Traveling wave RF antennas such as RG, RGD, BS, BS-2, ZBS-2 are bulky, expensive structures that occupy large areas of land. At large stationary radio centers, these antennas are used for critical communications and must recoup the costs of their manufacture. The stability and reliability of DKM radio communication lines with ionospheric propagation of radio waves is largely determined and depends on both the types of antennas used and their condition on this moment time. The general disadvantages of rhombic antennas and BS-type antennas include the presence of masts several tens of meters high with branched rigging. This deficiency is noted for the following reasons:
Limitations on the possibility of restoring the antenna by the center if at least one of its masts fails;
a) top view
b) side view
Rice. 7.42. Antenna BS-21/8.180/4,4.17
Limitations on the possibility of inspecting the antenna sheet, carrying out routine and preventive measures (lowering the sheet leads to loss of communications at a given operating azimuth);
Rising costs and increasing the time of construction and maintenance of antennas;
Limitations on the possibility of placing antennas on antenna fields.
Particular disadvantages of BS antennas include the presence of communication resistances (resistors), the number of which can reach several hundred. Resistors can burn out when exposed to lightning discharges. In this case, the antenna loses its original properties and its characteristics deteriorate.
A comparison of the main indicators of antennas of the OB, RG and BS-2 types (η is the efficiency of the antenna, and D is the efficiency of the antenna) allows us to draw several important conclusions. Let's compare the antennas and ZBS-2. From Fig. 7.43 it follows that the efficiency of a rhombic antenna is much greater than the efficiency of antennas of the OB and BS types, i.e. It is advisable to use it as a transmitting antenna. The efficiency of DKM range receiving antennas is not a determining indicator for them. Here, among the electrical parameters, the value of the directivity factor, associated with the direction of the main radiation of the antenna, comes to the fore.
Rice. 7.43. Towards a comparative assessment of antenna efficiency various types:
1 – OB, 2 - RGD; 3 - ZBS-2
From the analysis of Fig. 7.43 it follows that in terms of electrical performance, antennas of the OB-2 and BS-2 types are approximately equivalent, except for the lower efficiency of the BS-2 antenna in the long-wavelength region of the DKM range. Rhombic antennas, as receiving antennas, cannot compete with antennas of the OB-2 and BS-2 types in terms of range and directivity.
Let's compare typical antennas ZBS-2 and (see Table 7.21). In this case, we will limit ourselves to comparing only the main design parameters. The analysis shows that in terms of design indicators, antennas of the OB-2 type are significantly superior to antennas of the BS-2 type.
In Fig. Figure 7.44 shows the performance characteristics of the antennas mentioned above, as well as the OB-2 type antenna and several types of RGD antennas.
Rice. 7.44. Towards a comparative assessment of the efficiency of antennas of various types:
1 – , 2 – , 3, 4 and 5 – RGD antennas, 6 – ZBS-2
Table 7.21
Design characteristics of antennas 3BS-2 and OB-2
An antenna of type OB-2, in particular, with the help of insulators, can be installed on the rigging of an antenna of type BS-2 (Fig. 7.45) with very little effort and money. In this case, the antennas can operate independently of each other, being a mutual reserve. The antennas have linear mutually orthogonal polarizations, so the wires of the fabric and rigging of the BS antenna have almost no effect on the characteristics of the OB antenna. The antennas allow dual reception of radio signals using the polarization diversity method.
Antennas of the OB type have a relatively wide lobe of the radiation pattern, which reduces their noise immunity. The OB-E antenna does not have this drawback.
Figure 7.45. Layout of the OB-2 antenna on the rigging
antennas type BS-2
Antenna type OB-E
During development, the OB-E antenna was intended to be used at mainline radio communication receiving centers to replace antennas of the BS-2, 2 BS-2, 3 BS-2 types, which are the best available in terms of efficiency, but are bulky, expensive, unreliable in operation and labor-intensive to maintain. The OB-E antenna has a high efficiency/cost ratio C.
The OB-E antenna diagram is shown in Fig. 7.46. It is marked OB-E, where L– length of the antenna web; h– height of the antenna web suspension. In Fig. 7.46 is indicated: 1 – surface of the “ground”; 2, 8 – counterweight conductors; 3 – EMF source (radio transmitter, GSS); 5 – conductor with a traveling wave; 7 – resistor – load.
