WSJT-X/lib/genjt9.f90

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Fortran
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subroutine genjt9(message,msgsent,d6)
! Encodes a JT9 message and returns msgsent, the message as it will
! be decoded, and an integer array d6(85) of 9-FSK tone values
! in the range 0-8.
character*22 message !Message to be generated
character*22 msgsent !Message as it will be received
integer*4 d0(13) !72-bit message as 6-bit words
integer*1 d1(13) !72 bits and zero tail as 8-bit bytes
integer*1 d2(207) !Encoded information-carrying bits
integer*1 d3(207) !Bits from d2, after interleaving
integer*4 d4(69) !Symbols from d3, values 0-7
integer*4 d5(69) !Gray-coded symbols, values 0-7
integer*4 d6(85) !Channel symbols including sync, values 0-8
integer isync(85) !Sync vector
data isync/ &
1,0,0,0,0,1,0,0,0,0,1,0,0,0,0,1,0,0,0,0, &
1,0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,1,0, &
0,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0, &
0,0,1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0, &
1,0,0,0,1/
save
call packmsg(message,d0) !Pack message into 12 6-bit bytes
call unpackmsg(d0,msgsent) !Unpack d0 to get msgsent
call entail(d0,d1) !Add tail, convert to 8-bit bytes
nsym2=206
call encode232(d1,nsym2,d2) !Convolutional code, K=32, r=1/2
call interleave9(d2,1,d3) !Interleave the single bits
call packbits(d3,nsym2,3,d4) !Pack 3-bit groups into words
! d5=d4
! print*,d5
call graycode(d4,69,1,d5) !Apply Gray code
! Insert sync symbols (ntone=0) and add 1 to the data-tone numbers.
j=0
do i=1,85
if(isync(i).eq.1) then
d6(i)=0
else
j=j+1
d6(i)=d5(j)+1
endif
enddo
return
end subroutine genjt9