The HDMI cables are the most widely used when it comes to connecting HD equipment and they are the ones that can transmit audio and video digitally over a single cable. Despite their many advantages, they are not foolproof and if you want to link a source to an HDTV or another display over a distance of 15 meters or more, you can run into problems. The HDMI licensing does specify the maximum length of the HDMI cables, but most writers believe that a cable longer than 10 meters could cause problems and since the HDMI cables carry digital signal, the consumer will see this problem as no signal at all.
In order to connect an HDMI-enabled source such as a Blue-ray player of HD DVD player to an HDTV with an HDMI cable, where the source and the display are more than 15 meters part, you are going to need an HDMI extender. The HDMI extenders (also called amplifiers, equalizers and repeaters) use the 5V DC from the HDMI source or external power source and allow for chaining two or more HDMI cables together. There are cables with built-in boosters too, which cables could work even if they are 30 meters long and then there are Category 5 and 6-based extenders, which work in up to 250 meters distance. For commercial or private applications, where the distance is greater than 250 meters, optical-fiber based extender could be used since they could transmit the signal over 300 meters distance.
In most cases, when you try to use a very long HDMI cable, you will either see no picture at all and hear no sound or you will have pixelization. Luckily, there are quite a few companies, which offer HDMI extenders and they are not overly expensive either. These extenders cost anywhere from a few to a few hundred pounds and could help you with your home theater setup – keep in mind that the extenders still need to be powered up (higher electricity bill) and they have to be HDCP compliant if you are intending to transmit and watch HDCP content. On the other hand, they are very easy to install and in most cases, all you have to do is run one HDMI cable from the source to the extender, plug it in, then run another HDMI cable from the extender to the HDTV, turn the source the TV, and the extender on, and you are good to go!