The antenna was marked OB-E (single-wire, traveling wave), where the letter E indicates the presence of another wave on the conductor, similar in structure to the wave E 0 in a round waveguide, if you look at the end of the conductor.
The OB-E antenna had a length L= 300 m; equivalent diameter of traveling wave conductor d eq = 280 mm; load resistor rating R n = 200 Ohm; suspension height h= 3 m. The operating frequency range of the OB-E antenna is Δ f= 3 ÷ 30 MHz.
Rice. 7.46. Antenna OB-E
Research has revealed fundamental differences in the operating principles of the OB and OB-E antennas. They suggest that a redistribution of radiation energy occurs in the near-wire space of the OB-E antenna, which led to the creation of a new, simple in design and very compact in diameter antenna for long-distance radio communications, which is a “horn antenna without visible walls.”
The results of RP calculations in the horizontal and vertical planes and experimental studies obtained using flybys at the same frequencies are shown in Fig. 7.47 and Fig. 7.48. Experimental points are shown with crosses.
From the analysis of the radiation patterns it follows that the OB-E antenna has high noise immunity.
Antenna complex OB-E
To receive signals arriving at different angles in the elevation plane, the OB-E antenna complex was created. It includes three OB-E antennas of different lengths L= 60; 120; 240 m, which are oriented to the terrain in one general azimuth.
Rice. 7.47. Calculated and experimental radiation patterns of the OB-E antenna in the horizontal plane
Rice. 7.48. Calculated and experimental radiation patterns of the OB-E antenna in the vertical plane
The complex is designed to receive radio waves in the range of 10 m £ λ £ 100 m, (3 ÷ 30 MHz) with ionospheric propagation on long-distance paths R> 1000 km. Recommendations for choosing receiving antennas are given in Table. 7.22. The parameters of the ionosphere are unstable in time and heterogeneous in space, therefore, at the point of reception of radio waves, instability of the angles q with respect to the horizon and fluctuations in field levels are observed.
Design characteristics of antennas 3bs-2 and ob-2
An antenna of type OB-2, in particular, with the help of insulators, can be installed on the rigging of an antenna of type BS-2 (Fig. 7.45) with very little effort and money. In this case, the antennas can operate independently of each other, being a mutual reserve. The antennas have linear mutually orthogonal polarizations, so the wires of the fabric and rigging of the BS antenna have almost no effect on the characteristics of the OB antenna. The antennas allow dual reception of radio signals using the polarization diversity method.
Antennas of the OB type have a relatively wide lobe of the radiation pattern, which reduces their noise immunity. The OB-E antenna does not have this drawback.
Figure 7.45. Layout of the OB-2 antenna on the rigging
antennas type BS-2
Antenna type OB-E
During development, the OB-E antenna was intended to be used at receiving radio centers for mainline radio communications to replace antennas of the BS-2, 2 BS-2, 3 BS-2 types, which are the best available in terms of efficiency, but are bulky, expensive, unreliable in operation and labor-intensive to maintain. The OB-E antenna has a high efficiency/cost ratio C.
The OB-E antenna diagram is shown in Fig. 7.46. It is marked OB-E, where L– length of the antenna web; h– height of the antenna web suspension. In Fig. 7.46 is indicated: 1 – surface of the “ground”; 2, 8 – counterweight conductors; 3–EMF source (radio transmitter, GSS); 5 – conductor with a traveling wave; 7 – resistor – load.
The antenna was marked OB-E (single-wire, traveling wave), where the letter E indicates the presence of another wave on the conductor, similar in structure to the wave E 0 in a round waveguide, if you look at the end of the conductor.
The OB-E antenna had a length L= 300 m; equivalent diameter of traveling wave conductor d eq = 280 mm; load resistor rating R n = 200 Ohm; suspension height h= 3 m. The operating frequency range of the OB-E antenna is Δ f= 3 ÷ 30 MHz.
