We left our Sept. 1 column talking about VGA (video graphics), S-VGA (super video graphics) and RGB cables, variations of multiple coaxes for supporting analog or digital monitors. (S-VGA cables include pairs for other uses.)
If you’re just shipping around VGA signals, such as those used by your computer monitor, you might be tempted to use the same old RGBHV cable you used for those analog video monitors. Most of the time that cable would probably work just fine, especially if the cable is short.
The problem is how the cable is tested. Most RGB cable is tested out to 10 MHz or maybe 25 MHz. VGA and S-VGA applications run much higher sweep frequencies, sometimes out to 400 MHz or more. What are those RGB cables doing at those frequencies?
They weren’t tested that high, so you don’t really know. Maybe they’re fine, maybe not.
Of course, there could be a serious “suck out” at some critical high frequency. This will severely limit the distance such a signal can go down the cable.
So if you are running VGA or S-VGA, use cable that has been tested to an appropriate high frequency. There are multi-coax cables available on the market tested out to 3 GHz, so any sweep frequency below that should be no problem.
There are a number of other similar applications. One is XVGA, extended video graphics, with even higher sweep frequencies. Another is DVI, digital video interface. This is a standard supported by the Digital Display Working Group (www.ddwg.net). This is an open industry group supported by a number of manufacturers such as Intel, Compaq, Fujitsu, Hewlett-Packard, IBM, NEC and Silicon Image.
This cable handles the huge data rate of plasma monitors (1,280 x 1,920 pixels). I’ll be honest; despite many requests to the working group and its members, I’m still not certain what is inside the cable, although a number of knowledgeable people have told me that it is all twisted pairs. If true, this explains why these cables are short, three feet or even less, because twisted pairs are not the best choice at these high data rates and bandwidths.
If you know more about DVI, XVGA or any other emerging standard, let me know. I would love to learn more and share it with the madding crowd.
Now, it’s time to take your milk and cookies and find a comfortable seat. Grandpa Steve is going on one of his extended reveries to tell you the History of Wire and Cable. Our story will take us over several articles.
The History of Wire and Cable, Part 1: Our story starts a long, long time ago – 5,300 years ago, to be precise. This concerns Otzi, the iceman. Unfortunately, he is dead. He has been dead for a very long time. He is the “iceman”dug up in 1991 in the Otzal Alps on the Austrian/Italian border.
Do you know they now believe he was murdered? Researchers found an arrowhead in his shoulder. That probably means he met some bad people in his village over the mountain and was trying to run away. He only got so far until he collapsed. And that was that.
Except for one very interesting thing he was carrying with him, a copper axe. Anyone who plays with copper, as we wire jockeys do, knows that it is a soft metal and makes a very poor axe. But this axe was never used. It is in pristine condition. Metallurgical testing has shown that this copper was 99.7 percent pure, a purity that was only surpassed in the late 1800s. And this gentleman was carrying his axe 5,300 years ago, a full millennium before they had thought the first copper was refined.
So, it occurred to me that there is a good possibility that this axe was a sample, and Otzi was the world’s first copper salesman!
I even sent this suggestion to the researchers working on Otzi. For some reason, I never got a reply.
The First Jewelry Scam, 200 BCE: Fast-forward 3,000 years, to around 200 BCE. On the shores of the Caspian Sea lived a culture called the Parthians. They were an aggressive group, always attacking their neighbors. So it’s a bit unusual, and still a bit controversial, that they were the people who apparently invented wire – that is, wire that carried electricity. Unfortunately, there is no wire left. But they must have had wire to plate jewelry.
To plate something, to deposit a molecular layer of metal over another, requires a couple of things.
First, you need a metal object to be plated. Then you need a piece of the metal you wish to deposit (often gold, as in this case). The object and the plating metal must be attached to two wires and suspended in an electrolyte (grape juice is suspected).
Then you need to attach the wires to a battery. This is the key. In 1938, archaeologist Wilhem Konig found a series of buried earthenware vessels. They contained remnants of a cylinder of copper and, inside that, a rod of iron. Fill this with grape juice – lemon juice or any acid would also work – and you have an efficient 2-volt battery. Koenig found these in rows, as if they were wired in series.
There are many plated objects from the Parthian culture. These are possibly the earliest scam, selling plated object as if they were solid gold. While there is an alternative chemical way to plate objects, using a battery is a lot simpler. And you can’t run a battery without wires. So the Parthians must have had wire.
Now, children, we can only imagine where we would be today if we had not lost this ancient knowledge. Maybe I would be writing this column on Mars, or maybe on a space station, instead of just an airport, where I am at the moment.
This is not the only ancient knowledge that we have lost. In the next few columns, we will look at technology that was resisted or even suppressed. And we will talk about a few instances in which knowledge had to be rethought. Don’t miss a single exciting episode!
Steve Lampen’s latest book “The Audio-Video Cable Installers Pocket Guide” is published by McGraw-Hill. Reach him at [email protected].