Running Long Cable Lengths
Like all HDMI-enabled components, cables must be tested to meet the Compliance Test Standards set by the HDMI Licensing Administrator, Inc. Cables must successfully pass a signal of a certain strength (Standard cable must deliver a signal of 17Mhz; High Speed must deliver a signal of 340Mhz) to pass compliance.
The HDMI specification does not dictate cable length requirements. Different cables can successfully send HDMI signals various distances, depending on the quality of the design and construction. As well, HDMI compliance testing assumes “worst case” scenarios – testing with components who have minimally performing HDMI electronics. That is why you may see cables in the market that claim to successfully pass an HDMI signal at very long lengths. This may be true using certain quality CE components on each end, but may not work in every case. It is best to test entire systems before installing.
Active Cables & Boosters
Using active electronics to boost and clean up the signal can effectively double the range of a standard twisted-copper HDMI cable. Cable runs of up to 30 meters are the norm for this type of solution, which may be deployed as either a standalone signal management device, i.e., a repeater or booster box, or incorporated into the manufacture of the cable itself. Boxes are available in many configurations, usually incorporating both booster and equalization functions, and may also serve as repeaters or switchers. Active cables, on the other hand, embed the signal-enhancement electronics in the cable itself, with chips embedded in the connector housings. They are unidirectional, using different modules at the transmit and receive ends of the cable. All the technologies in this category require external power.
Beware products that draw power from the +5V power line. Although these may work in certain applications, different components draw varying amount of power from that line to communicate with each other. A cable that draws power from the HDMI cable may fail when components and the active components in the cable or external booster are all drawing from the same source.
HDMI over Cat 5/6
Runs of up to 50 meters can be achieved by sending the HDMI signal over a run of Cat 5/6 networking cable, using special adapters designed for this purpose. As with the active cable solutions discussed above, they incorporate booster and equalization electronics at each end of the path, and require external power. Because of its tighter manufacturing tolerances, Cat 6 cable is generally preferred over Cat 5 in these applications.
HDMI over coax
This technique consists of a transmitter / receiver pair that convert HDMI signals for transmission over RGBHV or RGBS coaxial cables. The benefits of this solution are long reach (up to 300 feet at 1080p resolutions), the ability to easily terminate connections in the field, and an easy upgrade path for existing RGBHV or RGBS coaxial installations in office or commercial installations.
HDMI over Fiber
The longest HDMI cable runs seen to date have been achieved using fiber-optic cable, which is far less susceptible to attenuation and interference than copper. Electrically it is similar to an active cable or Cat 5/6 solution, the principal difference being the higher-quality optical cabling between the transmit and receive connectors. HDMI over fiber is a highly robust solution, effective in cable runs up to 100 meters or more.