      subroutine dradb2 (ido,l1,cc,ch,wa1)
      double precision cc(ido,2,l1), ch(ido,l1,2), wa1(1), ti2, tr2
c
      do 101 k=1,l1
         ch(1,k,1) = cc(1,1,k)+cc(ido,2,k)
         ch(1,k,2) = cc(1,1,k)-cc(ido,2,k)
  101 continue
c
      if (ido-2) 107,105,102
  102 idp2 = ido+2
      do 104 k=1,l1
         do 103 i=3,ido,2
            ic = idp2-i
            ch(i-1,k,1) = cc(i-1,1,k)+cc(ic-1,2,k)
            tr2 = cc(i-1,1,k)-cc(ic-1,2,k)
            ch(i,k,1) = cc(i,1,k)-cc(ic,2,k)
            ti2 = cc(i,1,k)+cc(ic,2,k)
            ch(i-1,k,2) = wa1(i-2)*tr2-wa1(i-1)*ti2
            ch(i,k,2) = wa1(i-2)*ti2+wa1(i-1)*tr2
  103    continue
  104 continue
c
      if (mod(ido,2) .eq. 1) return
  105 do 106 k=1,l1
         ch(ido,k,1) = cc(ido,1,k)+cc(ido,1,k)
         ch(ido,k,2) = -(cc(1,2,k)+cc(1,2,k))
  106 continue
c
  107 return
      end