LOFAR antenna development and initial observations of solar bursts

• Published in: Planetary and space science Vol. 52; no. 15; pp. 1351 - 1355
• Main Authors: Stewart, K.P., Hicks, B.C., Ray, P.S., Crane, P.C., Kassim, N.E., Bradley, R.F., Erickson, W.C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-12-2004
• Subjects: Antennas; LOFAR; Solar radio astronomy; VHF; VHF; Solar radio astronomy; HF; Antennas; LOFAR
• ISSN: 0032-0633; 1873-5088
• DOI: 10.1016/j.pss.2004.09.014

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
1
8
to one wavelength long and the feedpoint is less than
1
2
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.