Offset and direct focus satellite antennas: difference and tuning

A satellite dish has a number of advantages over
other antennas in terms of the quality of the transmitted sound and image. Satellite antennas are divided into offset and direct focus (toroidal antennas are rarely used in subscriber
satellite TV ), each of which has its own advantages and disadvantages. The article tells about the differences, installation, operation of these types of cymbals.
Offset and direct focus satellite antennas: difference and tuningTypes of satellite dishes [/ caption]

What is offset and direct focus satellite antennas

Reflective field antennas are divided into offset and direct focus antennas. Both belong to mirrored parabolic dishes, but have significant differences. The offset antenna is not as widely maintained as the second one. There is another name for direct focus antennas – axisymmetric, since their symmetry is built around one axis. Their mirror is a paraboloid of rotation, the shape is round, the structure contributes to the coincidence of the geometric axis with the electrical one. On the same axis there is a
converter , which is attached to the edges of the reflector by special construction.
Offset and direct focus satellite antennas: difference and tuningDirect focus dish [/ caption] The offset antenna is as if cut from a parabola. The paraboloid usually intersects with the cylinder. Their axes always run parallel to each other. The mirror of such an antenna has an elliptical shape, and the electric axis deviates at a certain angle from the geometric one.
Offset and direct focus satellite antennas: difference and tuningOffset antenna [/ caption] Both antennas have advantages and disadvantages. The direct focus antenna allows for more efficient use of the reflective area. The offset antenna has a slightly different structure. To obtain the effective area, you have to multiply the physical by the cosine of the angle between the two axes: electrical and geometric. But for a direct focus antenna, a significant part of the surface is obscured by the converter and its accompanying mount, which does not apply to another type of antenna. Therefore, direct focus antennas are usually quite large. In an axisymmetric antenna, which is raised at a certain positive angle, precipitation accumulates. Offset antennas are installed almost vertically or even tilted downward, and they do not accumulate precipitation. But, since the converter looks up, it must be made sealed,so that water does not seep inside. Another advantage of the offset antenna is that the entire center of gravity is shifted downward due to the bracket and converter, which give the bottom weight. Homemade direct focus antenna:
Offset and direct focus satellite antennas: difference and tuning

How to install and configure an offset antenna

Offset antennas have a shifted focus because the reflector is oval. These antennas are newer, they allow you to put a second and even a third converter, receiving more via satellite, depending on where they are. The
Offset and direct focus satellite antennas: difference and tuningso-called dragon is a satellite dish tuned to the three popular satellites Amos, Astra and Hotbird – this is possible only on an offset dish [/ caption] It is important that they the location was nearby. The “mirror” of this antenna focuses the signal on the converter. In it, the signal becomes lower in frequency by the frequency of the converter local oscillator. Passing through the
cable, the signal goes to the tuner, and the satellite receiver receives the signal passing through the satellite, processes it, decodes it, and transfers it to the TV in the form of a finished “picture”.
Offset and direct focus satellite antennas: difference and tuningSignal direction in offset and direct focus dishes [/ caption] If satellites are located close to each other, they are perceived by one offset antenna in the presence of two or three converters. Additional converters are attached using multifreeds. Sometimes it is possible to tune as many as four satellites. Consider installing three satellites. To
install the antenna , you need to determine where the satellites are in orbit. There are
programs and devices that determine the location, but you can navigate by the plates that are nearby.
Offset and direct focus satellite antennas: difference and tuningSetting the azimuth and elevation of the satellite dish [/ caption] Let’s imagine the orbit as a convex bridge. The first converter is installed on the satellite in the middle. The converters on the side are placed in accordance with the mirror image, that is, when the satellite is to the left and above, the converter is placed to the right and below the main one. It is important that there are no obstacles in the way in the form of trees, tall houses, etc.
Offset and direct focus satellite antennas: difference and tuningChoosing the right place for installing a satellite dish is the first task [/ caption] Installing a satellite dish: Offset and direct focus satellite antennas: difference and tuningChoosing the right place for installing a satellite dish is the first task [/ caption] Installing a satellite dish: The angle of inclination of the dish [/ caption]
Offset and direct focus satellite antennas: difference and tuningInstallation and adjustment of the offset antenna [/ caption] We put the wall mount vertically at an angle of 90 degrees from the roof. We attach firmly with bolts and dowels. The anchor bolts are driven into the holes and screwed tightly, the nuts are twisted, it is necessary to put a wall mount, at the end the nuts are tightened.
Offset and direct focus satellite antennas: difference and tuningOffset plate wall mount [/ caption]

Attention! It is better to install the entire structure of the house and then fix it on the wall mount.

A central converter is placed on the bracket and multifeeds are installed, to which the side converters are attached. First, we put a multifeed for the tallest satellite (if you stand facing the antenna, it is on the left side), fasteners are put on the arc, tightened, at the other end of this bar you need to put fasteners in the form of a ring, a metal tube is placed there, on which the converters are held. A converter is put on the multifeed. It is rotated about 100 degrees counterclockwise. One division is usually equal to five degrees. Threaded connection for six hours. Details on
how to set up a satellite dish .

