Virtually all TV broadcasters around the world have gone digital. Even Hollywood has converted from film to digital images. While some of these cameras record the data on hard drives or SSD (solid-state drives), at some point you’re going to send this data, those digital images, from Point A to Point B. If you want to carry the hard drive or SSD from place to place, that’s fine (so-called “sneaker net”) but it is time-consuming and inefficient. Why not put that signal on a cable to move it from place to place? That’s what most broadcasters do. And, while you could do this on fiber, converting from electrons to photons and back again at the other end, the economical and simple way is still over copper cable, most commonly coax cable.
The photo to the right is Belden 1694A, the world’s most popular video cable. It’s a good compromise between size, distance, and cost. It is easy to put on connectors, especially the one-piece compression connectors that Belden now offers. (Our current record is two connectors in 33 seconds.) And these connectors, and the 1694A cable, can carry virtually any video signal you might wish to use including analog, 4×3 digital (SD-SDI), high definition (HD-SDI) and even 3gig (1080p/50 or 1080p/60).
The only thing you have to consider is how far the cable can go. Here’s a chart showing the recommended distance for 1694A and all of our other digital cables. Read more
One of the greatest challenges presented by the arrival of 4K video is in the ability of this signal to be carried by a single copper coaxial cable, commonly called “single link”.
Proposed Change in Distance Calculations
It is most important for a broadcaster to know how far he can transmit a signal over a single coax cable. In recent years Belden has proven that the recommended SMPTE distance calculation for HD signals can be outperformed. The original distance formula, -20 dB at ½ clock, was a reasonable “safe” value for 1990 and the technology then available. However, we believe that more than 20 years of improvements in chip design and active equipment has enabled us to surpass this calculation. Therefore, we think that a new formula, -40 dB at ½ clock, is an appropriate “safe” distance. And in the ‘real world’, Belden can go considerably further than that.
Let’s have a look at the green squares in the chart: Belden’s 1694A for example can run a minimum 113 meter with HD. With 2K signals 1694A runs a minimum of 78 meters, or 35 meters less when compared to HD. In general, all these lengths can be improved on by using our HD coaxial cables and BNC connectors. See for example the 140 meter at HD with 1694A.
If you remember that the bandwidth of 4K is 8 times HD and 4 times 2K, everyone would expect the minimum distance of a 4K signal to be less than HD or 2K. But look at the red squares. The chart clearly shows how Belden’s 1694A runs 106 meter with QuadFull-HD on a single-link! In other words: 28 meters further than 2K.
I was talking to a friend of Belden’s at a recent trade show. We were discussing using Category cable for audio, something we have discussed at great length in this blog. “I never use that cable for audio,” said the customer.
“Why not?” I asked.
“Well, all the install Cat 5e or 6 or 6a is solid conductor,” he replied. “And we all know that solid conductors break.”
He was especially insistent that those solid conductors, when soldered into an XLR, often break. This is called ‘work hardening’. Do you believe that? If you do, it probably means that you’ve been using some very cheap cable, because wires that break are not annealed correctly. One of the things you get with good quality cable and good quality manufacturing is annealing. Annealing is a process where the conductor is put into a hot oven to let the molecules come in contact with each other after the drawing process (big wire drawn into smaller wire), but not hot enough to melt the copper. Cheaply made cable sometimes rushes this process or does not anneal at all, creating a brittle wire that will break with just a few flexes. Everyone remembers bell wire from the hardware store. Probably not annealed at all.
Belden’s solid wire, with high-quality annealing, is a different story. I remember when we first came out with MediaTwist (Belden 1872A). This is four pairs of solid wires. At tradeshows, we ran a contest to see if attendees could get the signal running down the cable to stop in one minute. The winner would receive a CD player (or something like that). Attendees became very frustrated because they could not break this cable in one minute no matter how they mangled or flexed the cable. How many flexes was that? Probably a few hundred. I remember some people concentrated on one place on the cable and flexed it as many times as they could. No luck. Some very strong guy finally managed to step on the cable and pull it so hard he broke the cable. The pull strength of this cable is 45 lbs., which means the breaking strength is around 112 lbs. One other person tried to bite it. So we changed future shows to “hands only” (no feet, no teeth).
So how many flexes? When we test for flex-life, we do it in something called a C-track tester, which is the kind of bending you would see in a factory. With this testing equipment, cable will last around 2,000 flexes. In the hands of crazy customers? Hard to say. But if you’re worried about solid conductors breaking, it just depends on how much you paid for the stuff.