Air/Undersea Communication at Ultra-Low-Frequencies Using Airborne Loop Antennas
Abstract
In this report we investigate the possibility of using ultra-low- frequency (ULF) signals from airborne loop antennas (i.e., magnetic dipoles) for air/undersea communication. Because of the low data rate at ULF, communication is here understood to mean the transfer of short messages of high information content. We use numerical integration to calculate the 1 Hz total magnetic field amplitudes in the sea at depths from 0 m to 200 m due to airborne unit moment vertical and horizontal magnetic dipoles at altitudes from 100 m to 10 km. Considering the magnetic moments m attainable with present aircraft power and payload capability (m = 10 to the 7th A sqm - 10 to the 9th A sq m and the minimum detectable amplitude for a 1 Hz signal beneath the sea (approx. 1 m sub gamma, we conclude that air/undersea communication at 1 Hz is possible under the following illustrative conditions: for a horizontal plane loop antenna at 3000 m altitude and a ULF receiver at a 100 m depth, communication is possible for horizontal distances to 10 km for m = 10 to the 7th a sq m and to 33 km for m = 10 to the 9th A sq m. The corresponding limits for a vertical plane loop antenna are 13 km to 64 km. It is also possible, if desired, to limit communication to a comparatively small circular area circular area directly beneath the aircraft. Sea floor effects can alter these values significantly, particularly if the receiver is near the floor.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1977
- Accession Number
- ADA042132
Entities
People
- Antony Fraser-Smith
- D. M. Bubenik
- O. G. Villard Jr.
Organizations
- Stanford University