Has anyone built this circuit? http://www.w1hkj.com/FldigiHelp-3.21/PseudoFSK.html I'm thinking this would be a good alternative to using the tiny modem described here earlier. I see in the 2-Tone documentation that you should use .1uF caps for the filter caps because 2-Tone uses 5 KHz tone instead of 1 KHz as shown in the link. 73 Jim W7RY