HDMI variables: What to bear in mind

When considering HDMI cable lengths and whether you will be able to transmit a signal successfully over a longer length, it is important to remember that when HDMI was originally developed the maximum cable run was envisaged to be no more than 5 meters. In 2008, with the finalization of HDMI, 1.3 using Category 2 specification cables, this length was increased to 15 meters. There are a number of variable factors that can come into play to determine if the cable run you use to connect up your devices will be successful. By understanding what these are it will be easier for you to troubleshoot any problems you may encounter.

Each HDMI device produces a signal strength and this can vary, not only manufacturer by manufacturer, but also from one device to another from the same manufacturer. You may find that the 15 meter cable that you have works fine between two devices, but changing one of them for a third device means that the content doesn’t display itself. The culprit is neither the cable nor the device but the combination of the pair of them. The answer is to investigate which type of HDMI is the best for the two devices in combination and use the HDMI cable that is suitable. It may be a frustrating aspect of HDMI but that is, if you like, “the nature of the beast.”

Fortunately, manufacturers have not been deaf to the voices of those in difficulty. In order to combat these problems newer HDMI devices come with cable EQ (equalization) circuits built into their devices. EQ acts to correct the filter effects found in longer cables and allows the device to correctly interpret the input it is being sent. With the release of HDMI 1.3, the troublesome problem of overshoot was dealt with and eliminated, thereby enabling the use of pre-emphasis coming from transmitting devices. With these two problems effectively solved, the use of longer cables for HDMI transmission became far more of a reality.

If you talk to a computer cabling installer they will tell you that cable quality is the key to successful data traffic transport. Exactly the same applies with HDMI cables. Always keep in mind that in the world of HDMI there are two categories of cable; Category 1 and Category 2. The HDMI authorities recommend that Category 1 is suitable for short cable runs of up to 5 meters, whereas longer cable runs must use Category 2 cables. There is some confusion when you are trying to find the right Category 2 cable for longer runs, as to whether the Category 2 cable you are considering will do the job. Always check the length with the vendor.

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