By employing some of the fundamental best practices for HDBaseT, installers can simplify installation, testing and future maintenance, in order to provide a better customer experience.
Dana Zelitzki *
Every audiovisual installation includes numerous devices, often of different brands. Its configuration depends on the application, the client's needs and the available resources. A good installer will do what is necessary to ensure a smooth installation and, most importantly, a smooth operation. Let's start with the basics: the wiring.
Choose the right wiring
Proper wiring is the basis of any professional AV installation. There are several wiring options on the market that can be used with HDBaseT: cables of different categories (5e, 6, 7 ...), unshielded or shielded, fiber. The cable you choose will depend on the details of each installation.
The minimum cable requirement for HDBaseT is Cat5e without shielding (which is one of the cable configurations used during the regulatory compliance test of the equipment, necessary to obtain an HDBaseT certification). Cat - LAN cables - are used for Ethernet connection, any recommended practice on Ethernet installation also applies here. Cat cables have several advantages over other cables, such as HDMI cables: they can be terminated at the installation site, can extend over longer distances, are more flexible and cost less.
Cable performance is defined based on the quality of the cable, the distance of the connection, the routing of the cable and the expected video resolution. A rule of thumb is that the higher the resolution, the better the cable should be. The same applies for distance. It is very likely that the wiring infrastructure of any project will last a long time, therefore, it should last longer than any other component of the system and, consequently, when choosing the cable, new applications, additional users and users must be taken into account. the possible expansions of the entire system.
Shielded cables are better to prevent the noise produced by electromagnetic interference from reducing the quality of the signal in the cable, as well as to reduce the noise emitted by the cable. However, when working with shielded cable, you must consider the type of power supply that is connected to the equipment. The two-pin power supplies have floating ground connections that differ in grounding levels, and if you connect the shielding of the wire at both ends, this potential difference will cause the current to flow in the shield, which reduces the general performance
The solution when using floating power supplies at each end of the link is to connect the shield to only one side of the link. This will prevent the flow of current in the cable shield, while offering some immunity to noise. Similarly, if you use a floating power supply at one end of the link and a grounding chassis at the other end, just connect the side shield with the grounding chassis. When using a PoH / PoE power scheme (power via HDBaseT / via Ethernet), the shield must be connected at both ends for maximum protection.
Try not to untwist or bundle cables excessively
Another way to reduce electromagnetic interference from external sources is to pay attention to the termination of the cable. It is important not to untwist more than 1.5 cm (and preferably less than 1 cm) from the termination point, and remove the least possible amount of cover.
LAN cables are very resistant. However, any improper handling, such as too tight flanges, pinching or stapling, can damage the cable, compromising its performance or even preventing the transmission of the signal. The grouping of cables is important when planning how to route from matrices / switches. However, when using Cat5e or Cat6 cables, it is important to follow some guidelines for the first 20 meters of the HDBaseT transmitter equipment:
• Do not use organizers or color markings on the cables, try to leave those first 20 meters a bit disordered as this reduces the noise that can be induced in the adjacent cables.
• Always keep the HDBaseT cables and the power cables of the equipment separate. Be sure to use suitable cable support systems when there are too many cables, such as trays, brackets or J-hooks.
• Cable ties introduce pressure points in the cables that produce inconsistencies in the properties of the cable. This in turn causes signal reflections on the cables that affect their performance. If you use flanges, keep them loose.
• Do not clog the conduits that carry the cable bundles. It is advisable not to exceed the 40% fill density, but never exceed local regulations. If it is necessary to pull the cables, be sure not to pull too hard because that can also cause the pairs to de-stress and decrease their performance.
• Do not over bend the cables. Another important issue for the integrity of the cable is the radius of curvature. The radius of curvature is the inside curve of the cable during and after installation. It is best to maintain a minimum radius of curvature of at least four times the diameter of the cable, which means that the cable should not bend below that radius, so as not to damage it and compromise the transmission of the signal. Excess curvature can loosen or modify the braid of the cable and increase the susceptibility to external noise and near-mid-range within the cable.
Termination and & interconnection cables
One of the advantages of using LAN cables with HDBaseT technology is that they are easy to set up at the installation site. This means that there is no need to pre-measure the cables or prepare in advance all the assembly for the installation, thanks to which time and money is saved. Be sure to use the proper equipment for the set-up, such as wire strippers, electrician's scissors and pliers. Also, make sure that both ends of the cable are connected according to the same scheme, either T568A or T568B.
If possible, avoid interconnecting cables or cables completely, as each connection has transmission losses. If absolutely necessary, be sure to use less than two cables per run and keep each less than five meters from the end. And remember, shielded cables must be connected with shielded connectors to maintain the overall integrity of the cable shield.
Recommended cables and certification of feeding through HDBaseT cable
The recommended HDBaseT cables are cables that have been tested in a test center recognized by the Alliance and that have met the requirements established by the HDBaseT Alliance organization. The objective of the Alliance with the recommended cables program is to help installers, integrators and consumers to select LAN cables that meet the current requirements of the Telecommunications Industry Association (TIA) and consequently, ensure its optimal performance with HDBaseT devices.
In addition, HDBaseT Alliance partnered with UL LLC, a cable testing center recognized by the HDBaseT Alliance (which is also a global security science company), to test the cables recommended by HDBaseT and verify their performance when grouped into beams , as well as its compliance with the security requirements in the transmission of power 100W.
The certification program for power cables through HDBaseT (PoH) tests and verifies the cables to ensure they meet the highest safety and performance standards in the industry. Given the increasing complexity of audiovisual installations and the increasingly widespread use of power through HDBaseT (PoH) equipment, the PoH Cable Certification Program offers standardization and consistency, in order to guarantee high performance, regardless of the cable bundles.
PoH generates heat inside the cables, which must dissipate, and obviously this is difficult when the cables are grouped. In addition, because the copper wires get hot, the characteristics of the wire change and this has a detrimental effect on insertion loss. The UL verification program ensures that the performance of HDBaseT, as well as the cable itself, is not affected by this heat buildup.
Developing a set of rules and procedures when installing any AV configuration is important to ensure quality and good performance, and simplifies maintenance and future updates. A final measure that must be taken into account for cable management is to document and label all the wiring components (for example, the connectors), to facilitate any future upgrade or expansion. The installation diagrams are indispensable. Be sure to remove the abandoned cables to avoid accidents.
In the next article, we will talk about more best practices for HDBaseT installations.
* Dana Zelitzki is president of the Marketing Committee of the HDBaseT Alliance.