Television by satellite. Installation of satellite dishes
The satellites surround to us and they do it with different intentions. Some to see how it moves the air masses, others for espionage, others for GPS, others for telecommunications, etc. Of them those that interest to us are regarding the telecos.
We applied it. 1º Recordamos the magical word I PISS (not to confuse with CAGO, that thus does not leave the mnemonic rule to us)
2º Of I PISS I have the M of medium, the E of Earth and Or orbit
3. As I already have two last letters, coat LEO (L of Low) and the HEO (H of hight). Lack GEO with G of Geoestacioinaria
Therefore, we have the orbits:
1º I PISS = Medium Earth Orbit, usually they are placed the GPS satellites to about 20000 km We lowered and we fear
2º LEO, (Low Earth Orbit), to less than 5000 km of the Earth and where the satellites of movable telephony are placed (to about 700 km of the Earth) the television satellite use Earth plates always oriented to the same coordinates and, therefore, needs that the satellite that service gives them “not moves”. These are the satellites
3º GEO (Geostationary Earth Orbit). It is to a distance just as the Earth perimeter by the Equator, about 36000 km This are the belt of Clarke. To see development down a little but. We show an image where one imagines a satellite and a fixed point of the Earth. If it already is more far from those 36000, it is called
4º HEO de High Earth Orbit, and as soon as they have use. An important aspect of the types of satellite is what they take in giving a return to the Earth. GEO has the same period that the Earth (for that reason “they do not move”) but is more close, the period is smaller (go but fast) and if it is but far, the period is greater (they take but time of 24 hours in giving the return to the Earth). Because?
But, because the satellites do not fall?
Basically, the force of the gravity wants to fall it. The centrifugal force wants that it escapes. If we managed to equal the two, we will obtain a stable orbit. But info and interactive game in are WEB
The home (in the launching) is very important because, among other things, the speed of displacement is due to fix.
If the satellite moves very fast, it will leave the orbit towards the space.
If one moves very slow, the gravity will bring it direct towards the Earth.
When we have a satellite that tour of stationary form, we have an object that is turning at the same angular velocity that the Earth, that is to say, that if the Earth gives a return in a day, the satellite also.
We will see a little Physics. In the following drawing we have a mobile (satellite) giving returned with respect to the center (Earth). we have that revolving body has a mass m and as a result of it, the Earth attracts to him with an attractive force.
So that the satellite does not fall, the centrifugal force (force that of the center (centri) is wanted to escape) must be equal to the centrifugal force (that lies down to that it escapes)
We will see the first Fcf. In body mechanics revolving we have:
Fcf = - mw X (w x r)
Where m is the mass, w is the angular velocity and r the distance to the center of rotation.
It is a vector product with the salient resulting vector. The scalar value is:
Fcf = mw ² r
If the satellite is closely together, the attractive force is greater and therefore the centrifuge also.
If Fcf becomes major, but radius r become minor because we have approached the Earth, only has left that we must increase we the angular velocity and as a result of it, the period is smaller. The same reasoning if we moved away.
Now we will see the other force that wants to attract the satellite, so that the two are compensated. That force calculates by the gravitational force that is between both objects and has as value:
Where D is the distance of the center of the Earth to the satellite, M is the mass of the value Earth =5.98 1024 kg and G is a gravitational Constant of value G=6.67 10-112 Nm /kg2.
As the two forces must equal, we have:
As m (the mass of the satellite) we both have it in sides, they are possible to be cleared and in addition it passes D of the left to the right. The result is the following one
w is the angular velocity of the Earth (just as the one of the satellite) and calculates when dividing the angle that it must move the Earth between the time in seconds, this is: w2= 2*Π/24 hours =2*Π/(24*60*60 seconds) = 7.26 * 10 -5 radians/secondly.
Now it is called on to replace values:
. We obtain a value of D of 42297 km. That is the distance of the center of the Earth to the satellite. If we cleared the distance of the Earth radius, we have it distance of the surface to the satellite is:
42297 km - 6370 km = 35927 km
In a satellite that works, for example, in the Ku band, we have it ascent frequency is between 14 and 14.5 GHZ and the one of slope between 11.7 and 12.2 GHz.
Two frequencies are used so that the communications between earth and space do not have interferences
To use the high frequencies for ascent and losses for slope of data has an explanation.
In the equation of Friis , we have it received power is function of the used frequency, therefore, to major, for a same power of emission, it interests to use a lower frequency.
