I thought that the 6 plus (564) had a TXCO and the older (563) had a crystal oven. Did Ten Tec make that change with the option 3 upgrade? 73 de Bill N2WF Bill Nicolson - N2WF - K2 #1764 Colonia - New Jersey E-Mail - n2wf@arrl.net Web - http://www.qsl.net/n2wf