Digging Further Into the Mystery
BY: Shane Weaver
In this article, we’ll be discussing the difference between Cat6 and Cat6a cables. It may sound like a single lowercase letter is all that sets the two apart, but that one little letter stands for augmented, and represents a world of difference. In the previous article we mentioned that Cat6 is quickly becoming the go-to cable standard for network installers, but just when you thought you didn’t have to worry about technology becoming obsolete, Cat6a comes along and makes Cat6 look like the guy who showed up to the fancy red carpet event in last year’s Ferrari. Basically, Cat6a outdoes its predecessor in performance, crosstalk prevention, and even size. But is it worth it to upgrade? CableOrganizer.com gives you the rundown on what makes these two sound-alike cables so different from each other.
Let’s start with the basics: Cat6 and Cat6a were designed for Gigabit Ethernet and other standard network protocols, so they can both handle 10BASE-T, 100BASE-TX, 1000BASE-TX, and 10GBASE-T. The differences don’t become clear until you start looking at speed and distance.Cat6 cable is rated for 250 MHz, so it has a reduced maximum length (37-55 meters) when used for 10GBASE-T applications. Cat6a doubles that capability by performing at up to 500 MHz, which allows 10GBASE-T to be run over longer distances of up to 100 meters. Both Cat6 and Cat6a are backward-compatible with Cat3, Cat5, and Cat5e, but if you’re still using Cat3, maybe to connect your Morse code telegraph machine or whatever, I question how you’re even reading an article on this new-fangled thing called the internet. Get with the times!
Since we’ve been talking performance, we can’t neglect to mention crosstalk. Crosstalk, for those unaware, is the phenomenon in which a signal from one channel or circuit interferes with another channel or circuit’s signal. You don’t want that. And thanks mainly to better insulation, signal degradation from near-end crosstalk (NEXT), power sum NEXT (PS-NEXT) and attenuation is already far lower in Category 6 cable than it was in earlier versions like Cat5 and Cat5e. Cat6a reduces this to an even lower level. In the realm of crosstalk, the most significant improvement of Cat6a over Cat6 relates specifically to alien crosstalk (AXT), which sounds awesome, but just refers to cables interfering with the signals of other cables in close proximity. This tends to be significant in Category 6 cables exposed to high frequencies, but quite low in Cat6a.
Size and Other Physical Properties
Back when the first wave of Category 6a cable came out in 2008, it was 50% larger than the average Cat6. Since then, many manufacturers have managed to slim down their Cat6a cables by up to 10%, but even with the slight loss of bulk, it’s still the Big Bertha of cables. It also places an unprecedented emphasis on twist; while Cat6 combines tight pair twists with extra insulation to reduce crosstalk, Cat6a takes things even further by additionally twisting each pair around a flexible (and also twisted) central plastic support. It’s like a DNA helix and a pretzel had a baby and that baby was a Twizzler…seriously, just so many twists.
Seeing as how demands for greater bandwidth and less attenuation only increase over time, the general consensus among installers is that Cat6a is smart move toward the future, and its size and weight issues are more than made up for by its overall speed and resistance to crosstalk. There are just a few things to remember and plan for when you’re working with Cat6a:
- It’s heavy. With the added size of Cat6a comes a significant increase in weight, which affects how many cables you’ll be able to fit into a cable tray, as well as where you can place them. Cable tray capacity is drastically reduced when you’re using Cat6a cable, because it takes up way more space. That means bigger cable trays and conduit, as well as a restriction on bundle size – it’s recommended that you bundle no more than 50 Cat6a cables at a time. In-tray placement is also key: always make sure to place Cat6a at the bottom of the basket, so that it won’t crush smaller-diameter cables with its massive girth.
- It Requires a Bigger Bend Radius There may be a few exceptions, but as a general rule of thumb, the larger a cable’s diameter is, the larger its bend radius needs to be. The wider bend radius of Cat6a cable requires more room than the tighter bend radii of thinner network cables, so it’s important to allow extra space anywhere your Cat6a cables may need to bend, be that behind a wall jack, or at the end of a cable tray run.
- It Doesn’t Like Zip Ties When you use standard cable ties on any type of network cable, it pays to be gentle, because there’s always the risk of attenuation due to over-tightening. However, Cat6a cable is exceptionally prone to crushing, so it’s best to use wider, looser hook-and-loop cable straps in place of the plastic zip ties that you’d normally reach for. Despite having a little bit of a weight problem, you still have to treat it like a fragile flower. It’s like a woman in a Botero painting: hefty but delicate.
- It’s Packaged Differently Than Other Category Cables A lot of installers have grown accustomed to dispensing Cat5 and Cat6 cable from convenient pull-box packages, but Cat6a is most widely available on reels. This isn’t a deterrent to most people, but it does mean that you’ll have to plan accordingly, and keep a strong, appropriately-sized stand or cart on hand for storage, transport and dispensing.
- It Needs More Testing Since it’s capable of speeds up to 500 MHz and alien crosstalk begins at only 350 MHz, Cat6a needs more testing than earlier categories of network cabling. When quoting a job requiring Cat6a cable, be sure to budget extra time for the following tests: alien attenuation crosstalk ratio far-end (AACRF), alien far-end crosstalk (AFEXT), alien near-end crosstalk (ANEXT), power sum alien attenuation crosstalk ratio far-end (PSAACRF), power sum alien far-end crosstalk (PSAFEXT), and power sum alien near-end crosstalk (PSANEXT). I’ve been assured that those are all real things and not just made-up acronyms, so you’ll probably want to plan accordingly.
So there you have it. Cat6a is bulkier and heavier than Cat6, and it needs to be treated more carefully, but it allows you to cover longer distances and greatly reduces all that nasty crosstalk. If these benefits outweigh the drawbacks (pun intended) for your applications, then you might want to invest in that little “a”. It makes a big difference.