HDMI Distribution Technologies
HDMI is pretty much standard for TVs, projectors and sources these days. When composite video was the de-facto standard distributing this sort of signal was very easy – good quality, well-screened co-axial cable allowed the signal to be transmitted over fairly long distances without too much loss of quality – although the quality of the original signal was not very good.
HDMI provides much better quality video and audio but is much harder to distribute. Not only is the accepted maximum length for a normal HDMI cable only about 15m but the connector on the end if so big that routing it around a property is almost impossible in any sort of quantity.
Using an alternative cable
The obvious choice is to use a different cable and then convert it at each end to HDMI. One option is component video which uses three separate co-axial cables to transmit a HD video signal. However there is no audio with this so a separate cable is required for digital audio and if you want any form of control (i.e. infra-red repeater) you may need another cable. Co-axial cable, whilst cheap, is fairly bulky and stiff which can make installation difficult.
The other option is twisted-pair cable like Cat5e, Cat6 or Cat7 cable (also known as CatX cable). This is a lot less bulky than co-axial and only one or two cables are required rather than four or five. Not only does this make installation cheaper but it also makes it quicker and less destructive.
Standard HDMI Distribution Baluns
A balun is a device that converts from one format to another. There are plenty of baluns on the market that convert HDMI to CatX cable and back again. These use one or two cables depending on the length of the run, the HDMI standard to be transmitted and other services that are required (e.g. infra-red repeater, data connection etc.).
These baluns are perfectly serviceable but have their limitations. The usually maximum cable length is 45m and they only support HDMI v1.3 which means no data connection or support for the latest specifications. In addition if you want a infra-red repeater facility you will need a twin CatX system.
HDBaseT – The Next Generation of HDMI Distribution Baluns
Formed in 2010 HDBaseT is an organisation that has developed a much improved way of transmitting an uncompressed HDMI signal over CatX cable. Using a similar technology to normal data networking it can support the latest HDMI standards and provides infra-red repeater facility and data connection as well.
The HDBaseT technology can support cable lengths up to 100m and is much more robust technology than the standard baluns. In fact HDBaseT can support up to 800m cable lengths with repeaters every 100m!
The latest developments to HDBaseT include being able to provide 100W of power down the cable so that not only can the receiving balun be line-powered (meaning no bulky plug and transformer at the TV) but it can also potentially power the TV itself! Obviously this only works with compatible TVs with a 12Vdc input but this could revolutionise HDMI distribution.