English

DTIC ADA323045: A Comparison of Modelled and Measured HF Antenna Array Patterns.

The relative-phase response and gain patterns found by numerical modelling of an HF antenna array of vertical whip antennas were compared with the patterns found by actual measurements. While some features of the measured patterns agree with the model, other significant features did not. The disagreement could be due to ground inhomogeneities and other local features as well as differences between the actual and modelled antenna array such as discrepancies in antenna position and orientation, poor connections to ground radials, and differences in the modelled and actual antenna loading. In most cases where the elements were closely spaced, numerical modelling provided a somewhat better estimate of the antenna gain and relative-phase response patterns than the simple assumption of azimuth-independent gains and a relative phase response consistent with a spherical wavefront centered on the transmitter. However, for more remote antenna elements, modelling did not provide a better estimate; nor did it provide a better estimate for the lowest modelled frequency. Actual pattern measurements, on the other hand provided significantly better pattern estimates in all cases.

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