Evaluation of simple aerospace antenna coupling prediction techniques

Friis equation gives accurate results for antennas in line of sight of each other, and it's important to predict the gain of the antennas accurately. For predicting the coupling between antennas not in direct line of sight; Lyon and B&S are good for low horizontal displacement; Siegel's equation is good at frequencies below 500 MHz & above 5000 MHz (Weston [8]). In the Siarkiewicz and Adams equation, the TALF and LAR factors had little effect on the results. RALF is a useful correction factor: RALF less than 1/4 λ the correction value is too small, and RALF greater than 1/4 λ the correction value is too great. Simplified equations can give reasonably accurate results and follow trends. The model must not be used outside the parameters they were originally created. Strict rules must be set out for their use, including size of model.