AAS 207th Meeting, 8-12 January 2006
Session 136 Long Wavelength Array
Poster, Wednesday, 9:20am-6:30pm, January 11, 2006, Exhibit Hall

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[136.02] Characterizing Active Antennas for the Long Wavelength Array

N. Paravastu, B. C. Hicks (Naval Research Laboratory), R. Bradley, J. R. Fisher (National Radio Astronomy Observatory), A. Kerkhoff (Applied Research Laboratory), S. Ellingson (Virginia Polytechnic Institute), K. P. Stewart (Naval Research Laboratory), Y. M. Pihlstrom (University of New Mexico), W. C. Erickson (University of Tasmania), N. E. Kassim, P. S. Ray, K. W. Weiler (Naval Research Laboratory)

The Long Wavelength Array (LWA) is a developing dipole antenna-based radio telescope intended to operate in the 20 –- 80 MHz frequency range. Elements of this array will be active dipoles, the design of which will be chosen based on simplicity, affordability, and broadband qualities. Currently, work is in progress to characterize a blade dipole antenna with an active balun –- the element of the Long Wavelength Demonstration Array (LWDA). Microwave Studio, a 3-D electromagnetic simulator, was used to calculate the frequency dependent impedances and field patterns of the blade antenna. The simulation results were then used to determine sky noise –- to –- system noise ratios for the blade antenna/balun combination as a function of frequency. The objective is to design an active antenna that exhibits sky noise dominant performance. Simulations are now being used to corroborate field measurements made at the National Radio Quiet Zone in Green Bank, WV, as well as the LWDA site near the VLA in New Mexico. Preliminary sky noise and antenna impedance measurements show excellent agreement with simulated predictions. Lessons learned from work on the LWDA antennas will be applied to the design of the LWA antennas. Basic research in astronomy is supported by the Office of Naval Research.

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