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The case for Category 7

Posted by Ralph Parrett on Oct 29, 2014 8:33:00 PM
First thing, full disclosure and the honest truth – there is no such thing as a “Category 7”. However keep reading!

In the USA, the highest official Category rating is 6A (Category 6 Augmented). Category 6A is a 10 Gigabit Ethernet infrastructure cable officially certified to 500 MHz. It can be shielded or unshielded.

In Europe there are two twisted pair ratings above Category 6A, namely ISO 11801 Class F and Class FA. Class F cable is nicknamed “Category 7” in the US. Class FA has been called Category 7E or Category 7A. The true Category 8 standard is in discussion at this time and has not been ratified. All of these cable are shielded, usually with multiple shields.

Why would an AV professional need Category 7 cable? I’ll tell you. HDBaseT® is the reason. Specifically HDBaseT running 4K video. Our industry learns more about HDBaseT every day. One thing we learned pretty early on is do not use unshielded category cables. We all went to foil shielded category cables (F/UTP) to eliminate outside interference. Any cable engineer can tell you that foil shields are great for high frequency signal blocking but not so good at low frequencies like AC power interference, so the industry offered dual shielded category cables in a braided shield + foil shield format (SF/UTP). These worked great for lower resolutions and refresh rates. Liberty’s LLINX-HD is such a cable.

Now introduce 4K video over HDBaseT. The frequency on each pair is crazy and signals are beginning to interfere with each other between the pairs (Crosstalk). HDBaseT does not have error correction like the true HDMI signal has, so the crosstalk introduces errors in the data stream. The best way of eliminating that internal crosstalk and those errors is to shield each pair. Guess what cable already has that construction? You guessed it – Class F or Category 7 cable. The abbreviation for that construction is S/FTP cable. An overall braided shield with at least 65% coverage and each pair foil shielded. The pairs are not isolated from each other but all share one common drain and ground path.

What does Category 7 cable give you? Simply put, a copper highway for extremely high resolutions and frequencies. 4K@30Hz is the maximum HDBaseT resolution right now but you know and we know the 4K@60Hz revision is coming. The Cat7 cable will handle both with aplomb. Cat7 is a bit longer to terminate correctly, each pair requires the shield to be stripped away to put into a plug. You also need specialized RJ45 plugs to terminate this, don’t try to recycle Cat6 connectors onto this cable. A little industry trivia for you - Cat7 cable performance actually exceeds the maximum performance of modular RJ45 plugs. Who knows what connectors we will be putting on cables as bandwidth requirements continue to push the boundaries?

Few LAN based Category 7 cable have the striping on the white conductors, called the tip conductors. Liberty knows our product is meant for the Pro A/V market and we ensure the appropriate striping and/ or banding is on our tip conductors.

Liberty’s Category 7 cables are:

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