Tech Article

Vignettes by Roger Freeman

This collection from Roger Freeman reflects his experience and background across the board in telecommunications -- you'll find vignettes on bandwidth, performance predictions, telecommunication terminology and reliability, availability and maintainability.
Bandwidth 101
Many people seem to confuse bandwidth with "bit rate capacity." Here Roger explains the very basic differences bringing in the work of H. Nyquist and Claude Shannon, early pioneers in information theory.

Performance predictions valid for indoor and outdoor paths
In this tip Roger briefly covers basic performance prediction methods needed for planning and installing wireless (radio) systems in the enterprise environment.

Line-of-sight may not be good enough
If I can see the distant end antenna, there is line-of-sight and a good microwave path. Possibly not so, Roger states. Many people leave out obstacle clearance criteria using a Fresnel zone relationship. A table is provided giving a number of 0.6 Fresnel zone clearances.

Confusion in telecommunication terminology
Historically, in telecommunications there were two distinct worlds: (1) switching and (2) transmission. Learn about the distinctions here…

Reliability, availability and maintainability
Ideally any telecommunication or IT system should be able to operate indefinitely without degradation. He relates these three key parameters in a simple equation. Get Roger's synopsis here.

Roger Freeman is a widely recognized expert in telecommunications system engineering. Roger has worked in telecommunications since 1946 when he joined the Navy and became an aviation radioman. Later, Roger served as a radio officer in the merchant marine for nearly 10 years. He then held several positions with ITT assigned to their Spanish Standard Electrica subsidiary. He also served the International Telecommunication Union as Regional Planning Expert for Northern Latin America based in Quito, Ecuador. Roger is bilingual. His last employee position was principal engineer with the Raytheon Company, Marlboro, MA where he took early retirement in 1991 to establish Roger Freeman Associates, Independent Consultants in Telecommunications. He has been giving seminars in telecommunication disciplines at the University of Wisconsin, Madison for nearly 20 years. Roger has been writing books on various telecommunication subjects for John Wiley & Sons since 1973. There are seven titles, which he keeps current including the two-volume work, Reference Manual for Telecommunication Engineers, now in 3rd edition. He holds two degrees from NYU. His Web site is and his e-mail address is

Here are Roger's landmark books:

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