CHAPTER 6
Radio energies in the ELF and ULF spectra were each reexamined as means for establishing powerful new communications throughout the world. Headed primarily by Galejs, Watt, and Christofilos, ELF radiowave systems found their strongest supporters in the academic circles. A tremendous amount of preliminary study and experimental work preceded the actual construction of SANGUINE. The Naval VLF station at Jim Creek was driven down to an operating frequency of 4000 cycles per second in a test which spanned the continent. Successive testing brought this operating frequency further down, to 100 cycles per second. Tests, conducted on the propagation of yet lower harmonics across the continent and planet itself, came through and among Naval VLF stations. Toward the development of a true and operable ELF transmitter, military engineers attacked each problematic facet of the ELF art. ELF radio transmitters had far more stringent requirements than VLF stations, and would be enormous in actual size. The radiating structure was the main problem. How would a system of this size manage its electrical supply? Maintaining a consistent ELF current throughout a huge aerial array would require the antenna to adopt new geometrical dispositions. For the design of these new structures, a methodic study of older ground conduction systems was engaged. Of particular note were the articulate buried well terminals of Fr. Joseph Murgas. Murgas antennas (1906) were more like terminals than wave antennas. Since traditionally accepted antenna lengths did not limit Murgas antennas, they were studied with great interest by those planning the SEAFARER system.
The Murgas system employed vertical ground rods. In early systems, Fr. Murgas simply drove very long rods into the ground with hammers. Later designs were far more visionary in aspect. Wells were sunk to very great depths for their original purpose of achieving transcontinental or transoceanic communications. In some of the Murgas designs energetic transfer was achieved by direct conduction with the rock walls. In variations, an insulative seal was maintained with surrounding rock strata, Fr. Murgas often implementing water or oil filled wells. Finding these designs capable of powerfully transmitting ELF signals, Murgas antennas were employed in propagation experiments all along the eastern coast of North America (1964). Tests were conducted at 50 kilocycles, using 300 meter deep wells.
Variations of the Murgas method proved that rock conductivity does indeed provide an important subterranean communications channel, the variations of rock strata and rock attributes being critical. The efficiency of these transmissions were found to vary with rock conductivity. Specific stations would therefore be established toward achieving these increased efficiencies. Murgas antennas did not have to be as long as the waves by which they were energized, their operation depending on largely unstudied phenomena. When proper geological strata were found, horizons of conductive and insulative rock, transmissions produced anomalous efficiencies. The Murgas system provided vocal communication to unheard distances. When driven at Extra Low frequencies, these deepwell conduction antennas transmitted great power.
Other experiments employed natural structures as ground antennas of huge extent. Coastal geological formations of iron clays between strata of highly insulative sandstones represented an engineering dream. Requiring no construction work other than the drilling of power injection wells, these geological antennas could be established wherever similar conductive-insulative conditions were present. Applications of ELF directly into these geological strata produced interesting and classified results which served Naval experiments in deep subsurface communications. There were those RCA engineers who, for purely commercial reasons, insisted that true “wave type” antennas would produce better results. They were wrong. Rogers type antennas were buried at some slight depth or simply laid along the ground surface, being energized at 70 Kilocycles. Rogers antennas suffered from certain reflective distortions, increasing in efficiency with increased frequency.
SANGUINE Before building the SEAFARER system, military engineers examined all the previous work in VLF and ELF transmission. Several specialists began examining all propagation aspects of the new deep-sea communications frontier, the greatest concern being the security of signals so employed. Command base transmitters would be monstrous in size, definitely located in the American heartland. ELF communications would employ specially designed AC generators, identical to conventional power machines. If traditional wave antennas were to be used, then the efficient transfer of these currents to the earth itself required radiating structures of extreme dimensions. In fact, these ELF aerials would dwarf those VLF structures used in the first Marconi Stations. The theoretical halfwave dipolar aerial for a 100 cycle generator required 1400 kilometers of cable! It was obvious that other modes of energetic transfer would be crucial to the success of the proposed system. There were those whose early research produced subterranean radio systems. Murgas and Rogers were able to transmit and receive radio signals through the ground. Using both monopolar and dipolar aerials, each system represented a possible answer to the military dilemma.
Conductivity radio was a study area largely ignored and forgotten. Air Force experimenters reinvoked the forgotten technologies. Murgas antennas were more like terminals than wave antennas. Since traditionally accepted antenna lengths did not limit Murgas antennas, they were studied with great interest by those planning the SEAFARER system. The Murgas system employed vertical ground rods sunk to great depths. Finding these capable of powerfully transmitting ELF signals, Murgas antennas were employed in propagation experiments all along the eastern coast of North America. Tests were conducted at 50 kilocycles, using 300 meter deep wells. Variations of the Murgas method proved that rock conductivity does indeed provide an important subterranean communications channel. The efficiency of these transmissions were found to vary with rock conductivity. Specific stations would therefore be established toward achieving these increased efficiencies. Murgas antennas did not have to be as long as the waves by which they were energized, their operation depending on largely unstudied phenomena. These deepwell conduction antennas transmitted great power at extra low frequency.
Variations of these experiments employed natural structures as huge ground antennas. Coastal geological formations of iron clays between strata of highly insulative sandstones represented an engineering dream. Requiring no construction work other than the drilling of power injection wells, these geological antennas could be established wherever similar conductive-insulative conditions were present. Applications of ELF directly into these geological strata produced interesting and classified results which served Naval experiments in deep subsurface communications.