Rice. 7.46. Antenna OB-E
Research has revealed fundamental differences in the operating principles of the OB and OB-E antennas. They suggest that a redistribution of radiation energy occurs in the near-wire space of the OB-E antenna, which led to the creation of a new, simple in design and very compact in diameter antenna for long-distance radio communications, which is a “horn antenna without visible walls.”
The results of RP calculations in the horizontal and vertical planes and experimental studies obtained using flybys at the same frequencies are shown in Fig. 7.47 and Fig. 7.48. Experimental points are shown with crosses.
Rice. 7.47. Calculated and experimental radiation patterns of the OB-E antenna in the horizontal plane
Rice. 7.48. Calculated and experimental radiation patterns of the OB-E antenna in the vertical plane
From the analysis of the radiation patterns it follows that the OB-E antenna has high noise immunity.
Antenna complex OB-E
To receive signals arriving at different angles in the elevation plane, the OB-E antenna complex was created. It includes three OB-E antennas of different lengths L= 60; 120; 240 m, which are oriented to the terrain in one general azimuth.
The complex is designed to receive radio waves in the range of 10 m λ 100 m, (3 ÷ 30 MHz) with ionospheric propagation on long-distance paths R > 1000 km. Recommendations for choosing receiving antennas are given in Table. 7.22. The parameters of the ionosphere are unstable in time and heterogeneous in space, therefore, at the point of reception of radio waves, instability of the angles pr relative to the horizon and fluctuations in field levels are observed.
Table 7.22
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Cellular communications have recently become so firmly established in our daily life that it is difficult to imagine modern society without it. Like many other great inventions, the mobile phone has greatly influenced our lives and many areas of it. It is difficult to say what the future would be like if it were not for this convenient type of communication. Probably the same as in the movie "Back to the Future 2", where there are flying cars, hoverboards, and much more, but no cellular communication!
But today, in a special report for, there will be a story not about the future, but about how modern cellular communications are structured and work.
In order to learn about the operation of modern cellular communications in 3G/4G format, I invited myself to visit a new federal operator Tele2 and spent the whole day with their engineers, who explained to me all the intricacies of data transfers through our mobile phones.
But first I’ll tell you a little about the history of cellular communications.
The principles of wireless communication were tested almost 70 years ago - the first public mobile radiotelephone appeared in 1946 in St. Louis, USA. In the Soviet Union, a prototype of a mobile radiotelephone was created in 1957, then scientists in other countries created similar devices with different characteristics, and only in the 70s of the last century were they determined in America modern principles the work of cellular communications, after which its development began.
Martin Cooper - inventor of the portable prototype cell phone Motorola DynaTAC weighs 1.15 kg and measures 22.5x12.5x3.75 cm
If in Western countries by the mid-90s of the last century, cellular communications were widespread and used by most of the population, then in Russia it just began to appear, and became available to everyone a little over 10 years ago.
Bulky, brick-shaped mobile phones that worked in the first and second generation formats have become history, giving way to smartphones with 3G and 4G, better voice communications and high Internet speeds.
Why is the connection called cellular? Because the territory in which communication is provided is divided into separate cells or cells, in the center of which base stations (BS) are located. In each “cell” the subscriber receives the same set of services within certain territorial boundaries. This means that moving from one cell to another, the subscriber does not feel territorial attachment and can freely use communication services.
It is very important that there is continuity of connection when moving. This is ensured thanks to the so-called handover, in which the connection established by the subscriber is, as it were, picked up by neighboring cells in a relay race, and the subscriber continues to talk or delve into social networks.
The entire network is divided into two subsystems: the base station subsystem and the switching subsystem. Schematically it looks like this:
In the middle of the "cell", as mentioned above, there is a base station, which usually serves three "cells". Radio signal from base station radiated through 3 sector antennas, each of which is aimed at its own “cell”. It happens that several antennas of one base station are directed at one “cell”. This is due to the fact that the cellular network operates in several bands (900 and 1800 MHz). In addition, a given base station may contain equipment from several generations of communications (2G and 3G).
But on Tele2 BS towers there is equipment only of the third and fourth generation- 3G/4G, since the company decided to abandon old formats in favor of new ones that help avoid interruptions voice communication and provide a more stable Internet. Regulars of social networks will support me in the fact that nowadays Internet speed is very important, 100-200 kb/s is no longer enough, as it was a couple of years ago.
