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 heardand. 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 eeirth 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 <md 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 antetmas were more like terminals than wave antermas. 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 direcdy 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. Rogers type antermas, buried at some slight depth or simply laid along the ground surface.

Suffered from reflective distortions. Energized at 70 kilocycles, Rogers antennas increased broadcast efficiency with increased frequency. To satisfy contractual obligations, some combination of both designs was sought. Spanning great area, the SEAFARER ELF signalling system is a matrix of small power transformers, raised lines, and ground plates. SEAFARER went operational in 1989 broadcasting coded messages on an assigned carrier frequency of 76 cycles per second.

In sites which have been loudly announced by government publications, the SEAFARER system pumps the earth with ELF power of closely monitored intensities in both Michigan and Wisconsin. SEAFARER uses the multiple ground system, the entire array behaving as a conduction strip of great extent ELF aerials may be rectilinear or circular. Properly phased ground currents are driven back and forth along the miles-long strip of chosen geology. The weak alternating disturbance spreads outwcu'd for thousands of miles. The Wisconsin aerial consists of two lines, each 14 miles long. The Michigan aerial consists of 3 lines; two of 14 miles length and one of 28 miles length. Both systems are phase coordinated. Both aerials must work in tandem, each broadcasting a piece of the total communications intended at any instant. Phase coordination permits ELF radiation without the need for an excessive physical structure by creating coordinated electromotive tensions. Each link in the ELF antenna pulses any singular signal along.

The SEAFARER system is a poor solution to an otherwise impossible requirement. Phased wave integrity between the two sites is exact. With coordinated electromotive tensions existing between the two sites, the ELF signal conductively spreads through the long groundpath. Unfortunately there is destructive interference of a degree which seriously limits the total amount of dipole radiated ELF. Ground currents neutralize at each successive ground plate in the phase sequence. Consequently, not much ELF actually disperses to greater distances. This is why the excessive generators are required. Ever more obvious with time, radiowave communications become less preferred commimications chaimels. While SEAFARER was being completed, another communications development was already making ELF obsolescent. The deployment of high orbital geostationary satellites, coupled with the development of highpower multispectrum lasers, gave military hierarchy a superior commimications system which already exceeds the capabilities of radio.