The ionosonde is radar that emits vertically signals in the 1 to 20 MHz frequency range, which are reflected in the ionosphere. The analysis of the signals of different frequencies transmitted and received by the system gives the vertical electron density profile. The ionosonde we operate at Brazilian Antarctic Station EACF is a ‘Canadian Advanced Digital Ionosonde’ (CADI). It operates simultaneously in two distinct modes, the first one transmits six frequencies (between 3 and 8 MHz) at each 200 seconds, and the second one transmits 80 frequencies at each 300 seconds (scanning from 1 to 20 MHz in a logaritmic scale) [Macdougall et al. 1995]. The CADI operation to at EACF started on 2009.