Experimental Results of VLF Dipole Tests on the Greenland Ice Cap

Abstract

Results of measurements on lung resonant dipoles installed un the Greenland ice cap are presented. The difficulties involved in laborat~ry modeling of VLF antennas are discussed and the full-scale data presented show significant differences from previously reported model data.· Self-impedance, amplitude current distributions. and relative efficiency were measured using dipoles that ranged in length from 600 m to 8.000 m. Results from three 3.700-m dipoles having different insulation diameters are (•umpared. Four-electrude measurements of complex conductivity of the surface ice are also reported. Dipole driving point resistance at resonance is found to be higher than expected. and a basic (·urrelation of reo;onant length and driving point resistance with the dielectric properties of the ice is noted. The efficiency uf insulated dipoles was found to be significantly greater than that of uninsulated dipoles of equivalent length.