2018 March
Mar 15
11:26 UT Since 2018 March 8, we have not been taking regular observations due to installation of the notch filters in all of the FEMs. This gives us full 1-18 GHz frequency range. Installation of the filters has proceeded at a pace of about 2 per day, and as of this morning only 2 remain to be installed (ants 12 and 13). Some occasional observations for calibration and checking have continued, but they will not be useful for science because the system has been very far from optimized (both signal levels and delays). This morning I have done an FEM-INIT and DCM table calibration for ants 1-10 (ants 12-14 are also done, but not relevant), and am doing some calibrator observations on both HI and LO receiver for setting delays on those antennas. One thing I notice is that the delay phase vs. frequency now has a much steeper "U" shape, similar to what we were seeing on Ant 5 (which already had notch filters installed). I believe it will be necessary to correct for this phase shape (which should be stable) in the dppxmp program.