Wireless Communications Overview

Radio Propagation Basics

The following diagrams show different modes of radio propagation.

Diagram of radio propagation


Range is dependent on radio transmit power, cable losses, antenna gain, and radio path losses, and receiver sensitivity. To maximize range, one has to minimize losses, and maximize transmit power and sensitivity. Radio path losses are minimized by optimizing antenna locations and tower heights to achieve maximum clearance over obstructions. Where line of site cannot be achieved, repeaters can be used to extend range. With line of site path, a range of 25+ miles can be achieved with spread SCADALink spectrum equipment.

Line of Site

A line of site path is desirable but not totally necessary for radio data communications. For optimum radio communications range, a line of site radio path is desirable since path obstructions will attenuate radio signal as well as cause multipath conditions. The more the path is obstructed, the more losses will be incurred. As long as an adequate and consistent signal level is received the radio path will be adequate. For shorter distance applications with low free space path loss, large obstruction losses can be tolerated.

Where a line of site path is not available there is more chance for multipath conditions which may cause reduced and inconsistent receive signal levels. Non-line of site paths may be perfectly operable if consistent reflected signals from man-made reflectors such as buildings or natural reflectors such as rock faces are present.

Frequency hopping spread spectrum technology used in SCADALink radio products offer frequency diversity giving higher immunity to multipath conditions (nulls at one frequency are frequently not nulls the next frequency). This frequency diversity also allows a lower fade margin to be implemented successfully.

Radio Signal Path