Pagina 142 - TELE-satellite - La Più Grande Rivista del Mondo Sul Commercio TV Digitale

Versione HTML di base

TELE-satellite International — The World‘s Largest Digital TV Trade Magazine
— 09-10/2012
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
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
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
Selfmade Dish