........ > 6. There are RX ANT IN and OUT jacks on the back panel - what is the OUT > jack for - another receiver? "Yes, or adding a "field day filter" or ??? in line with the receiver." How about a K2 and make it an SO3R? Some of us long time K2 owners, esp. testers will want to hang onto the "old" rig for many reasons. Bill K9YEQ K2-35, KX1-35, etc., etc....