It is a very specific and confusing problem for TV viewers: you sit down to watch TV and find that while RTÉ and BBC are working perfectly, Sky Sports and Discovery are displaying the dreaded "No Satellite Signal" message. How can the system be broken for some channels but work perfectly for others? It defies logic. Surely if the dish was broken or moved, everything would be gone?
The answer lies in how satellite signals are transmitted. To fit thousands of channels onto the satellites, broadcasters use two different "polarizations"—Horizontal and Vertical. Your dish switches between these two modes thousands of times a second depending on the channel you select. If a specific component in your system fails, it can get stuck on one mode, effectively blinding you to half the channels available. This requires specialist Sky Tv Repairs to identify the faulty switching component and restore the full spectrum.
The Role of the LNB Voltage
The LNB (the receiver on the arm of the dish) is powered by the Sky box inside your home. The box sends a small voltage up the coaxial cable to tell the LNB what to look for. Usually, 13 volts tells it to look for Vertical signals, and 18 volts tells it to look for Horizontal. If your LNB is failing due to age or water ingress, it might stop responding to the 18-volt command. It gets stuck on Vertical. Therefore, you can watch all the Vertical channels perfectly, but every Horizontal channel is dead. A simple multimeter test by an engineer can confirm if the LNB is switching correctly.
Cable Resistance and Voltage Drop
Sometimes the LNB is fine, but the cable is the issue. If the cable run is very long, or if the copper core has corroded due to water ingress (blackening the wire), the voltage drops as it travels up to the dish. The box might send 18 volts, but only 14 volts arrives at the dish due to the resistance. The LNB gets confused by the low voltage and defaults to Vertical mode. This is why you might lose channels gradually over time as the corrosion worsens. Replacing the cable with high-quality, pure copper coaxial cable ensures the correct commands reach the dish every time.
Power Supply Unit (PSU) Failure
In older Sky boxes, the internal power supply unit can start to fail. The capacitors bulge and leak, meaning the box can no longer generate the full 18 volts required to switch the LNB. In this case, the fault lies with the box itself, not the dish. An experienced engineer will test the output at the back of the box before climbing any ladders. If the box is under-powering the system, it needs to be replaced or repaired. This diagnosis saves you from replacing a perfectly good dish unnecessarily.
Interference on Specific Frequencies
Occasionally, a specific device in your home (like a DECT cordless phone or a router) can emit interference that blocks just one polarization or frequency band. This is rarer, but it happens. The interference "drowns out" the weaker Horizontal signals. A spectrum analyser can visualise this invisible noise. Moving the interfering device or upgrading the satellite cable to a better-shielded version usually clears the problem instantly, bringing back your missing channels.
Conclusion
Losing half your channels is a sign of a specific technical failure, not just bad luck. By understanding the science of polarization, we can pinpoint the fault and get your full channel list back up and running quickly.
Call to Action
Missing your favourite channels? Call us to fix polarization faults and restore your full service.
Visit: ; https://www.smartsatconnect.ie/
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