In the drawing of the satellite (to see above but), we have a component that is called transponder, that is the device that receives the signal to a frequency and it happens to another one of slope.
for each one of the channels (with bandwidth between 27 and 72 MHz, must at least have a transponder
Life utility: 15 years
In the Earth, we have the emission bases, calls telepuerto, that using satellite dishes (more directives). One of the most known is the one than it has Telefónica in Pozuelo de Alarcón) where you manage the channels (commercial and on watch) in the Astra satellites, Hispasat, etc)
1º Haz a table with the 4 types of orbital systems, specifying use, distance and period (how long it takes in completing a turn)
2º Investiga whichever satellites has in each orbit
3º In some films of espionage are some satellites of espionage where photographies and realtime images are obtained. It finds out who uses them, of what type are and because they do not have permanent vision of the objective.
4º a neighbor is seeing a party of TV received from the TDT. In our house, we received it by a Geostationary satellite (Astra). The celebration is annoying us. Because. To calculate the time that takes the signal in arriving at our plate. The frequency used for the Ku band differs to the ascent and the slope. The reason is the energy saving that supposes for the satellite. As the information raises “mounted” in a low frequency and in another one, transponder exists a denominated device. This device, receives the signal, the cleaning, it amplifies it and it transfers his frequency to lower it to the user.
Activity. The power of the signal that appears in each Earth point comes as much determined by factors technicians from the satellite as the own ones of the Earth. To the map that relates the received power of the satellite to the geographic area, footprint is denominated to him (treads standing up, that in “the sateliano” jargon denominates track of the satellite. As task sets out search the track of the satellite that uses Movistar and to make the following investigations being used the Web of satbeams.com and distel
a) What satellite uses
b) To obtain footprint of Europe and Spain
c) That power of dbW has in Spain and appreciable differences from an end to another one
d) To calculate the plate necessary to receive the signal well
We have a very good application of the company distel where we can verify and calculate the concepts that we are going to see. To look in this http://www.diesl.com/2014/01/13/como-elegir-el-diametro-adecuado-de-la-parabolica/ page and to make the calculations for the satellite, verifying the differences that exist to install a plate in A Coruña to put it in Malaga. In the used terminology, we have some important terms, eg:
Azimuth. Orientation angle of the satellite dish in the referred horizontal plane to the geographical north. For the Astra, we have an azimuth of about 150 degrees. To go to the Web satbeams.com/footprints and search where it is the satellite. To verify that S-value coherent.
Elevation: It is the inclination that we must give to the satellite dish with respect to the hotizontal plane to have the direction adapted to the satellite. (To see how this value modifies of happening from Cantabria to Malaga) and finally,
The angle of the polarization plane comes determined by the geographic location from the antenna and it adjusts turning the LNB, with respect to the vertical in the sense of the needles of the clock. Actually, usually one in the afternoon puts with the exit of the cable marking the 7.
Digital Video Broadcasting by Satellite is the system used for the transmission of waves by satellite. This system uses modulation QPSK (Quadrature Phase Shift Keying).
In the image superior we have the concept of modulation by phase that gives rise to a binary system (moduladora signal). Of down to above we have the first carrier wave, to a frequency of GHz. That signal does not take information and for that reason it is modulated with the moduladora signal (2º signal) giving rise to the modulated signal that she is the one that raises the satellite. In order to obtain the moduladora signal, it is come with a similar system to obtain the wished data.
Installation of satellite dishes
We are surrounded by satellites and, as we saw in the chapter Systems of radio communications, those that they position in the GEO orbit are those that interest us for the reception of signals of telecommunications (TV and radio mainly).
First that we are going to see it is the difference that exists between two “used plates” for these necessities.
Satellite dish is called because the form that it has is resembled a parabola, with the geometric property that all beam that affects perpendicularly to its surface, “bounces” to a focal point, unique, that is where we must take the sample from the signal and is that point where it will go located the LNB.
1º What satellite we chose?
In the majority of case we are going them to orient towards astra 19.2 This. In that point are several satellites of the Astra company.
3º Mounting an antenna
What antenna I buy. First of all, we must consider a) the track of the satellite and b) the climatology of the surroundings. For the satellite that occupies to us, with 60 centimeters of plate it is sufficient for all Spain and 90 0 120 cm for the Canary Islands.
a) We show footprint where the recommendation of the plate on the basis of the position (blue but intense is indicated, with signal but hard and, consequently, minor diameter of plate.
