You cannot prevent dupes. Just work them again, leave the QSO in your log and move on. John KK9A To: rtty at contesting.com Subject: Re: [RTTY] N1MM problems again From: Lee Roberts <ham at n0sq.us> Date: Sat, 11 Feb 2017 17:46:40 -0700 I got the serial number problem fixed. I need to figure out how to prevent dupes now.