The wikipedia article on HDMI talks about cable lengths. They suggest a standard cable may be limited to about 13 meters (50 feet) unless a pair of extender boxes are used:
An HDMI cable is composed of four shielded twisted pairs, with impedance of the order of 100 Ω (±15%), plus seven separate conductors. HDMI cables with Ethernet differ in that three of the separate conductors instead form an additional shielded twisted pair (with the CEC/DDC ground as a shield).[51](§HEAC-2.9)
Although no maximum length for an HDMI cable is specified, signal attenuation (dependent on the cable's construction quality and conducting materials) limits usable lengths in practice[68][69] and certification is difficult to achieve for lengths beyond 13 m.[70] HDMI 1.3 defines two cable categories: Category 1-certified cables, which have been tested at 74.5 MHz (which would include resolutions such as 720p60 and 1080i60), and Category 2-certified cables, which have been tested at 340 MHz (which would include resolutions such as 1080p60 and 4K30).[6](§4.2.6)[62][71]Category 1 HDMI cables are marketed as "Standard" and Category 2 HDMI cables as "High Speed".[4] This labeling guideline for HDMI cables went into effect on October 17, 2008.[72][73] Category 1 and 2 cables can either meet the required parameter specifications for interpair skew, far-end crosstalk, attenuation and differential impedance, or they can meet the required nonequalized/equalized eye diagram requirements.[6](§4.2.6) A cable of about 5 meters (16 feet) can be manufactured to Category 1 specifications easily and inexpensively by using 28 AWG (0.081 mm²) conductors.[68] With better quality construction and materials, including 24 AWG (0.205 mm²) conductors, an HDMI cable can reach lengths of up to 15 meters (49 feet).[68] Many HDMI cables under 5 meters of length that were made before the HDMI 1.3 specification can work as Category 2 cables, but only Category 2-tested cables are guaranteed to work for Category 2 purposes.[74]
As of the HDMI 1.4 specification, the following cable types are defined for HDMI in general:[75][76]
- Standard HDMI Cable – up to 1080i and 720p
- Standard HDMI Cable with Ethernet
- Standard Automotive HDMI Cable
- High Speed HDMI Cable – 1080p, 4K 30Hz, 3D and deep color
- High Speed HDMI Cable with Ethernet
A new certification program was introduced in October 2015 to certify that cables work at the 18 Gbit/s maximum bandwidth of the HDMI 2.0 specification.[77]In addition to expanding the set of cable testing requirements, the certification program introduces an EMI test to ensure cables minimize interference with wireless signals. These cables are marked with an anti-counterfeiting authentication label and are defined as:[78]
- Premium High Speed HDMI Cable
- Premium High Speed HDMI Cable with Ethernet
In conjunction with the HDMI 2.1 specification, a third category of cable was announced on January 4, 2017, called "48G".[79] Also known as Category 3 HDMI or "Ultra High Speed" HDMI, the cable is designed to support the 48Gbit/s bandwidth of HDMI 2.1, supporting 4K, 5K, 8K and 10K at 120Hz.[80] The cable is backwards compatible with the earlier HDMI devices, using existing HDMI type A, C and D connectors, and includes HDMI Ethernet.
Ultra High Speed HDMI Cable (48G Cable) – 4K, 5K, 8K and 10K at 120Hz
.
An HDMI extender is a single device (or pair of devices) powered with an external power source or with the 5V DC from the HDMI source.[81][82][83] Long cables can cause instability of HDCP and blinking on the screen, due to the weakened DDC signal that HDCP requires. HDCP DDC signals must be multiplexed with TMDS video signals to comply with HDCP requirements for HDMI extenders based on a single Category 5/Category 6 cable.[84][85] Several companies offer amplifiers, equalizers and repeaters that can string several standard HDMI cables together. Active HDMI cables use electronics within the cable to boost the signal and allow for HDMI cables of up to 30 meters (98 feet);[81] those based on HDBaseT can extend to 100 meters; HDMI extenders that are based on dual Category 5/Category 6 cable can extend HDMI to 250 meters (820 feet); while HDMI extenders based on optical fiber can extend HDMI to 300 meters (980 feet).[82][83]
from:
https://en.wikipedia.org/wiki/HDMI
