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27th of February 2018
The Culgoora Radioheliograph 43 MHz Antenna
One of last week's ADAP's showed an antenna of the Culgoora Radioheliograph, an array of 96 dishes spaced around a ring with a 3km diameter which operated at 80 and 160 MHz. The Radioheliograph also operated (from 1973) at a frequency of 43 MHz, using a co-located but separate array of antennas. One of these is pictured above: it is of corner-reflector design, an antenna type invented by John Kraus in 1938 and commonly used for tv aerials. Corner reflector antennas commonly have an opening angle of 90 degrees: as shown above the radioheliograph antennas used a somewhat wider opening angle in order to track the sun at reasonable sensitivity over a 4 hour range centred on its meridian transit (roughly, local noon). The 43 MHz array consisted of 48 antennas spaced around a ring with a 2.775 km diameter in order to provide an aperture (measured in wavelengths) that was half that of the 80 MHz array. The active element of the antenna was a folded dipole feed, which in the antenna above is clearly no longer operational! (Image credit: P. Edwards).
More details of the antenna are given in Sheridan et al. 1973, Proc. IEEE, vol. 61, p. 1312

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