The most common location for a BS is a tower or mast built specifically for it. Surely you could see red and white BS towers somewhere far from residential buildings (in a field, on a hill), or where there are no tall buildings nearby. Like this one, which is visible from my window.
However, in urban areas it is difficult to find a place to place a massive structure. Therefore, in large cities, base stations are located on buildings. Each station receives a signal from mobile phones at a distance of up to 35 km.
These are antennas, the BS equipment itself is located in the attic, or in a container on the roof, which is a pair of iron cabinets.
Some base stations are located in places you wouldn't even guess. Like, for example, on the roof of this parking lot.
The BS antenna consists of several sectors, each of which receives/sends a signal in its own direction. If the vertical antenna communicates with phones, then the round antenna connects the BS to the controller.
Depending on the characteristics, each sector can handle up to 72 calls simultaneously. A BS can consist of 6 sectors and serve up to 432 calls, but usually fewer transmitters and sectors are installed at stations. Cellular operators such as Tele2 prefer to install more BS to improve the quality of communication. As I was told, the most modern equipment is used here: Ericsson base stations, transport network - Alcatel Lucent.
From the base station subsystem, the signal is transmitted towards the switching subsystem, where a connection is established in the direction desired by the subscriber. The switching subsystem has a number of databases that store subscriber information. In addition, this subsystem is responsible for security. To put it simply, the switch is complete It has the same functions as the female operators who used to connect you with the subscriber with their hands, only now all this happens automatically.
The equipment for this base station is hidden in this iron cabinet.
In addition to conventional towers, there are also mobile versions of base stations located on trucks. They are very convenient to use during natural disasters or in crowded places (football stadiums, central squares) during holidays, concerts and various events. But, unfortunately, due to problems in legislation, they have not yet found wide application.
To ensure optimal radio signal coverage at ground level, base stations are designed in a special way, therefore, despite the range of 35 km. the signal does not extend to aircraft flight altitude. However, some airlines have already begun installing small base stations on their boards that provide cellular communications inside the aircraft. Such a BS is connected to a terrestrial cellular network using a satellite channel. The system is complemented by a control panel that allows the crew to turn the system on and off, as well as certain types of services, for example, turning off the voice on night flights.
I also looked into the Tele2 office to see how specialists monitor the quality of cellular communications. If a few years ago such a room would have been hung to the ceiling with monitors showing network data (load, network failures, etc.), then over time the need for so many monitors has disappeared.
Technologies have developed greatly over time, and such a small room with several specialists is enough to monitor the work of the entire network in Moscow.
Some views from the Tele2 office.
At a meeting of company employees, plans to capture the capital are discussed) From the beginning of construction until today, Tele2 has managed to cover all of Moscow with its network, and is gradually conquering the Moscow region, launching more than 100 base stations weekly. Since I now live in the region, it is very important to me. so that this network comes to my town as quickly as possible.
The company's plans for 2016 include providing high-speed communications in the metro at all stations; at the beginning of 2016, Tele2 communications are present at 11 stations: 3G/4G communications at the Borisovo, Delovoy Tsentr, Kotelniki, and Lermontovsky Prospekt metro stations. , “Troparevo”, “Shipilovskaya”, “Zyablikovo”, 3G: “Belorusskaya” (Ring), “Spartak”, “Pyatnitskoye Shosse”, “Zhulebino”.
As I said above, Tele2 abandoned the GSM format in favor of third and fourth generation standards - 3G/4G. This allows you to install 3G/4G base stations with a higher frequency (for example, inside the Moscow Ring Road, the BSs are located at a distance of about 500 meters from each other) to provide more stable communications and high speed mobile Internet, which was not the case in networks of previous formats.
From the company’s office, I, in the company of engineers Nikifor and Vladimir, go to one of the points where they need to measure the communication speed. Nikifor stands in front of one of the masts on which communication equipment is installed. If you look closely, you will notice a little further to the left another such mast, with equipment from other cellular operators.
