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How to check a C-BAND or Mini dish LNB
The classic symptom of a bad LNB is you are able to get all your satellite
receiver screen graphics to appear on your TV but you have no satellite channel
picture.
First, if there is nothing on the channel your are on this symtom is what you
will get and there is nothing wrong. If you get this symtom and there should be
something on the channel you are watching you need to check out your LNB
system. The coax line coming from the actual LNB mounted on your dish antenna
and going to the LNB input on the back of your satellite receiver has a voltage
on it. This voltage is used to power the LNB. On a C-BAND system the voltage is
18 Volts DC. On a Mini Dish system the voltage switches between 18 Volts and 14
Volts depending what polarity the channel you are watching is on. You need to
get out your low cost Volt OHM Meter and go to your antenna remove the coax
from the LNB and check the voltage to see if you have the required voltage on
the coax. If you have the required voltage you either have a bad LNB or your
dish is not aimed at the right satellite or the channel you are on has nothing
on it. If you do not have the required voltage your LNB is probably ok. If you
did not have the required voltage you either have a problem in the coax or the
receiver. Next check for the required voltage at the back of the receiver use a
short jumper coax cable attached to the LNB input terminal on the back of your
receiver to measure the LNB voltage at the receiver, this will tell you if the
problem is the receiver or the coax.
Please note there can be no splitters in the LNB coax
only diplexers. Splitters will not let the voltage needed by the LNB travel up
the cable, a diplexer will. When checking coax for problems be sure to check
for shorts between the center conductor and the outside conductor, sometimes
those super thin aluminum wire braids that are part of the outside conductor
have been known to be shorting out to the center conducter, this is because
they are so small it is hard to see them.
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We hope this helps you.
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These directions are as is, no warranty implied.
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