Transmitter Power

Author: Edmund A. Laport

Assuming optimum radiation engineering for a circuit (frequency, antennas, noise, etc.), a certain amount of effective radiated power is necessary to maintain operating margins over a satisfactory proportion of time. Except for multipath propagation, the principal circuit requirement is that the received signal-to-noise ratio be above a certain minimum. When all other means to this end fail, more transmitter power can be used. Considering the range of variation in signal-to-noise ratio characteristic of high-frequency operation, especially on long circuits, operating economics become an evaluation of the cost of transmitter operation versus the increased percentage of time the minimum operable signal-to-noise ratio is received.

Sometimes enormous power increases would be necessary to make an appreciable improvement in the operating circuit. In such cases it may be far more effective to apply every possible means for decreasing fading range than to increase power. Diversity reception is always a help in such cases, because it reduces the fading range and makes use of the strongest of two or three arriving signals. Too often, however, excessive power is employed to override other engineering deficiencies, incidentally causing unnecessary interference with other services.