Selection of pot cover: The small pot cover is mainly used to receive high-power Ku-band programs. Because it is used as an offset feed antenna, its focal length is not in the center of the pot, so the curved surface of the pot surface is required to be relatively flat. If the surface is too deep, its efficiency must be very low. For example, the depth of the pan surface of the 0.6m offset feed antenna is only about 6.5cm, and the surface of the imported 0.6m antenna is smoother, and the depth of the pan surface is about 5.5-6cm. Usually the pot cover has 3-6 rings to reinforce the pot cover. The flatter the excessively curved surface of the ring, the better. If there are obvious steps, it is not suitable for use, because the signal will not be completely reflected to the feed plate of the tuner.
In addition, it should be noted that the pan surface should be smooth and bright, and the materials should be thick. As for the size of the pot surface, it is recommended to be between 28-35 cm. If the surface of the pot is large, its efficiency will definitely be better, but if it is large, it will lose the meaning of self-control. If the surface is wrong, its efficiency will be counterproductive. In the experiment, the efficiency of 1 aluminum pot cover with a diameter of 45cm is not as good as that of 35cm enamel pot cover, which is the reason for the low approximation of curved surface. This paper recommends three kinds of pot covers and homemade antennas. The former is convenient and useful to buy, while the latter is time-consuming and laborious, but the antenna efficiency is good.
About the focal length of LNB and antenna:
Usually, the formula for calculating the feed antenna is the square of the antenna radius divided by four times the depth from the antenna center to the disk surface. For example, the commonly used 1.5m antenna has a radius of 75cm and a disk depth of 25cm. Find the focal length A, the radius Y=75, the antenna depth H = 25, and substitute it into the formula A = 752 ÷ (4× 25) =. There is a quick way to find the focal length, that is, on the adjusted offset feed antenna, remove the pan surface, hold the pan cover in your hand, put it on the original antenna surface, move it up and down, back and forth, find the best focal length and elevation angle, and measure and record it. According to these data, a bracket can be made and the pot cover can be fixed on the bracket. This method avoids the pain of blind search and saves a lot of time.
The installation method uses the pot cover as an antenna, which is suitable for inversion. Because of the high elevation angle, less occupied space and easy fixation, the stability of the antenna is improved. The material selection and manufacture of the bracket can be considered according to different placement positions and convenient material selection. The following are several manufacturing methods and related dimensional data. ctvro.cn
ctvro.cn
1. Make antenna bracket ctvro.cn with shelf angle steel.
This material is characterized by convenient purchase. Angle steels are all strip holes and only need to be connected by screws, so it is very convenient to debug and easy to process. After the size is determined, the shop can cut it, providing the focal length and position of LNB, as well as the lid. Dimensions are for reference only, because different pot covers have different focal lengths, installation dimensions and elevation angles. The pan surface is 35cm in diameter and 30×30mm angle steel is selected. Each angle steel is connected with 6mm screws, and the lower plate is T-shaped. Make three three-point feet under the angle steel, with a height of 65438. Used between the front ends of angle steel, used to fix the pot cover and adjust the elevation angle. The hinge is fixed, and the rear end is fixed on the rear angle steel with M6 screw. The replacement of the upper and lower brackets is very simple, and it is best to combine them after cutting the size. This triangular base structure is strong enough and easy to move, and can be placed inside and outside the balcony. This antenna is in use. ctvro.cn