Attention! When satellites are installed to the east of the south, the converter should be turned in the opposite direction.

We set the second and third converters in the same way, at a smaller number of degrees. We tighten what we have installed. But you need to do it without fanaticism, so as not to overdo it with the moment of effort. We prepare three pieces of wire, clean them and twist them onto F-connectors, clean the ends of the wires in protective rubber covers, put on these connectors. Setting up a satellite dish:

  1. At the beginning of the work, you need to install the main satellite. The wire from the converter is connected to input 1 of DiSEqC, from the output of the DiSEqC switch “Receiver” a cable is connected to the input of the receiver (tuner) and the equipment is tuned to the satellite that we need in a particular case. For this purpose, the satellite receiver is installed on the TV in the required parameters. The desired frequency is set manually.Offset and direct focus satellite antennas: difference and tuning
  2. When the signal “LEVEL + QUALITY” appears, you need to focus on “QUALITY”. The vertically standing antenna rotates to the right and left, in the absence of a signal, the tilt changes. When the signal is caught, we achieve the maximum. Then we start Scanning and see if we have chosen the right satellite.
  3. We tighten the fastening nuts.
  4. We connect the converter to the required input.
  5. We connect the DiSEqC switch.
  6. In the menu of the satellite receiver in the “Antenna Installation” mode, after choosing the converter settings, set DiSEqC in turn on the satellites.
  7. In the “Automatic tuning” mode, we scan all satellites. We need to check if they are captured. If everything is ok, you can watch TV.

Offset and direct focus satellite antennas: difference and tuning The main types of satellite dishes: https://youtu.be/46D9LqMqbzo

How to install and configure a direct focus antenna

The installation principle is similar, but the setup is slightly different. It is necessary to find
the elevation and azimuth . They can be calculated using an online calculator. Explore the menu, there is a section “Signal level”, which shows such important parameters as “Level” and “Quality”.
Offset and direct focus satellite antennas: difference and tuningWe collect the antenna. At first, the details look like this:
Offset and direct focus satellite antennas: difference and tuningAssembling the reflector. If you have washers, they must be installed. The stronger the structure, the better, you must take advantage of all these attributes.
Offset and direct focus satellite antennas: difference and tuningWe connect the halves with clamps and nuts.
Offset and direct focus satellite antennas: difference and tuningWe assemble the support structure, fasten the leg with a clamp.
Offset and direct focus satellite antennas: difference and tuningChoosing fasteners. Next, you need to set the plate on your leg. Then the whole structure is assembled, the legs of which resemble a spider. The inner tube should protrude about 2 meters. The scale for the legs, if any, is set somewhere at 38-40. Setting up a direct focus satellite dish for two satellites Yamal (90) + ABC (75): https://youtu.be/4vixVSd_-RY

Features of operation

Sometimes the antenna signal is too weak. Then you need to check if the plate mirrors are deformed so that it resembles a figure eight. It is important that if you look at the reflector parallel to the opening, the edges merge into a single ruler. If the receiver does not work well, you need to buy a new one. Sometimes it is necessary to purchase a converter with a lower noise figure. Sometimes you can buy another copy of the same batch. It is important that the feed of the converter is in accordance with the f / d parameter of the reflector.
Offset and direct focus satellite antennas: difference and tuningSpecification [/ caption] You can check the focal length when approaching and moving the converter from the reflector.

Interesting fact. Twice a year, at the autumn and spring equinox, the sun appears in line with the satellite and the receiving antenna. Then the solar radiation is in the converter along with the satellite signal. This degrades the signal quality. This can damage the equipment. Therefore, it is necessary to place a cardboard or polyethylene (opaque) screen in front of the irradiator in time.

How to choose a plate for your tasks

Each antenna is good in its own way. Offset is convenient to install along the wall. Snow and rain do not fall into them.
Offset and direct focus satellite antennas: difference and tuningA parabolic antenna is often associated with a satellite antenna [/ caption] But a direct focus antenna has an electromagnetic spot on the feed, free from all sorts of distortions, which affects the image in a positive way. The offset antenna is not affected by rainfall. It has a center of gravity fixed at the bottom. But the direct focus antenna is serviced on a larger scale. Therefore, it is up to the owners to decide which antenna to choose. To some extent, it is more convenient to use an offset dish, especially since it is preferred in private houses. But at the same time, both antennas are good in their own way. If desired, many manage to protect the direct focus antenna from precipitation. It is enough to protect the converter feed itself with a small visor made of a plastic bottle. Therefore, both versions of the cymbals are good in their own way, one must proceed from the individual situation.
Offset and direct focus satellite antennas: difference and tuning

Conclusion

So, satellite antennas, which are offset and direct focus, both perfectly pick up satellite signals, this is their similarity. They differ in the position and partly in the shape of the parabolloid, namely, the offset antenna is at right angles, and the straight-focus antenna is located horizontally. An offset antenna is better protected from all kinds of precipitation, and its center of gravity is better distributed, although an axisymmetric dish has an undistorted electromagnetic spot.

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