Joseph E. Ferris

Ground and flight test results for standard VOR and double parasitic loop counterpoise antennas

Results of ground and flight tests carried out at 109 MHz to study the vertical plane radiation patterns of standard VOR and double parasitic loop counterpoise antennas above ground are discussed. The ground tests consist of the measurement of the fields produced in the quasi-radiation zone of the test antenna The flight tests consist of measuring the far field with the help of an aircraft flying at a constant altitude along chosen radial paths to and from the test antenna. The reduced test results are compared with available theoretical values.

A double parasitic loop counterpoise antenna and its application to aircraft navigation systems

The radiation properties of a double parasitic loop counterpoise antenna capable of bringing out superior performance from the existing VHF omnirange (VOR) systems are discussed. It is shown that such an antenna when suitably designed will reduce considerably the siting errors inherent in the existing VOR systems.

Measurements of television interference caused by a vertical-axis wind machine. Final subcontract report

The electromagnetic interference to television reception caused by the 17 m Darreius at Albuquerque, NM, has been studied by carrying out measurements at a number of sites in the vicinity of the VAWT. The rf sources used were the commercial vhf and uhf TV signals available in the area. Ambient field-strength measurements showed that the signals on all TV channels except one were strong, and provided good reception at all test sites. With the antenna (properly) oriented for maximum direct signal, unacceptable interference was observed on some channels at sites out to 33 m from the WT in the forward and backward regions. With the antenna beam directed at the WT, interference varying from slight to violent were observed at all sites on some or all TV channels. A simple theoretical model has been developed for analyzing the TVI produced by a VAWT like the Darrieus. Using the model in conjunction with measured data, an approximate expression for the equivalent scattering area A of the Darrieus has been developed. It is found that A is wavelength (lambda) dependent and varies as lambda/sup 1/2/.

Theoretical and experimental study of arrays of axial slots on a circular cylinder

Abstract : The radiation patterns produced by arrays of axial slots on a conducting circular cylinder of infinite length are studied theoretically and experimentally. The required phase of excitation of elements to produce a beam in a certain direction are obtained by approximating the array by a section of a circular array of isotropic sources. For the given radius of the cylinder and the frequency band of interest, the approximation is found to yield satisfactory results. Radiation patterns produced by arrays of 2, 3 and 4 axial slots are numerically computed and discussed. Theoretical results are also compared with measured results and the agreement between the two has been found satisfactory.