Special Issues at Low frequencies: Calibration
	• Nançay present solution: – Uses only Cygnus A radio-galaxy, which gives a strong signal at 5000 l and 500 MHz – Uses a 2 components model, and fits fringes – Accuracy could be better for long baselines – Starting a new procedure based on redundancies and short baselines: antennas are calibrated step by step, and almost no source model is needed.