© ASTRON
Measurements were done at four different azimuthal positions of the array, spaced at 45 degrees. Noise measurement results for the individual positions, as well as their average are presented, showing mean values below 45 K, with a standard deviation of 1-2 K.
Furthermore, we present results on the reproducibility of noise measurements with the experimental 60-element Medium Sized Tile (MST), for one polarization of its 5x6 array. Seven measurements were done at one hour intervals during the day, between 9:30 and 15:30. Results of the individual measurements and their average show values below 45 K, with a standard deviation smaller than 1 K. As may be observed from the concerning noise plot, results for some of the measurements between 1150MHz and 1250 MHz that were strongly affected by RFI, have been omitted. These frequencies showed large noise temperature peaks in a number of measurements during the day, with much larger standard deviations.
In the present results for the MST we observe a 5 K noise temperature increase, compared to the results in the AJDI of 26-05-2014. A possible explanation for this difference is the influence of low level RFI on the measurements, which is subject of further investigation.
The third noise plot shows a comparison of the averaged noise temperatures for the 1 m2 tile and the MST. The results are quite close to each other, indicating that the measurements on the smaller MST with respect to the 1 m2 tile, give a good indication of the noise performance of a larger array. This allows lower cost and easier handling for this type of array experiments.