Strange as it may seem, but mobile operators often allow their competitors to use their tower structures to place antennas (naturally on mutually beneficial terms). This is because building a tower or mast is an expensive proposition, and such an exchange can save a lot of money!
While we were measuring the communication speed, Nikifor was asked several times by passing grandmothers and uncles if he was a spy)) “Yes, we are jamming Radio Liberty!”
The equipment actually looks unusual; from its appearance one can assume anything.
The company’s specialists have a lot of work to do, considering that the company has more than 7 thousand in Moscow and the region. base stations: about 5 thousand of them. 3G and about 2 thousand. LTE base stations, and recently the number of base stations has increased by about a thousand.
In just three months, 55% of the total number of new operator base stations in the region were put on air in the Moscow region. Currently, the company provides high-quality coverage of the territory where more than 90% of the population of Moscow and the Moscow region lives.
By the way, in December, Tele2’s 3G network was recognized as the best in quality among all capital operators.
But I decided to personally check how good Tele2’s connection is, so I bought a SIM card in the nearest shopping center on Voykovskaya metro station, with the simplest tariff “Very Black” for 299 rubles (400 SMS/minutes and 4 GB). By the way, I had a similar Beeline tariff, which was 100 rubles more expensive.
I checked the speed without going far from the cash register. Reception - 6.13 Mbps, transmission - 2.57 Mbps. Considering that I'm standing in the center shopping center this is a good result, Tele2 communication penetrates well through the walls of a large shopping center.
At metro Tretyakovskaya. Signal reception - 5.82 Mbps, transmission - 3.22 Mbps.
And on metro station Krasnogvardeyskaya. Reception - 6.22 Mbps, transmission - 3.77 Mbps. I measured it at the exit of the subway. If you take into account that this is the outskirts of Moscow, it’s very decent. I think that the connection is quite acceptable, we can confidently say that it is stable, considering that Tele2 appeared in Moscow just a couple of months ago.
There is a stable Tele2 connection in the capital, which is good. I really hope that they will come to the region as soon as possible and I will be able to take full advantage of their connection.
Now you know how cellular communication works!
If you have a production or service that you want to tell our readers about, write to me - Aslan ( [email protected] ) and we will make the best report, which will be seen not only by readers of the community, but also by the website http://ikaketosdelano.ru
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An antenna of type OB-2, in particular, with the help of insulators, can be installed on the rigging of an antenna of type BS-2 (Fig. 7.45) with very little effort and money. In this case, the antennas can operate independently of each other, being a mutual reserve. The antennas have linear mutually orthogonal polarizations, so the wires of the fabric and rigging of the BS antenna have almost no effect on the characteristics of the OB antenna. The antennas allow dual reception of radio signals using the polarization diversity method.
Antennas of the OB type have a relatively wide lobe of the radiation pattern, which reduces their noise immunity. The OB-E antenna does not have this drawback.
Figure 7.45. Layout of the OB-2 antenna on the rigging
antennas type BS-2
Antenna type OB-E
During development, the OB-E antenna was intended to be used at mainline radio communication receiving centers to replace antennas of the BS-2, 2 BS-2, 3 BS-2 types, which are the best available in terms of efficiency, but are bulky, expensive, unreliable in operation and labor-intensive to maintain. The OB-E antenna has a high efficiency/cost ratio C.
The OB-E antenna diagram is shown in Fig. 7.46. It is marked OB-E, where L– length of the antenna web; h– height of the antenna web suspension. In Fig. 7.46 is indicated: 1 – surface of the “ground”; 2, 8 – counterweight conductors; 3 – EMF source (radio transmitter, GSS); 5 – conductor with a traveling wave; 7 – resistor – load.
The antenna was marked OB-E (single-wire, traveling wave), where the letter E indicates the presence of another wave on the conductor, similar in structure to the wave E 0 in a round waveguide, if you look at the end of the conductor.
The OB-E antenna had a length L= 300 m; equivalent diameter of traveling wave conductor d eq = 280 mm; load resistor rating R n = 200 Ohm; suspension height h= 3 m. The operating frequency range of the OB-E antenna is Δ f= 3 ÷ 30 MHz.
