The effective conductivity of a potential antenna site is a measure of the field strength that an antenna built on the site would radiate. Only in special cases, however, is this same measure suitable for characterizing the power that the antenna would dissipate. It is shown that in the case of a current-sheet antenna built on a horizontally stratified half-space, a measure that characterizes both the radiation and dissipation properties of the site is the complex surface impedance. This same measure remains substantially valid for an antenna composed of separate cables and for inhomogeneous half-spaces of not too great lateral variation. The most reliable methods of measuring the surface impedance are theE/HandH/Imethods, provided both include the measurement of the phase of the ratio.

The surface impedance concept is used to examine the effect of ground anisotropy on the radiated field and power dissipation of a horizontal ELF transmitting array. The principal result, for a simple homogeneous but anisotropic ground, is that even though the ground skews the antenna pattern, any attempt to reorient the array to steer the pattern peak towards the receiver incurs an increase in power dissipation. In fact, the power dissipation is minimized by steering the pattern peak even further away from the receiver.

The impedance, effective length, and current distribution of a grounding electrode are examined numerically. Its length varies frown being electrically short to being larger than a skin depth. The electrode is taken to be the bared extension of an insulated buried antenna. It is shown that there is little to be gained in making the electrode longer than a skin depth, unless the current distribution can be forced to spread out further along the electrode. Whether or not the properties of the grounding electrode will be affected by the impedance per unit length of the conductor is an important consideration. A criterion to help in this regard is developed.

A solution is obtained to the problem of finding the current distribution in a buried linear antenna which minimizes the dissipated power while maintaining the required radiated field. An example shows that such distribution saves about 30 percent on power dissipation compared to an antenna of the same total length having simple bared-end grounding terminations. A practical method using current transformers is proposed for controlling the current distribution. A grounding system using this method has the property that it does not short out adjacent active antenna cables when it is in standby mode.

The pressure fluctuations in the turbulent boundary layer surrounding the towed antenna cable cause it to vibrate in the geomagnetic field and thereby generate noise. This noise mechanism is the dominant one in current long antennas. Its effect can be reduced only by increasing antenna diameter and length. Tension, stiffness, and damping have no effect. Noise voltage spectra derived from pressure fluctuation data show striking agreement with those measured.

A recurrence technique is described that enables the use of proven efficient Fourier transform techniques to be applied to the expansion of a given function in terms of spherical harmonics.