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Microwave radio link for Pakistan's power grid system.

Microwave Radio Link for Pakistan's Power Grid System

When using the telephone we tend to think of telephone calls as being transmitted over wires after all, we see them leaving our houses and heading for the nearest telegraph pole - and we probably try not to think too hard about how large numbers of conversations are concentrated and transmitted over long distances. Via huge bundles of wires, perhaps? Of course, the more technically aware know that international telephone calls are "multiplexed" and transmitted via satellite and that intercontinental cables are capable of carrying high volume traffic.

These days the top of the highest hill in any district is likely to be the site of a concrete mast or steel tower or mast hung with parabolic or "dish" antennas, all pointing in different directions. These antennas send and receive microwave signals, i.e. radio waves with frequencies of between 2 and 50 GHZ (thousand million cycles per second). In fact, every single antenna is aimed at a similar one on another tower or mast in the far distance, perhaps as much as 40 or 50 miles away.

One feature that makes microwave links attractive for carrying telephone traffic and television is the fact that microwave radio signals travel in line of sight from point to point. As a result, if the beams are properly aligned, the same frequencies can be used over and over again without interference, as long as the signals are sent in different directions. On the other hand, information can also be disseminated throughout a whole district by using omnidirectional aerials, once again as long as all the receivers (e.g. individual TV sets or local telephone exchanges) are in line of sight of the transmitter. A single high-capacity microwave channel (i.e. one frequency can carry more than 1700 telephone conversations simultaneously, so capacity is seldom a problem.

Microwave systems are also relatively inexpensive to install, as ground does not have to be bought or prepared for poles or cable trenches; in many cases, the relay stations and their masts can be integrated into existing plant owned by the agency or utility that operates the microwave link. Once the backbone of the system has been installed, adding local links lets it reach more users as needs increase and financial resources become available. Even temporary link can rapidly be set up if emergency communications are needed or wherever a short-term need is identified.

Most of the equipment for the network supplied to Pakistan was designed and manufactured by EB NERA, Norway's national supplier of microwave radio links. Over the past 40 years, the company has thus built up an unrivaled degree of experience and insight into designing and building microwave communication systems for difficult terrains. NERA is keen to share its knowhow with Pakistani clients, and the company has set up its own permanent office in Islamabad.

Indeed the need for sophisticated industrial control systems such as the one being inaugurated today by WAPDA, combined with the spectacular growth of private mobile telephone services and the increasing industrial interest in exchanging information with trucks, vans and executives on the road, (not to mention the ever-vigilant defence sector) all point to a very bright future for microwave radio links.
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Copyright 1991 Gale, Cengage Learning. All rights reserved.

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Publication:Economic Review
Date:Mar 1, 1991
Previous Article:Privatizing Telecommunucations Systems: Business Opportunities in Developing Countries.
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