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While
digital broadcast satellite service is still lacking
some of the basic features of conventional cable (the
ability to easily split signals between different TVs
for example), its high-quality picture, varied programming
selection and extended service areas make it a good
alternative for some. With the rise of digital cable,
which also has improved picture quality and extended
channel selection, the TV war is really heating up.
Just about anything could happen in the next 10 years
as all of these television providers battle it out.
What
is an LNB?
Low Noise Block-downconvertor (so called because it
converts a whole band or “block” of frequencies to a
lower band). An LNB sits on the end of an arm and faces
the parabolic reflector (‘dish’) which focusses the
signals from a satellite into the ‘feed horn’ of the
LNB. The LNB converts the signals to a lower frequency
and sends them out to the cable connector, which you
connect to your satellite receiver via coaxial cable.
How
to test an LNB?
I think my LNB is faulty. How can I test it?
-The only way to fully test an LNB is to fit it to a
suitable dish, align the dish and LNB and connect a
satellite receiver. Then check to make sure every channel
is there. If no channels are missing and if it continues
to work through a hot day and a cold night, the LNB
is fine. However, the reverse is not true. If some channels
appear to be missing, this could be the fault of the
cable, the receiver or the dish (distorted or misaligned).
It does not prove that the LNB is faulty. So then you
need to use a process of elimination by swapping the
dish, the cable and the receiver (for a different make/model
as some receivers won’t work correctly with some LNBs).
Can’t
I test it with a meter?
A cheap satfinder meter simply looks at the average
strength of all frequencies. It will not tell you if
some frequencies are missing. An expensive meter looks
at a specific frequency (sometimes more than one) but
it will not tell you if some frequencies are missing.
Also, most meters rely on battery power. If the battery
can not supply enough current to the LNB, it may give
a false reading.
CONECTING
MORE THAN ONE SATELLITE RECEIVER TO A SINGLE DISH 
‘Twin-output’ LNB
Currently available in most shops dealing in satellite
receiving equipment, the twin output LNB provides two
outputs to feed two separate receivers for independent
working. Each output can be switched independently by
13/17 volt input by the individual receiver to change
polarisation and by 22kHz to change the band.
‘Dual
LNB’ or ‘Monobloc LNB’
This type of LNB has a single output and the actual
satellite signal is selected by the receiver which sends
a DisEqC (22kHz) pulsed tone up the LNB cable. So only
one satellite transmission can be viewed at a time.
This is in contrast with dish systems that have two
or more separate LNBs where, with two receivers, both
satellite transmissions can be viewed or recorded simultaneously.
‘Quad-output’
or ‘Quad universal’ LNB
This can feed four separate receivers. Basicaly an LNB
with four IF outputs. Each receiver has independent
control of polarisation and band via 13/17v switching
and 22kHz on/off respectively.
To
be Continued in October'07 issue
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