Hello, I've traced the 2.8 kHz filter response with Mike's software and i get a little "anomaly" i can't explain me. I've a *.bmp file (~825 kB) or a *.txt file (~2kB). How can i "show" this unexplained (for me!) anomaly? I don't find a file upload procedure for this group. Thank you for your help. 73 QRO fr Rudolf, HB9ARI