Rice. 7.46. Antenna OB-E
Research has revealed fundamental differences in the operating principles of the OB and OB-E antennas. They suggest that a redistribution of radiation energy occurs in the near-wire space of the OB-E antenna, which led to the creation of a new, simple in design and very compact in diameter antenna for long-distance radio communications, which is a “horn antenna without visible walls.”
1) Where is the best place to locate the base station?
The base station should be located at a high point so that the maximum number of clients can see its antennas. This could be the roof of a tall building, a tower, a factory chimney, etc.
2) What equipment is needed to create a base station (BS)?
The simplest base station(BS) consists of:
A. wireless router RES "RAPIRA"
b. RF cable with N connectors. An N-male connector is used to connect to the router. Depending on the type of antenna, the other end of the cable may use an N-male, N-female, or other connector.
V. Antennas - sector or omnidirectional
d. Drop cables type STP Cat.5
d. Power injector (included in the delivery set of RES "RAPIRA")
A high-performance BS can consist of 3 or 6 such sets, providing coverage of 360 degrees in azimuth. When using the dual version of the radio router wireless interfaces One router can be installed on 2 sector antennas, provided that the transmission frequencies are separated from each other by at least 100 MHz.
3) How many clients can be connected to one base station?
One base station can serve up to 128 clients per sector. It should be remembered that throughput base station is divided among all clients. Thus, the speed available to each client depends on the total number of clients, the load that each of them creates, the number and activity of computers in local networks hiding behind client routers. You can influence the allocation of base station resources using the tools QoS, shaping and prioritization to allocate each client the bandwidth it needs.
4) What do I need to connect the client’s local network to the BS?
You will need:
A. RES "RAPIRA" router configured in wireless client
b. HF cable with connectors. An N-male connector is used to connect to the router. Depending on the type of antenna, the other end of the cable may use an N-male, N-female, or other connector.
V. Directional antenna - parabolic or planar (panel)
d. Drop cable type STP Cat.5 (up to 100m)
d. Power injector (included in the RAPIRA RES delivery kit)
Depending on the results of the energy calculation, an antenna with the required gain is selected. The antenna is mounted so that there is direct visibility to the base station antenna.
The router is the gateway for the client's LAN computers. The client's LAN can be protected by FIREWALL built into the wireless router. You can also use the DHCP server function to automatically distribute IP addresses to computers and the NAT function to hide the entire client LAN behind one IP.
5) How much local networks client can be connected to wireless network through one wireless router RES "RAPIRA"?
RES "RAPIRA" has one interface in the “outdoor” version and 2 interfaces in the “indoor” version. According to the number of interfaces, you can connect 1 or 2 networks. RES "RAPIRA" also supports VLAN. By connecting a switch with VLAN 802.11Q support to the radio router, you can create up to 255 virtual interfaces and connect the corresponding number of local networks isolated from each other, providing routing between them and limiting access with FIREWALL access lists.
6) Can the available bandwidth for each client be limited?
Yes, the speed in the direction “to the client” can be centrally limited at the BS using the shaping function. In the “from the client” direction, the speed can be set on client radio routers.
7) What is the maximum service radius of the base station?
Maximum service radius, i.e. The distance from the BS to the most remote client depends in particular on the following factors:
A. transmitter power (depending on modulation) and receiver sensitivity, which in turn also depends on the selected speed (modulation).
b. Gain of the BS antenna and client antenna
V. losses in microwave cables and connectors (depending on their type and cable length)
d. the presence of barriers to wave propagation in the 1st Fresnel zone
e. interference from systems operating at the same or similar frequency
Typically, the service radius of a BS cell does not exceed 10-15 km. allows you to estimate in advance the maximum service radius when using various antennas and amplifiers.
8) Can I use amplifiers to increase the service radius or point-to-point channel length?
Yes, you can use an external amplifier. Modifications RES "RAPIRA" PA400 contain a built-in bidirectional amplifier. Using version PA400 allows you to increase the signal level for transmission by up to 10dB, sensitivity by 2-3dB and helps to increase the service radius by 2 - 4 times. Using version PA400 with built-in amplifier provides significant savings and additional operational benefits.
9) How to choose an antenna for a client station or point-to-point channel?
