>It is my understanding that removing C180 IS the filter flattening >mod. The 120 pf cap that is added is only switched in when the OPT1 >filter is selected (always for TX and when OPT1 is used for RX). Right? I believe the actual SSB filter flattening mod is the 120pF cap... Removing C180 helps to flatten the filter response in BOTH modes. Tom N0SS