In the Canary Islands we have a weaker signal and the necessity to use a greater plate.
b) Environmental conditions. They order a work to us to put a parabolic one in a house. All good but to both year calls to us saying that is not seen. We review the installation and when raising the terrace we see that the antenna is fallen. The oxide has eaten the plate. We who we are in coastal zone, must have it in account.
The material of plates of the economic series usually is of iron plate with painting. Soon we can find galvanized plates, of aluminum or stainless steel. In the company diesl.es we have one, whose S-value 4 or 5 times superior to the normal one, but that it guarantees a good work to us. In this antenna it says to us
4º Elegimos the place of the house to mount the antenna.
The situation of the antenna within the house must reunite a series of requirements:
1º Tenemos to choose a place that is protected of gusts of wind. We will see when we mount a parabolic one, how one is affected by slight shifts of position. When long ago air, we can have images pixeladas as a result of the variation in the direction of the antenna. If there is terrace, to locate it low part partly where a wall serves as barrier to the air.
2º That are not obstacles against the same. Although the signal comes in an angle of 35 or but, we must have well-taken care of that does not exist objects that interfere in the signal. The rule is that:
5º necessary Tools and materials
Barranqueros swearwords and screws (to tighten with fixed key)
We show in these mentioned images the tool
As far as the materials and equipment, we needed:
1º Support for parabolic. There is a great diversity of manufacturers and models. Usually they become in galvanized iron.
2º LNB. Soon we will see it with but detail
3º Coaxial cable
4º satellite localizer. This equipment uses the feeding of the receiver to tell us if the antenna is oriented well. It has an entrance of the receiver and another one of the parabolic one.
In addition it counts on a small compass. When the antenna well is oriented sounds a whistle and in addition it shows the power to us of the received signal. In the image ours a 79%. In that case we must move as much slightly in horizontal as in vertical until obtaining the greater power. Once it arrives at the 100%, we must use the attenuator that incorporates, so that we happen to a percentage of 50%. We follow with the process before described until we approach the greater possible power.
6º Buscamos the satellite
6º Colocamos the support.
Before following with the manual, I leave an image you of two facilities. What could have been done in the first installation?
Once in the installation place, we must consider aspects of the wind, zone without obstacles, etc.
Chosen the point to put the support, we will put it so that the later movement of the antenna, does not hit with any element (wall or ground).
7º Turns in the satellite dish.
1º When we have the subject antenna to the support (without tightening to allow the movement in both felt) and using the compass, we make one first direction of azimuth, to the left and right, until we have something of signal.
2º Then, with the application of the mobile, we took the inclination of the antenna until which it indicates the APP to us.
There is a small measurer in the system of mooring of the antenna.
Once we got to have intensity of signal, we repeated with the azimuth movement.
The use of the localizer, since it has been indicated before, is going to allow to us to approach to us little by little the point of greater signal.
We will see a little exceeds what makes the LNB
The LNB (low-noise block converter) is component assets that include amplifiers, oscillating and converters of frequency, everything very integrated and to very low cost.
So that everything works is necessary that a tension is provided to him from the decoder. According to it is the tension, the LNB receives a polarization or another one of the signal of the satellite.
Because the frequencies of slope in the satellite (downlink, of the order of the 10 Ghz in the Ku band) would have the highest losses by coaxial cables, the use becomes necessary of this device, so that pass the signal of high frequency in a signal of smaller frequency, denominates Frecuencia Intermedia (FI).
To the band of FI of slope of the LNB is denominated it band “L” and understands the frequencies between 950 MHz and 2,150 MHz. We were with a problem. On the one hand, the bandwidth of the Ku band has 2,05 GHz (from the 10.7 to 12.75 GHz), that cannot go to other frequencies inferiors L since this band has a smaller bandwidth (1.2 GHz, that is the difference enters 950 2,150 MHZ).
Therefore, a subdivision of that one in two sub-bands is necessary, that are called Low band (from the 10.7 to 11.7 GHz) and another High band (included GHz enters the 11.7 12.75).
Due to the great losses of signal that has downlink, it is necessary to work with systems of low noise level, that usually oscillates between 0.1 dB and 1 dB. The signals that come to us from the satellites use 2 types of polarization simultaneously.
First it is HORIZONTAL the VERTICAL LINEAR polarization/and second, LEFT RIGHT CIRCULATING/and that it will be function of the type of antenna of has installed the satellite in downlink.
