Lego Antenna. Selfmade Dish. 140 TELE-satellite International The World s Largest Digital TV Trade Magazine 09-10/2012

Transcription

1 Selfmade Dish Lego Antenna Satellite reception system made from Legos and aluminum foil. Even five-year-old kids can build a satellite system (if Dad helps) You can make your own parabolic dish out of aluminum foil Installation on a balcony is only good on those days when the wind is calm Lego Antenna lifespan? No more than an hour since by then your daughter will want to build something else with the Lego bricks An interesting way to spend the afternoon with your kids 140 TELE-satellite International The World s Largest Digital TV Trade Magazine 09-10/ /2012 TELE-satellite International 全球发行量最大的数字电视杂志 141

2 Selfmade Dish A passionate satellite DXer plays with his daughter and uses Legos to build a satellite antenna! Vitor Martins Augusto Today, in an industry that consistently offers LNBs with lower and lower noise figures and where satellite receivers are getting more and more sensitive, you tend to forget how powerful DTH satellites have become. In Europe those satellites would be ASTRA and HOTBIRD. To demonstrate how simple it really is to receive a satellite signal and since I had already committed to spending some time with my daughter in the afternoon, I decided to make the best of things and use her Lego blocks to build a Lego satellite antenna with my daughter. The reflector was made out of aluminum foil that I borrowed from my wife in the kitchen. For the reflector three layers of aluminum foil were folded together resulting in a fairly stable square. The materials needed for the Lego antenna: building blocks from my daughter and a roll of aluminum foil from the kitchen. The still flat aluminum foil had to be molded into a parabolic form. Since a simple imprint from another antenna was out of the question that would have been cheating the following technique was used: you take the flat aluminum foil and lay it on a couch or mattress or on some other soft surface. Then you take a smooth ball and roll it on the aluminum foil in a spiral fashion from the center to the outside. Repeat this procedure several times without exerting too much pressure. The result is a parabolic form. For best results, test the aluminum foil several times. If it hasn t quite reached its parabolic shape, simply roll the ball in a spiral fashion across the foil again. By testing the shape several times, you avoid accidentally over shaping the foil in which case you d have to start over from the beginning. To secure the foil, a mount is built using the Lego blocks. This serves two purposes: first of all the mount has to support the aluminum foil (i.e. satellite dish) so that it can be set to the proper angle and doesn t fly away or become deformed with the slightest breeze. Second, it serves as a mount for the LNB. Of course, it has to be placed at the proper offset so that it sits in the focal point of the antenna. It was surprising how close the LNB was placed to the aluminum foil. Since the foil was shaped by hand using a ball, it has a larger curvature to it compared to a standard antenna. This changes the f/d relationship. Don t be fooled by this; it s better at first to have the LNB too close to the foil instead of too far away! Through trial and error and with the help of a signal analyzer it shouldn t take long to find the first transponders. By repositioning the LNB, you ll find the best 142 TELE-satellite International The World s Largest Digital TV Trade Magazine 09-10/2012

3 possible position so that the construction of the Lego mount can be completed. Manual formation of the aluminum foil was always necessary in order to obtain the best possible results. During the alignment of the Lego antenna, you ll notice a huge disadvantage when analog satellite transmissions are turned off: while an analog receiver allowed you to align an antenna in real time, a digital receiver brings with it a relatively large delay. It s no wonder that more and more satellite signal analyzers are appearing on the market! The real-time spectrum display on an analyzer identifies signals before the tuner in the receiver has a chance to process the signals. Unfortunately, most low-end signal analyzers don t have a spectrum display or it s extremely slow and therefore not quite suitable for such an experiment. Of course it would be nice to have a professional analyzer at hand. The further fine-tuning of the antennas alignment along with the manually shaped aluminum foil reflector provide sufficient gain in the antenna so that both analog and digital transponders can be received. There were no problems receiving ASTRA although it needs to be mentioned that this small antenna has no bad weather reserve and also that it shouldn t be mounted on a balcony or terrace if it s a windy day outside. This experiment clearly shows how powerful modern DTH satellites really are and how LNBs and tuners have become such highquality items. The time went by very fast that afternoon and my daughter got a small peak into the fascination of satellite reception! Just before assembly: the antenna made from Lego blocks, the parabolic shaped aluminum foil and the signal analyzer with attached LNB. 144 TELE-satellite International The World s Largest Digital TV Trade Magazine 09-10/ /2012 TELE-satellite International 全球发行量最大的数字电视杂志 145

4 Making a Parabolic Dish out of Aluminum Foil Three layers of aluminum foil were folded on top of each other to form a square and then placed on a soft surface (here: carpet). 2. A smooth ball (also obtained from my daughter s stash of toys) is rolled in a spiral fashion on the surface of the aluminum foil starting from the center and moving to the outside in order to form a parabolic shape. 3. Next the curved aluminum foil is secured to the antenna mount. It s a good idea to do this on calm days otherwise the reflector could blow away in the wind. 146 TELE-satellite International The World s Largest Digital TV Trade Magazine 09-10/2012

5 The Lego antenna without reflector and without LNB. 2. The Lego antenna from behind. 3. No problems with reception according to the signal analyzer. 148 TELE-satellite International The World s Largest Digital TV Trade Magazine 09-10/2012