Comparison of predicted aircraft wire antenna terminal impedance (using NEC) with measurement in the HF band

The author gives an indication of the accuracy attainable with RF numerical methods in the prediction of those quantities which depend upon the near-field of radiating structures. A wire-mesh RF mathematical model of a medium size airliner is described. Using this model, and with NEC as the solution code, predictions are presented of the terminal reactance of an installed 'long-wire' HF antenna. These represent true predictions rather than 'post-dictions' because the RF mathematical model does not incorporate any empirically derived information. The difficulties involved in obtaining the corroborative measurements are examined and direct comparison with the predictions is made. The particular antenna configuration chosen for this study is considered to constitute a stringent test of the predictions. The agreement between calculation and subsequent measurement is fair.