Generally and to avoid interferences with other signals, the frequencies used for a polarization are free in the crossed polarization and vice versa.
The great majority of the universal LNB of nowadays, uses linear polarization, with the capacity to select the polarization (following the entrance tension) and of the band (high or low) according to a 22 signal of superposed Kz the previous one (well-known as commutation tone). As a result of the previous thing, we have these combinations
13 VDC --> Vertical Polarization in Baja band
13 22 VDC + superposed Kh --> vertical Polarization in high band
18 VDC --> Horizontal Polarization in Baja band
18 22 VDC + superposed Kh --> Horizontal Polarization in high band
By our LNB we are going to obtain the different transponders from satellites according to the tension and frequency that we use to feed it.
The universal LNB have 2 local oscillating. One of them selects the low band and the other selects the high band.
Its function is, as we saw before, to lower the frequency so that deco can interpret it, within the rank that goes from the 950 Mz to the 2150 MHz.
When we see in some page of Internet the frequency of the transponder and its polarization, to obtain the Fi is simple. It is only necessary to reduce the frequency of the transponder and the frequency of the oscillator of the following form in band KU10700
a) For the low band (from the 10700 to the 11700) we must use the oscillator under (9750). To minimum value 10700, we cleared the value to him of oscillator 9750 and Mz gives to an intermediate frequency 950 loss us of. If we do equal with the high value of the band KU, we have 11700 - 9750 = 1950MHz
b) For the high band, that goes from the 11700 to the 12750, we come in the same way, obtaining the rank (11700 - 10600) and (12750 - 10600) = 1100 Mhz up to 2150 MHz
Example. For the CNBC we have a transponder 11597 V. We are in low band and to select that channel, deco must feed the LNB with 13 volts. In order to calculate the FI we reduced 11597 and 9750, giving rise to 1847 Mhz.
We go to the adjustment of the LNB.
This component can be turned on its support, and is necessary to take the suitable polarization. If we looked in the application of diels, it indicates to us that this adjustment is of about 27 negative degrees. This becomes referring to the south. We must turn the LNB until the exit of the cable is on the 7 of the clock. But precise it is possible to be done with the Transporter.
In the image the adjustment can be appreciated that becomes, taking into account that if the program says - 27º to us the turn of the LNB must look at the south and turning at the right.
And after all, what?
We are going to verify the result that we have in the measurer of the receiver. We must go to the section of adjustments and determine us to the section of Amount and quality of signal. We show two results indicating that in one something of signal with null quality is received and in another one the adjustment is acceptable.
Fine adjustment with the measurer of Field
Once we have everything as well as possible, and if we have a field measurer, we are going to come with the fine adjustment, with the idea to obtain the best possible installation.
The measurer is going to allow two important adjustments to us
1º Ajuste of the intensity of signal. This we obtained it visualizing the phantom with span suitable (on 200 Mhz) and observing how it varies db received. The fine adjustment of azimuth and elevation has the purpose of increasing this value
Practices with satellite dishes
We have already seen much theory and is necessary to take something of agility in the art to mount an antenna. We must consider that each manufacturer uses a system of different mooring. If we always bought the same, the installation will be to us very familiar.
Important. Of each one of the practices, we must document it with the suitable photographies and calculations to raise it Drive in a document pdf, that is called Parabolic.
Practice 1 In group of two, to mount an antenna on mast with all the elements (support, sweeps of the LNB, adjustment of LNB, coaxial cable and F connector. Once it mounts, dismounts so that the companion returns it to mount.
Practice of field. To lower the application to locate the satellite and search the coordinates (azimuth and inclination) of the satellite Astra 19,2.
Practice 3. We will make 3 clich3es with coaxial cable and F connectors. The length of the cable must be approximately 40 cm. Once finished will teach it to the professor and will make a photo of both clich3es to raise it the memory.
Practice 4. In group of 2, to mount an antenna on mast and to orient to Astra 19,2. Before leaving the classroom, to consider the tools that we needed. Once one is successful, to return to repeat it, being the companion the person in charge of the adjustment.
Practice 5. Using the field measurer, to make a fine adjustment of the parabolic one. To add in memory the photos of how it varies the phantom according to modifies the direction and the LNB (a pair of photos for each). PS. It is possible to be seen these passages in http://www.promax.es/esp/noticias/120/Instalacion-de-una-antena-parabolica-utilizando-un-TV-Explorer