screen, which is also made of copper. It should be positioned at a distance of 0.175 mm from the working wavelength, and then placed on the wire braid.

Ultra-long

A fairly common name for such a catcher is “gun”. It is assembled from several steel disks with different diameters, which are secured with pins. Stages of assembly of such devices:

1. The first step is to cut copper disks of appropriate diameters.
2. Screw each of the disks onto special studs.
3. Connect the wires to the last two plates.
4. Connect the structure to the modem.

From an aluminum can

The simplest antenna, in which an ordinary can acts as an amplifier. To create it you need to cut off the lid. The result will be a barrel-shaped figure. Then you should strip the two ends of the wire: solder one to the bottom of the can, and connect the other to the antenna connector.

Powerful from sheet metal

In this case, the reflector is created from a metal sheet, which is recommended to be rounded. There are no special requirements for the vibrator; a biquadrat can be used. If there is no steel, it is recommended to use plywood or cardboard, which is wrapped in foil. The gain in this case will be slightly less.

A Wi-Fi antenna, even one you assemble yourself, will allow you to use your friends’ wireless network over long distances. There are several types of catchers. The choice of a specific one depends on the distance and terrain, as well as the user's tinkering abilities. In fact, everything is easy and simple, the main thing is to understand the assembly diagram and calculate the parameters.

Router antenna direction

For those who have a router with an internal antenna, this section is not relevant. But if there are two or more “antennae” on the router, then the question of how to correctly position the antennas of the Wi-Fi router will be very acute.

It is possible to adjust the distribution to the parameters of the apartment. But it is necessary to take into account such a parameter as the gain. The greater its value, the more the radius of wave propagation expands.

Now the most important thing is how the radio wave propagates. If this coefficient approaches unity, then the shape of the influence zone is closer to spherical. But modern devices have a coefficient greater than 1.0. Therefore, the shape of the coverage area is disk-shaped. In other words, the signal increases at the edges of the antennas, and decreases at the top or bottom of the “disk”.

What follows from this:

• In the first case, the coverage area of ​​the router can extend to several floors of the building.
• In the second, it is suitable for premises within a one-story house.

Now comes the fun part. Often modern models have several radio channels, for example, by the number of antennas. Therefore, if all the “antennae” are directed in different directions, then we will thereby change the reception/transmission zones along different planes. This will increase the range of the router.

It is also necessary to remember that antennas come in two types:

• Narrowly directed - the signal is collected into a beam and goes in the desired direction.
• Omnidirectional works in all directions.

A router with omnidirectional antennas, and this type is mainly used in modern devices, generally does not need to be aimed specifically somewhere.

Let's return to routers with built-in antennas. They are initially recommended to be mounted vertically on the wall. But since there may be more built-in antennas, for such models the vertical or horizontal position does not matter. Any directional transmission option will ensure stable operation of the device. You can even advise and work with different positions to see when the signal is best.

How should they be directed?

External antennas on the router, regardless of whether they are removable or not, are fixed movably. Their position can be changed. Many users have a question: how should the antennas be located on a Wi-Fi router, where should they be directed.

Note that there are two types of antennas: narrowly directional and omnidirectional. The first collect the signal into a beam and broadcast it in one specific direction. Omnidirectional broadcasts in all directions. Routers only use omnidirectional ones, so there is no need to aim them anywhere.

However, it is recommended to point the router's antennas upward. Installed in this position, they provide maximum coverage because the signal travels horizontally to the maximum possible distance in all directions.

If you place the antennas horizontally, the signal will propagate vertically, that is, up and down. Which is justified if you need to provide coverage on the upper and lower floors. In an ordinary apartment, it makes sense to place the antennas vertically with a slight slope towards the desired maximum coverage.

The antennas are made movable so that they can be installed as needed in any position of the router. After all, the router can either be installed on a flat surface - on a table or on the floor, or placed vertically on the wall.

As for routers with built-in antennas, some models are recommended to be placed vertically on the wall, since the antennas in them are horizontal . But most models have several of them inside the case, and they are located both horizontally and vertically, ensuring stable operation in any position. It is worth experimenting with different positions of the device to find out in which case the signal will be better.

Changing settings

There is another option to improve the quality of the radio pulse - change its settings. Let's consider why to do this.

Your signal may be clogged by transmissions from your neighbors’ router behind the wall, who also distributes Wi-Fi, but to their own apartment and, worst of all, on the same frequency. As a result, you will not receive enough Internet from this.

This problem can be solved by switching to another channel. Most routers do this. They can select the least loaded channel and go to it. To do this, you need to activate the “Auto” item in the list of Wi-Fi channels. Alas, not all devices have this function.

You can try increasing the radio signal power. However, this option is limited to the range from 0 to 100%. But if your router has the ability to increase the power level above the standard values, then this can save the situation.

The increase in power violates State Radio Frequency Commission standards. No one, of course, will control you, but still, keep this in mind.

Move the router away from metal surfaces

Remember that all metal surfaces reflect the Wi-Fi signal. Therefore, you should not place the router near large metal objects, such as metal shelving or safes.

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How to assemble a WiFi antenna

With our own hands we cut out a square plate with a side size of 110 mm from a textolite plate. We drill a hole strictly in the center for the copper tube. The diameter of the hole and tube must be the same. The plate must be drilled from the side of the copper coating. Along the edges of the hole, you need to tin the copper surface with a soldering iron. This will be a reflector. On a copper tube from one edge we grind one side along the diameter by 2-3 mm. We insert the tube into the reflector so that the ground part is on the side of the copper coating. The distance from the reflector to the end of the tube must be 16 mm.

We cut off 244 mm of wire and strip it of insulation. We make superficial cuts every 30.5 mm. After this, follow the marks and bend it at a right angle so that it looks like the number eight.

What is the range of Wi-Fi antennas

Often the distance is the most important parameter, for the sake of which the garden itself is fenced. Therefore, the question: over what distance can wifi be transmitted is of paramount importance. Several factors play into range. First of all, this is a line of sight zone. There should be no obstacles on the path between the receiver and transmitter. These distances can be increased by raising them to a certain height. The second point is the size and number of emitters. And the last thing is the directivity of the antenna. In the following, we will look at two types of antennas and their main features.

But it is worth understanding the following: the narrower the radiation pattern of a particular antenna, the higher its gain. But at a large distance and a narrow radiation pattern, any swing of the antenna by the wind will lead to the communication being uncertain. Therefore, they try to find a middle ground between the gain and the width of the radiation pattern. In reality, a good gain would be around 12 dB.