Can someone explain to me why with the standard 5 Pole 2.7 kHz filter the DSP FC = 1.6kHz ? Looking at the NORMed DSP for that filter the LO = 0.25 kHz and the HI = 2.7 kHz. So I would have thought that FC = (2.7 - 0.25) / 2 or 1.225 kHz say 1.2 kHz. Maybe my idea of what FC represents is wrong.. 73 Stewart G3RXQ