ctvro.cn
2. The scaffold ctvro.cn made of PVC pipe is selected.
ctvro.cn
Using this material as a scaffold is characterized by convenient material acquisition and simple processing. Floor-standing production, easy to move and debug, suitable for placing on the balcony. All PVC pipes are connected by PVC tees or elbows with special glue, and three pins of 10- 15mm can be installed on the three points of the T-shape, which makes it more stable when placed on the ground. For joints that need adjustment such as elevation angle and focal length, M6 expansion screw can be skillfully fixed at the elbow of the joint. The specific method is: remove the expansion pipe from the expansion screw, punch a 3.2mm through hole at the end of the screw, punch a 3.2mm cross hole on the PVC elbow, and tighten it with M3 long screw. The fly in the ointment of this antenna is that it takes up a lot of room or balcony space. ctvro.cn
ctvro.cn
3. Table lamp bracket ctvro.cn
ctvro.cn
Referring to the shape of desk lamp and microscope, the bracket of antenna in open-circuit TV room is selected, the original rod antenna is removed, and its base and elevation adjustment piece are used. There are several options for the finished product of this kind of bracket, as long as it is light and flexible in elevation adjustment and beautiful in appearance. This kind of bracket is a plastic shell, which is very light, and it is easy to fall over and unstable after being replaced by a satellite antenna. In order to increase the weight, an iron plate must be added to the bottom of the shell. The screws for adjusting the elevation angle on this bracket are mostly plastic and easy to slip, so they must be replaced with metal screws. In order to facilitate the adjustment of elevation positioning, a layer of rubber skin, such as tires, can be placed on both sides of the screw to increase its friction, so that when the elevation screw is 80% tight, when the elevation angle of the pan surface is changed by hand, it will not slide down. This style of bracket is very small and flexible, and it is suitable to be placed on a desk cabinet or on the windowsill of an indoor bay window, just like a handicraft. ctvro.cn
ctvro.cn
This kind of bracket is very simple to make, and there are few homemade ones. ctvro.cn
ctvro.cn
(1) ctvro.cn of antenna fixing bracket
Select a steel bar with a width of 20mm, a length of 500mm and a thickness of 1-2mm, and bend it at 180mm, with some radians on both sides to fix the antenna and tuner respectively. The support is made of local materials and connected with two steel bars. ctvro.cn
ctvro.cn
(2) Reinforce the side strips. When debugging the antenna, measure the distance between the pan surface and the tuner fixture. Use a 0.8- 10mm thick metal strip, one end of which is fixed on the tuner fixture and the other end is fixed on the pan surface, mainly to prevent the tuner from shaking. The reinforced edge strip is made of plexiglass, and its bending part is heated by soldering iron. ctvro.cn
ctvro.cn
Self-made bakelite desk lamp antenna bracket c
Tvro.cn4, the bracket is made of steel plate.
The characteristic of this method is that it is very convenient to adjust the focal length and elevation angle, because the method of opening strip holes and multi-point round holes in various adjustment parts is adopted, which is simple and firm in structure and convenient to obtain materials, but the structural parts need to be made by themselves, which is time-consuming and can be used inside and outside the balcony.
(1) The main steel plate of the fixed antenna is 1-2mm thick, 100mm wide and 450mm long. Bend 45o at the joint with the elevation adjustment steel plate 50mm, drill two M4 holes, bend 45o at the front end of the main steel plate 16mm, drill two M4 screw holes, and fix with.
(2) The elevation adjustment steel plate has a thickness of 1.5mm, a width of 100mm and a length of180 mm. A strip hole with a width of 4.2mm and a length of 95mm is opened at 28mm on both sides to adjust the elevation angle of the antenna.
(3) The elevation adjustment steel plate and the base connector are made of 25×25mm long 200mm angle steel. It is also possible to lengthen the steel plate of the column, and then bend the steel plate by 90o or 20mm, so that this member can be omitted.
(4) The column is made of angle steel, with a thickness of 1- 1.5mm and a length of 220 mm It can also be made of steel plate bent by 90o. One end of the column is inclined 10o at the joint with the main steel plate of the fixed antenna, and then it is bent by 90o, and the other end is bent by 90o. One or two M4.2 holes are opened at the bend to connect with the main steel plate.
"pot" debugging.
(5) Fix the tuning bracket of the tuner, select a steel plate with a thickness of 1- 1.5mm, a width of 40mm and a length of 2 10mm, and bend 90o at both sides of 10m. A row of M4.2 round holes or strip holes are opened in the middle of the bracket to adjust the focal length of the tuner.
(6) According to the fixed position of the tuner, the bracket of the tuner is made of 1mm steel plate. This clip is connected to the adjusting bracket and can also be used to adjust the focal length of the tuner.
When this antenna is used for one-pot reception 138oE and 146oE, the plastic fixture of the tuner can't be used, because the two tuners are close together and can only be made of aluminum alloy bars or steel bars. The antenna is placed on the flower stand outside the balcony, and the bottom is fixed with the scrapped computer case shell. With such a small antenna, the wind resistance is very small and smooth.
5, the production of wall bracket
When a small antenna is installed on a wall, it is usually installed outdoors. This installation method is very popular because it does not occupy indoor space. This self-made bracket can be installed on the floor or on the wall.
