There is a nice article by PA3CW for a 600 meter amplifier at <http://www.elecraft.com/TechNotes/k3qtx_v2_pa3cw.pdf>It was designed as an amplifier for the Elecraft K3.Another great one is from John, KB5NJD/XIQ, His Amplifier is described at<http://njdtechnologies.net/630-meter-class-de-amplifier/ >Paul w0rw