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TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine
— 01-02/2013
—
Testing the
two samples of
Jiuzhou Twin LNBs
Skytrack JTU41
the quality of cable connec-
tion will be not degraded
over time. Their weight is
not high so they are suita-
ble even for the dishes with
not so strong LNB supports.
Also their energy consump-
tion is moderate – 130 mA
in our measurements, so it
will not be a problem for any
receiver or antenna switch.
Workmanship leaves noth-
ing to be desired for this
class of products.
We usually test this kind of
LNBs with one of the strong
European satellites – ASTRA
on 19.2° East or HOTBIRD
on 13° East as this is the
most typical application for
them here in Europe. This
time, however, we decided
to make our test a little bit
harder. We chose TURKSAT
on 42° East. Some of its
transponders are quite weak
in our location and addition-
ally some of them transmit
with low symbol rates. This
makes the test more de-
manding.
The table below (Table 1.)
lists all the transponders we
used for our test. Symbol
rates vary from 2,500 up to
30,000 ks/sec and there are
transponders of both polari-
zations from low and high
sub bands of the Ku-Band.
We turned our dish to
TURKSAT and did the first
round of measurements with
our reference high perfor-
mance single LNB. Then, we
installed the first sample and
measured its two outputs
(1A and 1B in our graphs).
Finally, we did the same with
our second sample of the
JTU41 (2A and 2B).
In our analysis we fo-
cused on the output power
achieved from the same
transponders; this corre-
sponds to the LNB conver-
sion gain parameter and
modulation error ratio (MER)
which in turn corresponds
to a combination of a few
parameters: noise figure,
phase noise, isolation, im-
age rejection and intermod-
ulation. In other words, the
first parameter tells us how
strong the signal is and MER
is a measure of signal quality
at the output of LNB.
The first graph shows
