The old linear LNBs for ExpressVu work really well on FTA -- I use them all the time with 30" dishes. The problem with using them on a B.U.D. is adjusting the skew. The advantage of using a KU band LNB made for a B.U.D. is the LNB is mounted on the feedhorn and the polarizer motor (used for the
C-band LNB) now also controls skew for the KU LNB.
Some brands of KU LNBs made for B.U.D.s are Chapparel or Norsat or Aspen Eagle.
kat