Very Low Frequency Propagation in the Earth's Crust Below the Ocean.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO SCHOOL OF ENGINEERING
Pagination or Media Count:
The feasibility of using the earths crust under the oceans as a communications channel for very low frequency waves was studied. The structure of the crust and its electrical properties were used to evaluate the conductivity-depth profiles found in the literature. Using the impedance, E sub xH sub y, a new phase function was defined that not only made the phase changes at the boundaries of the waveguide explicit, but also allowed the use of a computer for calculation of the propagation and attenuation constants. The system noise was assumed to come from two main sources atmospherics and thermal effects. Calculation showed that beneath the ocean the atmospheric noise could be neglected. The thermal noise within the waveguide was calculated to be -162 dBm. The attenuation for the TM sub 10 mode was calculated to be -1.35 dBkm, thus allowing a transmission range of only about 163 km for 1 kW of transmitted power. The conclusion was that the crust under the ocean was not feasible as a long-range communications channel at VLF for the TM sub 10 mode.
- Geology, Geochemistry and Mineralogy
- Radiofrequency Wave Propagation