Satellite Miscommunication

During my first trip to Mexico, I was invited to teach and do some research in satellite-communication technology. The research center, named CINVESTAV, was located in the northern district of Mexico City.

Having taught several master's courses on communication technology, I also wrote a Spanish textbook for my students on satellite communications. My courses were also attended by external students and industry technicians.

One day I was invited to teach a short course on satellite communication technology at a large mining company headquartered in Mexico City. The course took one week. The students, engineers, and technicians were good. They did well on a written test their company required.

When the class was completed, one of the company's executive officers revealed the reason for the class. The company had purchased a dozen earth stations for mining plants. They also rented a satellite channel.

The hardware was purchased in the US, where the engineers had also received training. The executive told me that the company knew how to control the communication system by preprogrammed computers, but they had no practical experience with the hardware.

After installation, one of the earth stations had a problem with a noisy channel. The boss sent his engineers to yet another course to learn the secrets of the hardware. Yet the new knowledge was not sufficient to solve the station's noise problem.

Finally, they asked me to bring my experience to the problem. At the time, I was busy with other courses, so I asked my best student, Juan, to go in my place and test his skills. Before he went, I recommended that he try to reposition the antenna. I had erred with antennas years earlier and knew the antenna could be the source of the noise problem.

Satellite earth-station antennas with a large gain have side lobes, and during pointing, the side-lobe signal can seem to be strong enough, but the large gain can produce noise in the channel. A more careful pointing to the main lobe can solve the problem.

The day after the action, Juan returned and happily reported, "Yes, professor, that was it!" He was well rewarded financially for his trip, but the best reward was that he corrected the problem.

This entry was submitted by Jiri Polivka and edited by Rob Spiegel.

Jiri Polivka was born and educated in Czechoslovakia. He received an MS and a PhD equivalent from the Czech Technical University in 1961 and 1975. He then worked with the A.S.Popov Radio Communication Research Institute and the PTT Research Institute in Prague from 1975 to 1988. His worked focused on satellite-communication technology and microwave propagation research. In 1989 and 1990, he was an invited professor to the Mexican Center for Investigation and Advanced Technology. In the mid 1990s, he joined Spacek Labs in Santa Barbara, Calif.

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