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Electromagnetic Retransmission System for Locating Trapped Mine Workers.

Authors
Raab-FH; Hansen-PK
Source
NTIS: PB/81-215329 :268 pages
Link
NIOSHTIC No.
10002117
Abstract
The electromagnetic retransmission system is a new, automated method of locating trapped mine workers. This technique overcomes many limitations inherent in electromagnetic direction finding by reducing the effects of the conducting ground to an acceptable maximum, by finding position accurately in the presence of antenna tilt, and by eliminating the need for the receiver to be located directly above the subsurface transmitter. Three transportable three-axis magnetic-dipole transmitters on the surface create a system of electronic grids in which the phases of the downlink signals convey position information. The subsurface retransmitter modulates the uplink carrier of the existing beacon transmitter with the received downlink signal; the coal-pillar loop antenna is used for both receiving and transmitting. The uplink receiver uses a three-axis antenna and extensive digital signal processing. A small computer integrates data, estimates position, and controls system operation through VHF-FM communications. Both coal-mine and deep- mine operations are possible by selecting appropriate transmitting power and signal frequencies.
Publication Date
19800101
Document Type
CP; Final Contract Report;
Fiscal Year
1980
NTIS Accession No.
PB81-215329
NTIS Price
A13
Identifying No.
OFR 48-81
NIOSH Division
PRC;
Source Name
NTIS: PB/81-215329
Performing Organization
Polhemus Navigation Sci. Inc.
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