Friday, 2 November 2012

First Light: Tri-Static VHF Radar

On 1st November 2012, EISCAT carried out the first tri-static experiment with the VHF transmitter in Tromsø and the remote dishes in Kiruna and Sodankylä, which had been converted to the VHF frequency of 224 MHz earlier this autumn. Good signals were immediately seen at all sites, with Signal-to-Noise Ratios (SNR) exceeding 10%.

VHF Reception at Tromsø.
The monostatic part of this experiment was a test run low-elevation Common-Program runs with extra long ranges to be carried out in December, but during this particular test experiment the antenna was pointed vertically. The beams from the remote 32-m dish antennas in Kiruna and Sodankylä intersected the transmitter beam at the F-region peak at 270 km. The transmitter sent a circular polarised signal at 223.6 MHz.

VHF at Kiruna, Sweden (left) and Sodankylä, Finland (right).
However, in this test, the remote sites received signals only in horizontal polarisation, which is currently the only polarisation, which has a calibration noise source connected. It will take a couple of months to finalise the project with fully calibrated signal together with a software polariser in order to take into account the Faraday rotation, which the signal gets on the way from the scattering volume to the remote antennas.

With these fantastic first results we wish all of you a very good weekend!

Text and images: Adapted from Ingemar Häggström.

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