THE IMPORTANCE OF TESTING

THE IMPORTANCE OF TESTING INFRASTRUCTURE FOR AV

Aiden Jones, Technical Director, Blustream EMEA, underlines the importance of a safety first attitude when it comes to cables and connections.

HDBaseT uses PAM16 signaling which creates 16 voltage levels across the cable from the point of transmission to the point of receive, with 8 voltage levels on the return path. This asymmetric link can transfer up to 8Gbps of data across infrastructures designed to cope with much less.

This modulated signal will degrade dramatically over distance – even in a nearperfect environment. By the time the signal reaches the HDBaseT receiver chip over a full distance run, the eye diagram that would be seen at the start of the run, will have almost completely inter-twined. No longer will there be clearly differentiated voltage levels, but the magic of the HDBaseT receiver chipset, is its ability to take that collapsed eye diagram, and reopen it in order to recover the data encoded at each level.

Quite simply, the process of sending data to the millions of pixels on our UHD displays, multiple times per second, cannot be carried out efficiently where a cable infrastructure is compromised. As the demands of video distribution increasing as the technology evolves, the infrastructure our equipment is connected to has never needed to be as robust. This is an extremely important consideration as the performance of a cable will directly influence the performance of HDBaseT transmissions.

As a manufacturer of HDBaseT equipment, we do receive calls from integrators asking why they are experiencing issues on certain cable runs when using HDBaseT technology. We hear statements such as, “the cable tested absolutely fine”, or “I am using HDBaseT cable.” Digging a little deeper into the tests that have been carried out, there are very few that have performed a suitable test that will qualify the cable for use with a modulated signal type.

So, the ‘million-dollar’ question… What would be considered an adequate test for a cable that is going to be used for HDBaseT?

Many integrators will carry a type of LAN tester, these could range from basic wiremappers, right through to 10GbE certifier grade testers. The truth is any type of cable test is going to give some form of indication for the suitability of a signal being able to be transferred across the cable – be it the most basic test of ensuring that the pins have been terminated to their retrospective terminal on the far side of the link; to certifying the cable to a recognised international standard. However, the transmission of packetised data is very different to the modulated HDBaseT data flow.

So, can a 10GbE IP / LAN tester therefore be used to qualify a link that is going to be used for a very different transmission type? Truth is, this will give you the best indication for an 8Gbps signal out of all the LAN test equipment out there, but they are two very different signal types being treated as one – a common misconception because we use the same cable.

TO TEST A CABLE FOR ITS SUITABILITY FOR A HDBASET TRANSMISSION, THE DATA NEEDS TO BE A HDBASET SIGNAL

Once a cable has been run through a property – under floors, behind walls, or above ceilings, it is subject to environmental influences such as EMI or RF interference. The cable may have also been improperly handled during installation without the due care and attention paid to kinks or the bend radius. Other factors such as the number of cables run simultaneously (cable bundling), zip ties being used at multiple points to secure cabling, or improper termination can all have an adverse effect on high-bandwidth data signals. The use of pre-existing cabling within a property could be fraught with risk without the due diligence of qualification, at least before taking out a contract to deliver a video signal from A to B using said cable.

It is fair to say that HDBaseT has been the defacto video distribution method since its inception over 10 years ago, but many still seem to have issues, even if intermittent during commissioning or within the first six months since installation. With Video over IP technology forging forwards, and the capability of being able to distribute visually lossless video over a network, there is a back-up for the times where HDBaseT may not perform flawlessly, but HDBaseT is a proven technology which we know works.

On occasions where we visit a site with an integrator that is having issues with HDBaseT, we first look at the overall infrastructure. Best practises for installation of cabling is usually the first area in which we investigate. In most cases the reports of issues are so random that it is extremely hard to re-create.

We have used the MS-TestPro from MSolutions for a few years now, as the only true test device for HDBaseT that is endorsed by the HDBaseT Alliance. It gives us an x-ray vision to check the key variables for a HDBaseT installation – it also gives us the ability to log performance for up to 24 hours for those intermittent issues that are reported, but not seen.

HDBaseT is such a forgiving technology, designed to get video, audio, control and power across the ‘dusty fields of battle’ – so it copes with many of the issues we throw at it. Unfortunately this flexibility breeds the scenario that many just ‘plug and pray’. Who knows how many installations out there are on the edge of the digital cliff? They work now, but how many will continue to work as the environment changes? It is not about hoping it will work, it is handing over a project knowing that it will continue to perform for many years to come. The MSolutions tester, in our eyes, will confirm this; help to diagnose where there are issues; becoming a bit part of the solution far more effectively than wasted labour or new cabling runs.