72
TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine
— 07-08/2013
—
comparison is directly cor-
related to signal quality. The
greater the MER, the better
signal quality and greater
margin for poor weather
conditions. Taking into ac-
count that the SUS 21 F has
to convert the signal from
its “normal” position in L-
band either to 1076 MHz or
to 1178 MHz, we expected
that we would notice a sig-
nificant degradation of MER
because every conversion
always introduces additional
noise. But, no! For the ma-
jority of transponders there
was no difference at all. Only
for the DVB-S2 transponders
broadcasting with the high-
est symbol rate (30 Ms/sec)
we observed slightly worse
performance. For the most
popular 27.5 Ms/sec tran-
sponders, the MER was un-
affected.
On the other extreme, at
the lowest symbol rates (2.5
Ms/sec), the SUS 21 F per-
formed brilliantly. We no-
ticed no difference in MER
between LNB output and sin-
gle cable router output.
The test would not be
complete if we did not try to
connect a real receiver and
zap channels. Every tran-
sponder and every channel
that our receiver was able to
process when connected to a
regular LNB was also avail-
able in the single cable net-
work even though we used a
subscriber socket introduc-
ing extra 14 dB attenuation.
Transponders with very low
and very high symbol rates
(2.5 through 30 Ms/sec)
were available without any
problem.
It is worth knowing that
channel zapping speed can
be affected in a single cable
network because when you
change a channel from one
transponder to another, a lo-
The description reveals
also additional functions of
the SUS 21 F: possibility to
include terrestrial signal in
one of the satellite input and
possibility to power it from
an external optional power
supply unit. Normally, the
SCR is powered by the re-
ceivers connected to its out-
put and no optional PSU is
needed at all.
The SUS 21 F has one mul-
ticolor LED indicator showing
device status and error con-
ditions. If the supply voltage
from a receiver is too low or
too high, you will know it.
You will also be notified if a
short circuit is detected in
the output cable.
We used our 85 cm offset
dish for Ku-Band with a Twin
LNB aimed at EUTELSAT16A
on 16° East. Because this
satellite had low and high
symbol rate transponders,
we were able to push the
SUS 21 F to the limit. To
make the test even harder,
we used a 50 meter long co-
axial cable (about 13 dB at-
tenuation) and a flat cable
window coupler (another 2
dB attenuation). We started
our test with observing the
output signal of the SCR
on the spectrum analyzer
screen. It looked perfect.
Except for the modulated
carriers on 1076 MHz and
1178 MHz there was nothing
else. Carrier to noise ratio
was in excess of 30 dB!
After such successful be-
ginning, we decided to first
measure the signals routed
directly from the Twin LNB
(we marked them as REF
1 and REF2) and then con-
nect the SUS 21 F to the
LNB and measure the signals
available at its output (Slot
1 and Slot 2) on 1076 MHz
and 1178 MHz. As expected,
the channel power (signal
strength) varied significantly
when the signal was taken
directly from the LNB and
was almost constant for ev-
ery transponder when single
cable router was used. The
Automatic Gain Control cir-
cuit of SUS 21 F did its job
very well indeed.
The second important pa-
rameter, Modulation Error
Ratio, that we used in our
