Solar Total Power Radio Interferometer

Total power solar radio interferometer composed of two WiFi antennas at an East-West distance of 8 m, a down-converter and a Callisto spectrometer. While the sun moves through the beam pattern the receiver detects this interference pattern. By analyzing this pattern, the radio-diameter of the sun can be obtained. This even during bad weather conditions like snowfall or fog. Observation was made by students of ETH Zurich during Astrowoche 2013 at Diavolezza, 3000 m asl. The diameter was found to be in the order of 0.65 degree. The value will be statistically improved in the coming days.

WiFi-antennas in the snow, south of Hotel Diavolezza pointing to meridian transit of the sun.
Signals of both antennas are first amplfied by ~20dB, then fed into a Wilkinson-power combiner. The combined signal is fed into an S-band down-converter (KUHNE-Elektronik Germany). The IF output of the converter is fed via a long 50 ohm coax into the observatory and to a Callisto spectrometer.