|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