The main job is to make a set of universal structural parts, which can be easily adjusted up and down, left and right. The universal structural components of the bracket are made of plastic rods or bakelite rods. After the elevation and azimuth are adjusted, it can be tightened with M6 screw. The antenna and the universal structure are connected by M4 screws. Steel bars with a width of 20mm, a length of 400mm and a thickness of 1-2mm are bent at 160mm, and there are some radians on both sides, which are used to fix the antenna and high frequency respectively.
The pipeline can be a tap water pipe or a stainless steel pipe, and its inner diameter can be consistent with the outer diameter of the universal rotating part. The two ends outside the tube are fixed with screws. A square plate of 100× 100mm is welded at the bottom of the pipeline, and m7 holes are opened at the four corners to fix the antenna. The length of the pipe is related to the size of the antenna. If the antenna is 300mm, the pipe length is 160.
Self-made antenna
Fabrication of 1 and 300mm "feed-forward" antennas
(1) First, an iron box is made of steel plates, with a thickness of 4mm, a width of 50mm and a length of 10 10mm, which is rolled into a circle by a bending machine and welded at both ends.
(2) manufacturing the quasi-template of the antenna curved panel. The radian of this template refers to Taiwan Province Zhongwei 350mm offset feed antenna, and its transverse curved surface is cut, hollowed out and filed by plastic plate. Try and repair it until it matches the transverse surface of Taiwan Province Zhongwei 350mm offset feed antenna.
(3) Cut an aluminum plate with a thickness of 320×320mm 1-2mm, or choose a steel plate with a thickness of 0.5mm-0.7mm, put it on an iron hoop, and beat it with a wooden hammer for rough machining. After basic forming, finish machining with calibration template. At this time, it is necessary to choose a rubber hammer to try while knocking, and finally make the curved surface of the antenna match the calibration template, and knock it by hand.
(4) Draw a circle in the center of the processed antenna with a compass with a radius of 150mm, cut off the redundant edges along the outer circle with scissors, deburr and correct with a file, or spray your favorite color or pattern on the antenna surface, so that the antenna is basically processed. (Thanks to Teacher Song Youquan for providing the above information)
Practical application effect of antenna for small pot cover
The cost of homemade pot cover antenna is not high. Pot noodles can be bought at the grocery store. Ordinary enamel cooking pot cover 3-4 yuan, the bracket steel plate material can be bought in the scrap shop, about 3- 10 yuan. However, the most important thing for self-made antenna is miniaturization and practicality, not price and cost. Generally speaking, this small antenna is suitable for high-power direct broadcast satellites. After many pot cover experiments, we chose several practical pot covers as antennas. The first choice is the pot cover, with a diameter of 296mm, an effective receiving diameter of 280mm and a pot edge of 8mm, which is flat and the signal cannot be reflected to the feed. The curved surface of this pot cover is relatively flat, the depth of the pot surface is 26mm, and there are only 1 reinforcing rings in the middle. If you can't buy a pot cover with this shape, you can buy another pot cover with a diameter of 324mm and an "effective diameter" of 294 mm If a pot has multiple satellites, its efficiency is close to the former, but it is easy to buy, and a single satellite receives a pot cover of more than 296 mm.
One thing to note here is that the parameters in the following table are for reference only, but they can be used for comparison. It should be noted that the recorded parameters are closely related to weather, receiver threshold, tuner, local signal field strength, antenna installation environment and debugging accuracy.
The antenna, 138 as the primary focus and 146 as the secondary focus, can be watched normally in rainy days, and the picture is smooth. When it rains, if there are no beads on the pot surface, you can watch it normally. At this time, you can use this antenna on an uncovered balcony. In sunny weather, when you receive it on the balcony through a 1 5mm thick window, the signal quality will drop by 8%, and the picture can still be viewed smoothly. When passing through two layers of 5mm thick windows, the signal quality drops 14%, and some transponders appear mosaic, but the transponders with strong signal can still watch normally. The specific signal quality of the antenna when receiving two stars on sunny days. The receiver is CP-7885,
When the signal quality is full, it is 100%. After several months, it was used normally, achieving the goal of practical miniaturization.
The antenna with a diameter of only 230mm was cut with scissors on the original basin surface with a diameter of 290mm, and the depth of the basin surface was 18mm, in order to test the limit of the minimum diameter of the antenna. When a single satellite receives two satellites, 138oE or 146oE, the signal quality still has some room and the picture is smooth. When placed on an outdoor balcony or indoor windowsill, a single satellite receives these two satellites. When 138oE or 146oE, it can be watched normally in sunny days, with a certain margin, smooth picture and specific signal quality. The receiver is CP-7885, the tuner is Baichang 525, and the local oscillator is 1 1.3GHz.
