Ken, QST,June 2002,pgs 61/62, has a preamp circuit and analysis for the D104. Also see QST,Aug 1999, pg 34, QST,March 2001, pg 59. You might find this info online at the ARRL website. Jamie Danter/KF4VOP --- [Pre-scanned for viruses as a service provided by Internet America. Be sure you have your own virus protection software to catch viruses that get by this pre-scan.]