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1 -12/2012 —
TELE-satellite International —
全球发行量最大的数字电视杂志
eastern and western ends is in the
same direction or in opposite direc-
tions, it can be determined what needs
to be adjusted.
Sometimes the entire motor and an-
tenna assembly needs to be turned to
the left or the right, in other cases the
elevation of the motor has to be cor-
rected. Since the entire satellite arc
must be checked out with each adjust-
ment to see if reception for all the sat-
ellite positions got better or worse, this
process can take quite a bit of time.
And when the antenna and motor are
finally adjusted perfectly such that eve-
ry satellite position has the best pos-
sible signal reception, it is almost guar-
anteed that this process will have to be
repeated after the first storm.
Some time ago I came up with an idea
to solve this problem; finally I acted on
this idea. What would happen if two mo-
tors were used instead of one? The two
motors would be offset by 90 degrees
so that the second motor would drive
the first motor along with the attached
antenna up and down. A fine-tuning ad-
justment of the antenna would no long-
er be necessary; the antenna assembly
could simply be adjusted up or down for
each satellite position.
And this is exactly what I implement-
ed for this workshop. First I obtained
two Moteck SG2100A motors. These
motors have come to be known as ex-
cellent motors: they are inexpensive,
high-quality and have a long-life. This
motor has been driving my main an-
tenna for five years now and there has
never been a problem.
My first problem was that I might
need to purchase extra adapters or
have some custom made for me to
mount the two motors to each other. I
tested it out on the drawing table and
wouldn’t you know it: it is essentially
possible, as can be seen in the pictures,
to mount one motor at a 90 degree an-
gle to the other without the need of any
extra accessories! From a mechanical
point of view, there was no longer any-
thing in the way of this experiment.
For this experiment I used my test
antenna – a 60 cm offset dish – that
is normally mounted on a moveable
stand. The SG2100A can move dishes
as large as 120 cm in diameter. In this
case, however, I don’t recommend us-
ing a low-cost antenna made out of
steel; they are simply too heavy. It
would be far better to use a name-
brand antenna made out of aluminum.
The two motors were mounted on the
stand’s mast and then the antenna was
mounted to Motor 1. Motor 1 handled
the east/west movement of the anten-
na while Motor 2 handled the up/down
movement of the assembly.
The electrical switching also had to
be figured out but it quickly became
clear that only one DiSEqC 2/1 switch
and a twin LNB would be needed and, of
course, the necessary LNB cables.
The DiSEqC 2/1 switch is to be used
to switch between Motor 1 and Motor
2.
A twin LNB needs to be used so that
you can still receive a satellite signal
independent of the DiSEqC setup. The
two outputs of the LNB are connected
to the inputs of the two motors. And as
far as the LNBs go, it would certainly
make sense to use high-quality twin
LNBs for this project.
Pay close attention to the power us-
age since the tuner will be loaded down
with the switches, motors and twin
LNB. The reception capabilities of the
LNB should also be sufficient. In this
test it was interesting to discover that
the two LNB outputs provided differ-
ent levels of signal quality. With that in
mind, the ‘better’ output should be con-
nected to Motor 1. The result is a con-
nection diagram as shown in Figure 2.
Out of sheer curiosity I connected a
signal analyzer to the completed as-
Figure 1: Motor manufacturer Moteck offers an easy to use
calculator on their website
www.gaaps.com.tw
. It provides the
declination angle for motor alignment based on the entry of your
latitude and longitude as well as the orbital position of the desired
satellite.
Figure 2: Schematic diagram of the two-motor system. One of
the LNB outputs goes to Motor 1 while the second output goes to
Motor 2. The DiSEqC 2/1 switch is used to switch between the two
motors.