subroutine gen9(msg0,ichk,msgsent,i4tone,itype)

! Encodes a JT9 message and returns msgsent, the message as it will
! be decoded, and an integer array i4tone(85) of 9-FSK tone values 
! in the range 0-8.  

  use packjt
  character*22 msg0
  character*22 message                    !Message to be generated
  character*22 msgsent                    !Message as it will be received
  integer*4 i4Msg6BitWords(13)            !72-bit message as 6-bit words
  integer*1 i1Msg8BitBytes(13)            !72 bits and zero tail as 8-bit bytes
  integer*1 i1EncodedBits(207)            !Encoded information-carrying bits
  integer*1 i1ScrambledBits(207)          !Encoded bits after interleaving
  integer*4 i4DataSymbols(69)             !Data symbols (values 0-7)
  integer*4 i4GrayCodedSymbols(69)        !Gray-coded symbols (values 0-7)
  integer*4 i4tone(85)                    !Tone #s, data and sync (values 0-8)
  include 'jt9sync.f90'
  save

  if(msg0(1:1).eq.'@') then
     read(msg0(2:5),*,end=1,err=1) nfreq
     go to 2
1    nfreq=1000
2    i4tone(1)=nfreq
  else
     message=msg0
     do i=1,22
        if(ichar(message(i:i)).eq.0) then
           message(i:)='                      '
           exit
        endif
     enddo

     do i=1,22                               !Strip leading blanks
        if(message(1:1).ne.' ') exit
        message=message(i+1:)
     enddo

     call packmsg(message,i4Msg6BitWords,itype) !Pack into 12 6-bit bytes
     call unpackmsg(i4Msg6BitWords,msgsent) !Unpack to get msgsent
     if(ichk.ne.0) go to 999
     call entail(i4Msg6BitWords,i1Msg8BitBytes)  !Add tail, make 8-bit bytes
     nsym2=206
     call encode232(i1Msg8BitBytes,nsym2,i1EncodedBits)   !Encode K=32, r=1/2
     i1EncodedBits(207)=0
     call interleave9(i1EncodedBits,1,i1ScrambledBits)    !Interleave bits
     i1ScrambledBits(207)=0
     call packbits(i1ScrambledBits,69,3,i4DataSymbols)    !Pk 3-bits into words
     call graycode(i4DataSymbols,69,1,i4GrayCodedSymbols) !Apply Gray code

! Insert sync symbols at ntone=0 and add 1 to the data-tone numbers.
     j=0
     do i=1,85
        if(isync(i).eq.1) then
           i4tone(i)=0
        else
           j=j+1
           i4tone(i)=i4GrayCodedSymbols(j)+1
        endif
     enddo
  endif

999 return
end subroutine gen9