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Accession Number:
ADA193324
Title:
A Notch Filter Instrument for Measuring ELF (Extremely Low Frequency) MSK (Minimum Shift Keying) Signals.
Descriptive Note:
Technical rept.,
Corporate Author:
IIT RESEARCH INST CHICAGO IL
Report Date:
1988-01-01
Pagination or Media Count:
101.0
Abstract:
This report presents a notch filter technique for measuring extremely low frequency ELF signals in the presence of other higher-level, low frequency voltages, specifically 60 Hz and harmonics, on public utility systems. The report also describes the design, development, and operation of a special-purpose notch filter instrument that allows the practical realization of this measurement technique. The instrument, called the Notch Box III, is compact 2.75 x 10 x 9 in., lightweight less than 4 lb, and battery operated for complete electrical isolation and portability of its electronic circuitry. It features input buffering and selectable attenuation, input overload warning, a narrow-band 60 Hz notch filter with greater than 80 dB of attenuation, a Chebyshev low-pass filter providing sharp roll-off above 100 Hz, output signal buffering, and battery charge status indication. The Notch Box III can operate 150 hours on a single battery charge. Keywords Extremely low frequency Interference mitigation Active filter Notch filter Interference measurement Noise measurement Instrumentation.
Distribution Statement:
APPROVED FOR PUBLIC RELEASE