Are you being coaxed into using the wrong medium for broadband?

Wouldn’t it be great if hospital rooms were cabled for high-speed Internet access and interactive television? We could use a handheld remote or wireless keyboard to access the network through the hospital room’s TV.

Apr 1st, 2005

Wouldn’t it be great if hospital rooms were cabled for high-speed Internet access and interactive television? We could use a handheld remote or wireless keyboard to access the network through the hospital room’s TV. If your room is “hot,” you can watch personalized educational materials on your condition, and ask questions of your doctor or the on-duty nurses.

Is this new? No. All this can be delivered over the same system that lets you check your billing statement, watch movies on demand, and play video games in hotels.

And all the hotels that I have examined lately are connected via coaxial cabling.

CATV cabling for hospitals

Since my January column on the use of coaxial in hospitals for CATV, I have received a lot of feedback:

Phone calls from vice presidents of companies selling proprietary hardware systems that are required to make broadband over unshielded twisted-pair cabling function.

• Bundles of slick marketing materials touting the virtues of the new way to deliver broadband signals, in which ease of installation and maintenance are repeatedly cited, but include no mention of the guy who is paying for the equipment and the “better-than-Category-6-cabling” necessary to get coax-like results.

• Messages from those selling UTP cabling, asking what could I have possibly been thinking, recommending coax as the medium for TV.

And from those who agreed with my keep-it-simple approach: “way to go.”

Begin with the basics

Radio frequency waves, which deliver cell phone calls, television, and radio broadcasts, are energy-transmitted through space. This energy consists of the alternating waves of electric and magnetic fields, thus the term “electromagnetic energy.”

Electromagnetic energy only manifests itself when it interacts with matter. The type of material with which electromagnetic energy interacts is dependent upon the frequency.

X-rays and gamma rays are at the short end of the spectrum, visible light sits close to the middle, and radio waves are at the long end of the spectrum:

• X-rays and gamma rays have wavelengths so short they can squeeze into atoms to ionize and upset them.

Light has wavelengths about a half-micron.

Microwaves, with wavelengths in the range of 1-mm, can heat water-containing materials by causing the water molecules to vibrate.

• Radio waves, of the meter-or-so length, are used for public communications broadcasts.

• Very long wavelength electromagnetic energy is used by the Navy to communicate with submarines under hundreds of feet of seawater and halfway around the world.

When electromagnetic radiation in the broadcast range contacts a metallic object, it will cause current to flow in that object. The current will adopt the frequency of the electromagnetic wave that strikes it. If the metallic object is the antenna of a radio or cell phone, attached to circuitry appropriate to decode the signal, you have communications.

But any metallic object can generate a current if struck by electromagnetic waves. The amount of current depends upon the strength of the electromagnetic field, and the exact geometry of the metallic object. This is how communications antennae are “tuned” to the exact frequencies.

Electromagnetic radiation is all around us. Television, radio, cellular, and other broadcasting equipment bathe us all in a pool of electromagnetic waves. It is very difficult to exclude this electromagnetic pollution.

The Food and Drug Administration (FDA) and Federal Communications Commission (FCC) have known for years that electromagnetic radiation could interfere with medical equipment operation. But having an electromagnetic radiation source within feet of a piece of sensitive medical equipment is very different from being 20 miles away from a radio tower.

As with all electromagnetic radiation, the strength of the field decreases with the square of the distance from its source. Translation: the field strength 1 meter from a transmitter is 4x as strong as the strength, only another meter away. This may put the electromagnetic shielding of medical equipment to a tougher test.

The FCC has authority over all forms of equipment that can transmit electromagnetic energy. The FDA has authority over all forms of medical equipment (both disposable and durable), medications, and associated delivery systems or devices.

The FDA has never banned any communications equipment, and is prohibited from doing so by its charter. The FDA has, however, placed pre-marked requirements on medical equipment (i.e., shielding requirements).

The FCC has never banned transmitters of any type from hospitals, provided that the equipment falls into compliance with FCC radiation-flux-levels.

Remember the old Category 5 debate of “why do we need a 100-MHz cable when you cannot transmit above 30 MHz without violating FCC regulations?” Back then, the cable guys alleged, “We are not required to meet FCC because our product is not a transmitter. Compliance is the equipment guys’ problem.”

But if the cable is not shielded and not perfectly balanced, leakage will occur. And we are not talking about 100 MHz anymore. Broadband cable television has signal levels up to about 1,500 MHz, and standard satellite to about 2,250 MHz. High-definition satellite will be in the range of 2,600 to 2,800 MHz.

While I do understand some of the basics of broadband distribution, I am by no means a radio-frequency engineer. So, I decided to rely on a few folks who are.

Paul Kish, director of IBDN Systems and Standards with Belden CDT, has published several white papers, including “Broadband Video over Twisted Pair Cabling” and “Broadband Video over Category 6 UTP Cabling,” in which he demonstrates why you should install a better-than-Category 6 cable to support broadband video. Why? Because with Category 5e and Category 6, you get a degradation of picture quality. (To view these white papers, visit www.nordx.com/public/htmen/WhitePapersUSINT.htm)

TIA TR-42 has established a study group to investigate the need for coaxial cabling within residential cabling and data centers. John Pryma, director of structured cable at Honeywell Cable Products, will chair the study group, which will also investigate applications in commercial buildings and health centers.

One of the most demanding applications for which we currently design cabling systems is broadband video. Coaxial cable (RG-6 or RG-11) is commonly used for these applications. I would be remiss if I did not also mention that high-performance twisted-pair cabling can also support broadband video. But why you would want to still escapes me.

Everyone is entitled to his or her own opinion. I have stated mine. Now you will have to decide for yourself and your clients what will work best for your particular project.


DONNA BALLAST is BICSI’s standards representative, and a BICSI registered communications distribution designer (RCDD). Send your questions to Donna via e-mail: dballast@swbell.net

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