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140 141TELE-satellite International — The World‘s Largest Digital TV Trade Magazine — 09-10/2012 — www.TELE-satellite.com www.TELE-satellite.com — 09-10/2012 — TELE-satellite International — 全球发行量最大的数字电视杂志

Lego Antenna

•Evenfive-year-oldkidscanbuildasatellitesystem(ifDadhelps)•Youcanmakeyourownparabolicdishoutofaluminumfoil•Installationonabalconyisonlygoodonthosedayswhenthewindiscalm•LegoAntennalifespan?NomorethananhoursincebythenyourdaughterwillwanttobuildsomethingelsewiththeLegobricks•Aninterestingwaytospendtheafternoonwithyourkids

Satellite reception system made from Legos and aluminum foil.

Selfmade Dish

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142 TELE-satellite International — The World‘s Largest Digital TV Trade Magazine — 09-10/2012 — www.TELE-satellite.com

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 power-ful DTH satellites have be-come. In Europe those sat-ellites would be ASTRA and HOTBIRD. To demonstrate how simple it really is to re-ceive a satellite signal and since I had already commit-ted to spending some time with my daughter in the af-ternoon, 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 still flat aluminum foil had to be molded into a parabolic form. Since a simple imprint from anoth-er antenna was out of the question – that would have been cheating – the follow-ing 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 spi-ral 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 sever-al times. If it hasn’t quite reached its parabolic shape, simply roll the ball in a spi-ral fashion across the foil again. By testing the shape several times, you avoid ac-cidentally over shaping the foil in which case you’d have to start over from the be-ginning. 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. sat-ellite 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 relation-ship. 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 tran-sponders. By repositioning the LNB, you’ll find the best

The materials needed for the Lego antenna: building blocks from my daughter and a roll of aluminum foil from the kitchen.

Selfmade Dish

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144 145TELE-satellite International — The World‘s Largest Digital TV Trade Magazine — 09-10/2012 — www.TELE-satellite.com www.TELE-satellite.com — 09-10/2012 — TELE-satellite International — 全球发行量最大的数字电视杂志

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 trans-missions are turned off: while an analog receiver allowed you to align an an-tenna in real time, a digital receiver brings with it a rel-atively large delay. It’s no wonder that more and more satellite signal analyzers are appearing on the mar-ket! The real-time spec-trum display on an analyzer identifies signals before the tuner in the receiver has a chance to process the sig-nals. Unfortunately, most low-end signal analyzers don’t have a spectrum dis-play or it’s extremely slow and therefore not quite suitable for such an experi-ment. 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 re-flector provide sufficient gain in the antenna so that both analog and digi-tal transponders can be received. There were no problems receiving ASTRA although it needs to be mentioned that this small antenna has no bad weath-er 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 mod-ern DTH satellites really are and how LNBs and tuners have become such high-quality items. The time went by very fast that af-ternoon and my daughter got a small peak into the fascination of satellite re-ception!

Just before assembly: the antenna made from Lego blocks, the parabolic shaped aluminum foil and the signal analyzer with attached LNB.

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146 TELE-satellite International — The World‘s Largest Digital TV Trade Magazine — 09-10/2012 — www.TELE-satellite.com

Making a Parabolic Dish out of Aluminum Foil

1. 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 para-bolic 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.

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148 TELE-satellite International — The World‘s Largest Digital TV Trade Magazine — 09-10/2012 — www.TELE-satellite.com

1. The Lego antenna without reflector and without LNB.2. The Lego antenna from behind.3. No problems with recep-tion according to the signal analyzer.