Industrial Security
Industrial Ethernet
Data Centers
Broadcast AV
Belden News
Blog Home
Blog Category: Broadcast AV

Posted by: Steve Lampen on August 29, 2013

We've spent a whole month taking about the "digital cliff", about measuring bandwidth, wavelength and critical distance. And we've talked about our "safe distance" table based on the formulas in the HD standard (SMPTE 292M). Use those safe numbers and you don't have to think about anything, you don't have to measure anything. Just put on some connectors and plug it in. If you get failures at these short distance, you have something very wrong, a lot more wrong than a cable a bit too long. Is everything intended for HD? Tested by each manufacturer to AT LEAST 2.25 GHz? (Last time I mentioned how one project was stymied by using analog 75 ohm terminators!)

Read More >>


Comments (0) Post a Comment

Blog Category: Broadcast AV

Posted by: Steve Lampen on August 22, 2013

For the last couple of weeks we've been talking about the "digital cliff" where signals no longer work. Check out the previous installments about bandwidth, wavelength and critical distance (Part 1 and Part 2).

The critical distance is the length at which it is important to know the impedance of the cable, where the cable is now a "transmission line". For signals like professional high-definition video (SMPTE 292M standard), the critical distance is a little over ONE INCH. That simply means that everything is critical, cable connectors, patch panels, patch cords, adaptors.....everything in that passive line between boxes. But that still doesn't tell you where the cliff is.

Read More >>


Comments (0) Post a Comment

Blog Category: Broadcast AV

Posted by: Steve Lampen on August 14, 2013

We've been talking about digital signals and their limitations. The first step is to ascertain the bandwidth of your signal. Our example in Tales of the Cliff - Part 1 was RS-422 which has a bandwidth of 10 MHz.

Once you know the bandwidth, you can calculate the wavelength. 300 million divided by that frequency gives you the wavelength in meters. 300 million divided by 10 million equals 30 meters (about 100 feet). The critical distance is not a full wavelength but a quarter wavelength. (Think about a sine wave. Where is at its maximum effect? A quarter of a wavelength.)

So a quarter of 100 ft. is around 25 feet. And what that means is that, below 25 feet, you can use almost anything to carry RS-422. After 25 feet, it is a "transmission line" and requires that you match the impedance of the source and destination devices with the impedance of the cable. For RS-422, this impedance of the devices is 100 ohms, so the cable will also be 100 ohms. When you put connectors on your RS-422 cable (15-pin sub-D, most commonly) are they 100 ohms? No, they aren't. But it doesn't matter because they are less than 25 feet long. So you can use any connector. But that doesn't tell you the MAXIMUM distance you can go.

Read More >>


Comments (0) Post a Comment

Blog Category: Broadcast AV

Posted by: Steve Lampen on August 08, 2013

I've been having some interesting conversations with customers about the "digital cliff". How to find it....and how to avoid it.

The digital cliff, as you probably already know, is the point where a digital signal cannot be resolved by a receiving chip. Most people assume this is because the cable is too long, in other words the signal has attenuated beyond a point of recovery. But that's only one of a dozen factors that can affect digital signals.

Most people also may assume we're talking about digital video, like HD or 3G. But there's a digital cliff for any digital signal, including for digital audio. There's a cliff for data cables. There's a cliff for RS-232, RS-422, RS-485....and so on.

Read More >>


Comments (0) Post a Comment

Blog Category: Broadcast AV

Posted by: Steve Lampen on July 31, 2013

According to my count, this is Blog Number 50 for me! I have been told that there are thousands of people reading these blogs, which warms the cockles of my heart, but more importantly confirms this is a great forum to share important knowledge to a wider and wider audience.

More than a few people come up to me at speaking engagements or tradeshows and ask, "How can you keep coming up with new ideas for blogs?" I mean, this is wire and cable (at least the blogs I write) and that's not exactly the most exciting thing in the world. Some people are amazed I can talk for a whole hour about wire and cable. (Clearly, they haven't seen me talk, I can go for days!) So where do I get these ideas?

Read More >>


Comments (0) Post a Comment

Blog Category: Broadcast AV

Posted by: Steve Lampen on July 24, 2013

I swear, I can empathize that Belden doesn't make it easy for you to choose a cable for a specific application. A week doesn't go by that someone isn't complaining to me that we have too many choices.

I tell most people that we make "6,000 different kinds of wire and cable". What's the actual number? I don't really know, and I don't know if anyone knows. As the introduction of new technologies speeds up, we bring out more and more new products, so that "total" is a moving target.

It's no wonder that often, when I suggest a cable to a customer, they get angry. You see, this cable may have been in our catalog for 20 years and they didn't know about it. They’ve been struggling with some old cable from the Dark Ages, wishing there was a better way, and it has been sitting there waiting for them. I would be angry too.

Read More >>


Comments (0) Post a Comment

Blog Category: Broadcast AV

Posted by: Steve Lampen on July 17, 2013

I remember hearing a story when I was a student (around the time of the Middle Ages):

A physics professor gave a test question to the class. You have a barometer (a barometer reads air pressure). You're in a 100-storey building. How do you use that barometer to determine the height of the building? The answer is, read the air pressure at the bottom of the building, walk up one floor (measuring the distance of that one floor precisely) and read the pressure on the first floor. Then take the elevator to the roof, and read the pressure there. Then take the difference between the pressure on ground floor and on the roof, and divide that by the difference between the ground floor and the first floor. Then multiply that number by the distance you measured to the first floor.

But I will tell you that this is the WRONG WAY to figure this out. Here is a MUCH EASIER way:

Read More >>


Comments (0) Post a Comment

Blog Category: Broadcast AV

Posted by: Steve Lampen on July 12, 2013

Science fiction author Arthur C. Clarke, who happens to be a friend of mine, once said, "Any sufficiently advanced technology is indistinguishable from magic." Well, welcome to that future. I talked in one of my last blogs about Dick Stoner, our magician at NAB, but truly the cell phone in your pocket, or the tablet in your hand, is greater magic than anything Mr. Stoner could summon up. And some of that magic is in the wire and cable that's used to hook all those things together. Maybe that magic is not quite as obvious, but it's there.

I was talking on the phone the other day to a distributor. He wanted to be sure that what he was stocking were the right products. He wanted to be sure that he wouldn't be left with a bunch of products that were going out of favor or being passed by new technology. Well, as I always do, I started by telling him that my crystal ball was in the shop, and it was pretty foggy looking into it anyway. Nobody can accurately predict the future, at least not the entire future. And as I often tell my audiences, if you DO know what's coming, go see your stock broker! That's how people get rich, by making accurate guesses about where we are going. Even harder is to look at all the new technology which comes out every five minutes and decide which one is the "Next Big Thing".

Read More >>


Comments (0) Post a Comment

Follow Us

Subscribe
Broadcast AV
RSS Feed
Broadcast AV
Email Notifications

Search
Broadcast AV Blog
All Belden Blogs


Stay Informed