here is the basic circuit that I found  online. You may be able to adapt it
to your needs.  or use some switching to put it in and out of line as needed
Sine wave oscillator . Hope this at least gets you started in the right
direction

Eddie Turner, kc4awz

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics