Ⅰ. Fixation of antenna
Install the antenna together with the bracket on the antenna base. The direction of the antenna usually has a certain adjustment range, so there should be enough adjustment space on the left and right of the receiving direction. For the antenna with azimuth dial and pitch dial, the azimuth dial and 0 in true north direction should be used, and the 0 in pitch dial should be consistent with the horizontal plane. To determine the true north direction, the geomagnetic north pole is generally measured by a compass, and then corrected according to the local magnetic declination value, or it can be determined by Polaris or the sun.
Larger antennas are usually packaged and transported in pieces, so all parts should be reassembled during installation. After the antenna is assembled, special tools should be used to check the contour error, the relative position between the main surface and the auxiliary surface, and the relative position between the feed and the auxiliary surface to ensure that the error is within the allowable range. After calibration, tighten the bolts.
Whether the antenna feed is installed reasonably or not has a great influence on the antenna gain. For feedforward antenna, the phase center of the coincident feed coincides with the paraboloid focus; For the feed antenna, the feed should be fixed on the mounting hole of the top cone of the paraboloid, and the distance of the secondary reflection surface should be adjusted so that the paraboloid can focus on the phase center of the feed. The polarizer of the antenna is installed behind the feed. For linear polarization (horizontal polarization and vertical polarization), the narrow side of the rectangular waveguide at the feed outlet should be parallel to the polarization direction; For circularly polarized waves (such as circularly polarized waves), the vertical lines of the two narrow sides of the rectangular waveguide should intersect the plane of the screw or dielectric piece in the phase shifter at an angle of 45.
Ⅱ. Adjustment of antenna direction
Determine the due south direction. Firstly, the local magnetic declination (magnetic declination = reference annual value+annual variation value * annual difference) is calculated from the annual variation value and reference annual value (obtained by looking up the table), then the geomagnetic south pole direction is determined by a compass (or compass), and finally the calculated magnetic declination is used to correct the geomagnetic south pole, and the due south direction (due south = geomagnetic south pole+magnetic declination) is obtained. In addition, because the actual direction of the antenna pedestal is generally facing south, the antenna can be adjusted directly based on the direction of the antenna pedestal.
Conduct direction debugging. The debugging of antenna direction, specifically, is to adjust these two angles of antenna to these two values according to the elevation and azimuth calculated in advance, so as to aim at the satellite to be received and receive TV signals. This is the rough tune. Then fine-tune to make the received signal the best. Coarse adjustment is the foundation. How to judge that the elevation and azimuth of the antenna have been adjusted to the pre-calculated angle? There are many simple and effective methods according to the field situation and personal situation.
1, azimuth adjustment
After installing the antenna, turn the marked side of the tuner horizontally upward, then use the compass to find the direction of due south, and mark due south on the antenna post. At the same time, we need to know whether the azimuth of the satellite we are looking for is due south, east or west. Then find a tape measure to measure how many centimeters the circumference of the cylinder is, and then divide it by 360 degrees to get how many degrees per centimeter. Then divide the azimuth by the corresponding degree per centimeter, that is, how many centimeters you need to rotate. The antenna can be rotated to a nearby position.
2. Adjustment of elevation angle
After simple calculation and practice, it is concluded that the elevation angle should be: the calculated elevation angle MINUS 20 degrees (because the different errors of the antenna are between 19 degrees and 22 degrees). Then place a compass and fine-tune the elevation angle so that the pointer is the calculated difference (the error is between plus and minus 1 degree), which is the key to the success of antenna debugging.
Here is a brief introduction to a method-protractor and vertical line method:
With a large protractor and a little treatment, a convenient and practical simple elevation tester can be made, and the elevation can be read directly at any time without any calculation (as shown in Figure 3). Carefully drill a small hole in the center of the protractor, fix a thin wire here, and tie a small weight at the other end of the thin wire, and the elevation tester will be ready. When in use, as in the above method, the straight edge of the protractor leans vertically against the plane of the disc, and the end of the protractor engraved with 0 degrees faces downwards. At this point, you can read the elevation value while rotating the antenna elevation.
3. Adjustment of polarization angle
Before the antenna pointing adjustment, the preset direction of polarization angle P at the feed waveguide of the tuner should be roughly correct, and then fine-tune it after receiving the signal. Generally, the polarization angle can be roughly judged according to the longitude difference (longitude difference = the longitude of the satellite-the longitude of the receiving point). When the longitude difference is positive, it is also positive, and when it is negative, it is negative. The greater the absolute value of the longitude difference.
According to the data, we can know the parameters of polarization angle. Now align the horizontal line on the tuner with the 0 scale line on the antenna bracket. When the polarization angle is greater than zero, the tuner rotates clockwise. When the polarization angle is less than zero, the tuner rotates counterclockwise.
When receiving horizontally polarized signals, the narrow side of the feed waveguide port should be parallel to the ground, and the polarization angle p should be preset according to the difference between positive and negative longitudes and its absolute value, and then fine-tuned after receiving the signals. When receiving vertically polarized signals, the width of the feed waveguide should be parallel to the ground, and the polarization angle p should be preset according to the longitude difference between positive and negative and its absolute value. Ku band usually adopts feed integrated tuner. In order to make it easy to distinguish, some feed integrated tuners are marked with "up" on the end face, and the end face marked with "up" means "horizontal polarization" and rotated by 90 degrees means "vertical polarization".
When making the above adjustment, rotate the antenna slowly, and pay attention to the screen display of the TV monitor and the signal strength indicator bar of the satellite receiver, and adjust the adjustment position to the position with the strongest signal. Adjustment should be carried out item by item, and each adjustment point should be fixed. The adjustment sequence is azimuth-> elevation-> polarization angle. After all parameters are adjusted, finally fix the antenna.
Ⅲ. Installation and adjustment of tuner:
The installation of the tuner is relatively simple. Align the input waveguide port of the tuner with the output waveguide port of the feed or polarizer, add a sealing rubber pad in the middle and fix it with screws. The output end of the tuner is closely connected with the broadcasting of the intermediate frequency cable, and is coated with waterproof glue or rubber waterproof sleeve, and the effect is better by adding steel waterproof protective sleeve.
When receiving Digital satellite tv, use a digital dedicated tuner (some of them are marked with the word "digital" on the nameplate of the tuner). Due to the inevitable frequency offset and drift, in order to make the receiver work in the best state, it is necessary to fine-tune the intermediate frequency output by the tuner. Let it receive the analog signal on the satellite first, and reduce or increase the frequency (1? ) MHz makes the noise point minimum and the image best, and then returns to the digital station for reception. Avoid using inferior tuners, which ensures the reception quality of digital satellites.