Rejection of radio-frequency noise with a wide-band differential preamplifier and solid-shielded coaxial input cables

Conference · Sun Feb 01 04:00:00 EST 1976 · IEEE Trans. Nucl. Sci., v. NS-23, no. 1, pp. 375-382

OSTI ID:4044209

Burns, R S; de Lorenzo, J T

Radio-frequency signals simulating electrical interference ranging from 50 kHz to 50 MHz were applied to the shields of the input cable system (two solid- shielded, mineral-insulated cables approximately 6 m long) of a wide-band (approximately 60 MHz) differential preamplifier for fission counters to determine the common-mode rejection. Results show that differences in electrical properties and shielding characteristics of the two input coaxial cables along with end effects produced by an unbalanced sensor severely degrade the rejection capability of the differential preamplifier. At 1 MHz, the common-mode rejection without input cables is approximately --70 dB; this is reduced to approximately -- 10 dB when measured with the rf signal applied to the surface of the input cable shields. Measurements of the shielding characteristics of the input cables showed resonances at test frequencies greater than 2 MHz. A ferrite core was installed in the input assembly to increase the impedance of the shields and to permit termination of the coaxial line consisting of the input cable shields and the protective metal conduit for the input cables. This assembly eliminated all resonances below 20 MHz. The increased impedance also reduced the amplitude of the shield currents, resulting in an increase in the shielding effectiveness of the input cables without affecting the signal transmission of the cables. (auth)

• Research Organization: Oak Ridge National Lab., TN
• NSA Number: NSA-33-029453
• OSTI ID: 4044209
• Conference Information: Journal Name: IEEE Trans. Nucl. Sci., v. NS-23, no. 1, pp. 375-382
• Country of Publication: United States
• Language: English

Related Subjects

*COAXIAL CABLES-- SHIELDING
*FISSION CHAMBERS-- COAXIAL CABLES
*LMFBR TYPE REACTORS-- FISSION CHAMBERS
440300* --Instrumentation--Miscellaneous Instruments
IMPEDANCE
IN CORE INSTRUMENTS
INTERFERENCE
N46400* --Instrumentation--Miscellaneous Instruments
N77500 --Reactors--Power Reactors
Breeding
NOISE
PREAMPLIFIERS
RADIOWAVE RADIATION
RESONANCE