In the signal quality measured by the antenna, "window opening" is the data measured when the balcony opens the window. "Near" is measured when passing through 1 5mm thick glass window. When it rains, the window can still be viewed normally, which basically achieves the purpose of achieving the minimum limit of antenna aperture.
When the antenna is covered with a cover, a single satellite receives data.
Some rules can be summarized from the depth of various pot covers: generally speaking, the depth of pot surface is about 9% of the diameter, so try to choose a pot surface with shallow depth and flat transition surface, and the foundation efficiency is relatively high. In addition to receiving 138oE or 146oE, this antenna can also receive programs on Palapa -C2 satellite of13oe, in which the signal quality of this group of transponders at 1 1472Mhz is 55%./kloc. The data of these two groups of transponders were measured before the live operator of 1 13e Palapa -C2 satellite stopped broadcasting, and the pictures can be viewed smoothly. We also tried to receive CIGNA 1, and the signal quality was 12780V4 1530-44% respectively. 12440 V 4 1530, 12500 V 4 1530, 12560 V 4 1530 are all 36%,12620.
This kind of small antenna has a good prospect and practical value in the application of high-power direct broadcast satellite in the future.
The measurement data of the antenna is measured on the balcony. The receiver is Aero 430 and the tuner is Baichang 525( 1 1.3GHz).
The measured data watched by the antenna were measured outside the balcony. The receiver is CP-7885, and the tuner is Baichang 525, 1 1.3 GHz.
76.5 degree Asia-Pacific 2R sample fitting
The antenna can only receive one set of 12375Mhz Tibet station, and the signal quality is 55%, and everything else is 0, so we have to give up. The author chose a 380mm aluminum pot cover for the experiment, and most of the transponders can receive it, but the margin is not large. The signal-to-noise ratios of the two sets of transponders are 24, 25, 26 and 27, respectively, and the measured data are measured on the balcony. The receiver is Aero 430, and LNB is not 100. The purpose of this experiment is only to see its effect, and it cannot be used for normal reception.
Some feelings after the experiment
We were deeply impressed by the experiment of making antenna with pot cover, aluminum plate and galvanized plate, and we also felt the joy of success, which proved that there are still many potentials to tap the benefits of antenna, such as the radian of curved surface, different materials and the length of focal length. I have seen 0.45-0.75m offset feed antennas and flat antennas of Sony, Toshiba, Buddy, Panasonic, Aiwa, Gosbell and other brands, and they are all beautifully made. We have also used some imported brands of offset feed antennas, and the technology and packaging are exquisite and impeccable. Its efficiency is indeed higher than that of domestic antennas with the same caliber, and its focal length is relatively short, and its accessories are also very thoughtful, such as tuners, cables, F-heads and tools. The fixture is also omnipotent, suitable for fixing in many occasions and environments, and users can install it according to the drawings after buying it back. The author uses the imported second-hand antenna of 0.45m to receive programs on the 76.5oE Asia-Pacific 2R, and 1 1 transponders all receive normally. Although some transponders have little signal quality margin, the picture is still very smooth, and the domestic 0.45m antenna can't be downloaded at all.
There are more than 100 antenna factories in China, and the number is increasing. However, few factories have the ability to test antenna performance and technical indicators, and the production technical standards of each company are the same, copying from the east to the west. At present, the offset feed antenna produced in China has a minimum aperture of 450mm, a focal length of 270mm, a disk aperture of only 296mm and a focal length of only188 mm; ; The diameter of the pan surface is only 230mm, and the focal length is only 179mm, which is really super small. The minimum diameter of domestic feed antenna is 1000mm, which can not meet the needs of users. Moreover, the quality products produced by factories are few, and most factories are unwilling to invest in scientific research and development. Many antenna molds are copied, with materials cut corners, rough technology, low efficiency and short service life. This may be the result of a vicious circle of price competition. In the previous quality appraisal, there were many unqualified proportions. I hope this article can inspire antenna manufacturers: if manufacturers can increase investment in R&D design, control good materials, work hard on antenna caliber and efficiency, and improve production technology, then high-gain boutique antennas will definitely appear in domestic and foreign markets, and high-efficiency small antennas will not be a dream.