Aim the feedhorn to face the parabolic re f l e c t o r. With an open feedhorn, turn the
open end (the other end is closed) toward the satellite dish. With a closed feed-
h o rn, turn the plastic-covered end (the other end is metal) toward the dish.
Note that the antenna inside the feedhorn must be mounted in a vertical position
for GOES (U.S.) satellite reception and in a horizontal position for METEOSAT
( E u ropean) satellite reception. Enclosed feedhorns are marked horizontal and vert i-
cal. The placement of the antenna must be correct to receive the desired signal.
f i g u re 60.
D o w n c o n v e rt e r
A downconverter is required to convert geostationary satellite signals to a form that
can be used by the computer. Power is supplied to the downconverter by either a sep-
arate 12-volt source applied directly to the unit or by the receiver. The downconverter
is housed in a weather-proof case with predrilled mounting holes and connected to
the feedhorn with coaxial cable. Typically, the signal strength from a downconverter is
high enough to permit the use of a smaller diameter cable between the downconvert-
er and receiver. Cable runs of less than 200 feet may use a cable such as Belden 9311.
Longer runs should use Belden 9913.
Antenna feedline
The antenna feedline is perhaps the most important component in a ground station.
A good feedline will provide maximum signal while reducing stray radio fre q u e n c y
(RF) or man-made noise (interf e rence). Coaxial cable is feedline whose center con-
ductor has been encased in dielectric material with an outer braided shield. The
shielding greatly reduces the introduction of RF or man-made noise into the re c e i v-
ing system. Avoid inexpensive cable that will not provide adequate shield or lasting
c o n s t ru c t i o n.