Remember the old and wise rule “antenna - best amplifier" Unlike an amplifier, an antenna does not introduce additional noise and does not amplify interference along with the useful signal at reception. A good directional antenna allows you to “tune out” directional interference by using a narrow beam. For example, a 0.9m diameter parabolic antenna provides a gain of 30dB and produces a beamwidth of about 3 degrees. At a distance of 5 kilometers, such an antenna produces a “spot” of radiation with a radius of only about 130 meters. In the 5-6 GHz range, the antenna sizes required to achieve the appropriate gain are smaller than for 2.3 - 2.5 GHz. Remember that parabolic antennas have best characteristics in terms of back and side lobes compared to planar antennas.
10) How to choose antennas for a base station?
Antennas forbase station It is better to use sector ones. The smaller the service angle (sector), the less interference such an antenna will “collect,” but the more routers and frequency channels such a BS will require to cover the required sector. Most common antennas with main lobe widths of 60, 90 and 120 degrees with gain from 15 to 13dB. Typically, in the vertical plane, the width of the lobe is 6-8 degrees, that is, the radiation is “pressed” to the ground and spreads along the horizon. The smaller the width of the main lobe antennas, the greater its amplification, due to the concentration of emitted energy. At choice and adjustment antennas should use the appropriate calculation to calculate the required antenna tilt according to the elevation angle. A vertical radiation angle that is too low can limit the connection of clients close to the base station, especially if the base station is located too high.
The use of antennas with a 360-degree omnidirectional pattern is not recommended when creating a BS with a large planned service radius and number of clients, especially in conditions of interference. In addition, the radiation plane is omnidirectional antennas is directed strictly horizontally and close subscribers located below the BS will experience communication difficulties.
12) Is “line of sight” necessary?
Yes, line of sight necessary in most cases. This means that there should be no physical obstacles (trees, buildings, etc.) on the imaginary straight line between the device antennas. You should also take into account the nature of wave propagation and make allowance for diffraction ().
13) What are Fresnel Zones?
Fresnel zones are the space around an imaginary line of sight through which a radio wave travels. At least 80% of this zone, in which the main radiation power is concentrated, must also be free of obstacles, otherwise the signal will be weakened. If you want to “shoot” into a gap between two houses, first the diameter of the 1st Fresnel zone. For example, for a 5.8 GHz channel with a length of 16 km, the Fresnel zone in the middle of the link is a circle with a radius of 14 m. The gap between houses must be at least 28 m. For 2.4 GHz the Fresnel zone radius will be already 34 m.
14) Can I “transparently” merge 2 LANs?
Yes, you can ensure transparent traffic flow through wireless routers"RAPIER", setting them up to work in bridge mode. In this case, Ethernet frames are filtered by a dynamic table of MAC addresses before being sent on the air. Read more about at a construction site equipment for working in this mode read the operating instructions.
15) How long does it take to install a simple wireless network?
Very little! A qualified team of 2 people usually requires no more than one day to install a point-to-point channel. Base station installation from 3 sectors and connecting 5 clients will require 2-3 days.
16) What length and type of RF cable should I use?
Shortest length. Remember that at frequencies 2.3 - 2.5 GHz, and even more so 5-6 GHz, the cable introduces very significant attenuation. RES "RAPIRA" specially designed for all-weather design to allow installation directly next to the antenna. In this case, you can use a flexible and easy-to-use cable brand 8D-FB (blue or green) or similar. If you want to place the antenna at a distance of 10 - 20 m from the router, you should use either a thick flexible cable with low attenuation, for example 10D-FB, or a rigid cable with appropriate connectors. We recommend using cables with solid foam dielectric. These cables are more stable and easier to handle. Cables with a dielectric in the form of an air gap, for example the common DX-10 brand (yellow cable), have a number of unpleasant disadvantages:
a. when installing connectors by soldering, as well as from heating during heat-shrinking of waterproofing, the thin internal dielectric melts and the cable loses its properties and begins to introduce enormous attenuation
b. During operation, due to changes in outside temperature and the associated periodic occurrence of air rarefaction, moisture accumulates in the dielectric cavity over time, causing the cable to become inoperable
c. cables change properties when bent because the central core is weakly fixed