Home >> April 2009 Edition >> FOCUS: Plan B... For Continuous Signal Reception
FOCUS: Plan B... For Continuous Signal Reception

by Jörg Schmidt, DEV-Systemthechnik

Black screens and complete audio dropouts around the world for 18 minutes; what sounds like a scenario from the Stone Age of live broadcasting became a reality for the 29.46 million TV viewers who wanted to watch the Euro semi-final between Turkey and Germany in the summer of 2008.

This happened to be a glitch that resulted in the European Football Association, UEFA, having to pay a seven-figure compensation to the members of the European Broadcasting Union (EBU). In this case, the interruption was caused by a power failure at the broadcast centre in Vienna. A failure of one or several antennas in a headend could also have similar consequences, in which operators will be held accountable. An automatic antenna redundancy system, however, would ensure you were on the safe side.

A thunderstorm with heavy rain and squalls had knocked out the broadcast centre’s technology in Vienna. Headend operators suddenly faced a scenario similar to the one just described — if a thunderstorm knocked out even just one antenna, transmission problems — the screen stays black until the damage has been repaired.

The repair of roof antennas is particularly tricky and dangerous, especially with a thunderstorm raging outside. And what if the antenna is snapped off by the wind? Sometimes it is only the antenna’s low noise block (LNB) that is broken — whatever the cause, headends should have a proper backup system in place in order to ensure uninterrupted service.
Just To Be On The Safe Side
However, it would be absolutely uneconomical, in particular for large headends, to purchase a replacement antenna for every single antenna used. Individual solutions are complex to develop and, therefore, rather costly.

What does it take to find an easier and less expensive solution? What is needed is a comprehensive and automatic system that monitors the RF signals of several stationary antennas, a solution that uses a motorized antenna as backup. The motorized antenna then replaces the defective antenna, if needed.

This solution is an automatic antenna redundancy system that is comprised of a motorized antenna, a redundancy switch, and a control unit that connects, queries, and controls the two elements. First, the actual signal strength is compared with the preset threshold at the input of the redundancy switch. If the received signal strength drops below the threshold value, this is reported to the Antenna Monitoring and Control System (M&C) by the control unit, which then analyzes where the error message was generated.

The motorized antenna is then directed at the same satellite the defective antenna was targeted upon and takes over the transmission. As the management systems of a headend are not designed to control antennas, this is automatically done by the antenna redundancy system.

The RF signal handling expert from DEV Systemtechnik has developed the antenna redundancy system N+1, which offers an all-in-one solution for large headends. As many as 16 antennas can be replaced by the motorized antenna. Furthermore, the solution comprises a scalable two-stage system, i.e., 2+1, 4+1, 6+1, and so on. This makes for a highly flexible solution unmatched on the market.

In addition, an individually configurable information interface provides for communication with the headend’s management system so the user is able to control the current status of the subsystem. As a result, the management system provides information on the faulty antennas, from which satellite the motorized backup antenna will be receiving its signals, and when it has been activated. The entire process from the failure of an antenna to the analysis of the signal, and from the adjustment of the backup antenna to switching to headend reception, is carried out automatically. If required, every step can also be done manually.

A Reliable, Economic Solution
The antenna redundancy system offers headend operators an entirely new range of opportunities for efficient operation and business management. Until now, the only answer to the problem of antenna failure has been to manually set up and adjust a replacement antenna or to develop an individual, but rather expensive solution. The antenna redundancy system provides operators with a readily available and established system that comprises fully coordinated components, and that allows communication with almost any management system. Further configuration for other sections of the transmission path can be provided upon request.

A quicker and easier way to ensure reception in case of antenna failure does not exist. The automation of redundant antenna concepts and their integration into the management systems of headends allows, at the same time, to significantly reduce the overhead for backup services. And, last but not least, TV viewers can be assured antenna failure will not be an issue during the next broadcast of a football cup.