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LOFAR antenna development and initial observations of solar bursts

Authors:	KP Stewart BC Hicks PS Ray PC Crane NE Kassim RF Bradley WC Erickson

Institution:	^aNaval Research Laboratory, Remote Sensing Division, Code 7218, 4555 Overlook Avenue SW, Washington, DC 20375, USA ^bNaval Research Laboratory, Space Science Division, Washington, DC 20375, USA ^cNational Radio Astronomy Observatory, Charlottesville, VA, USA ^dBruny Island Radio Spectrometer, Lighthouse Road, Bruny Island, Tasmania 7150, Australia

Abstract:	We are developing and testing active baluns and electrically short dipoles for possible use as the primary wide band receiving elements in the low-frequency array (LOFAR) for long wavelength radio astronomy. Several dipoles of various designs and dimensions have been built and tested. Their useful range occurs when the dipole arms are approximately to one wavelength long and the feedpoint is less than wavelength above ground. An eight-element NRL LOFAR test array (NLTA) interferometer has been built and fringes have been observed from the brightest celestial sources in the frequency range from 10 to 50 MHz. The antenna temperatures vary from about 10% to 100% of the average brightness temperature of the galactic background. With these parameters it is easy to make the amplifier noise levels low enough that final system temperature is dominated by the galactic background.

Keywords:	LOFAR Solar radio astronomy HF VHF Antennas
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