The Low Noise Block device on the end of a satellite dish arm receives the satellite broadcast signal collected by the dish and pipes it to your satellite receiver through a run of coaxial cable. LNBs can degrade over time, particularly in locations exposed to extreme weather conditions. Signs of a faulty LNB include missing satellite television channels, video pixelation, signal drop-out during heavy rain or the complete loss of signal. To troubleshoot an LNB, first visually check the device and then test the signal levels with a digital-satellite signal meter.
Switch off the satellite TV receiver and disconnect it from the main power supply outlet. Satellite receivers send a low voltage charge up the coaxial cable to power the LNB, so always disconnect the power before checking an LNB.
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Climb to the location of the satellite dish with steps, a ladder or a raised platform.
Find the LNB unit on the end of the dish arm. The LNB is usually horn-shaped, cylindrical or rectangular.
Inspect the plastic casing that encloses the electronic components of the LNB. If the casing is warped or cracked, you will need to replace the LNB, because water ingress will have damaged the electronics inside the casing.
Slide down the rubber boot that covers the coaxial cable connector's joint with the LNB output jack. Gently tug the cable to ensure that the joint is firm and secure. If the joint is loose, frayed or corroded, you will need to replace the connector and screw it back into the jack. If the LNB jack has rusted, you will need to replace the LNB device. If you can't see any problems with the casing, output jack or cable connector, you can now test the output signal level.
Unscrew the existing coaxial connector on the down lead from the LNB's signal output jack. Screw the supplied coaxial cable fly-lead into the "Input" socket of a battery-powered digital-satellite signal meter. Screw the other end of the fly-lead into the output jack on the LNB.
Read the signal level on the signal meter. Displays vary by signal meter type, including dial displays, LED signal level indicators and LCD digital read-outs. No signal or a low signal strength/quality reading indicates that the LNB is not functioning correctly and you will need to replace the device. A medium- or high -strength/quality reading indicates that the LNB is working correctly and the fault lies elsewhere in your satellite television system.