subroutine ft8b(datetime,s,candidate,ncand) include 'ft8_params.f90' parameter(NRECENT=10) character*12 recent_calls(NRECENT) character message*22,datetime*13 real s(NH1,NHSYM) real s1(0:7,ND) real ps(0:7) real rxdata(3*ND),llr(3*ND) !Soft symbols real candidate(3,100) integer*1 decoded(KK),apmask(3*ND),cw(3*ND) max_iterations=40 norder=2 tstep=0.5*NSPS/12000.0 df=12000.0/NFFT1 do icand=1,ncand f1=candidate(1,icand) xdt=candidate(2,icand) sync=candidate(3,icand) i0=nint(f1/df) j0=nint(xdt/tstep) j=0 ia=i0 ib=i0+14 do k=1,NN if(k.le.7) cycle if(k.ge.37 .and. k.le.43) cycle if(k.gt.72) cycle n=j0+2*(k-1)+1 if(n.lt.1) cycle j=j+1 s1(0:7,j)=s(ia:ib:2,n) enddo do j=1,ND ps=s1(0:7,j) where (ps.gt.0.0) ps=log(ps) r1=max(ps(1),ps(3),ps(5),ps(7))-max(ps(0),ps(2),ps(4),ps(6)) r2=max(ps(2),ps(3),ps(6),ps(7))-max(ps(0),ps(1),ps(4),ps(5)) r4=max(ps(4),ps(5),ps(6),ps(7))-max(ps(0),ps(1),ps(2),ps(3)) rxdata(3*j-2)=r4 rxdata(3*j-1)=r2 rxdata(3*j)=r1 enddo rxav=sum(rxdata)/(3.0*ND) rx2av=sum(rxdata*rxdata)/(3.0*ND) var=rx2av-rxav*rxav if( var .gt. 0.0 ) then rxsig=sqrt(var) else rxsig=sqrt(rx2av) endif rxdata=rxdata/rxsig ss=0.84 llr=2.0*rxdata/(ss*ss) apmask=0 cw=0 ! cw will be needed for subtraction. ! dmin is the correlation discrepancy of a returned codeword - it is ! used to select the best codeword within osd174. call bpdecode174(llr,apmask,max_iterations,decoded,cw,nharderrors) dmin=0.0 if(nharderrors.lt.0) then call osd174(llr,norder,decoded,cw,nharderrors,dmin) ! This threshold needs to be tuned. 99.0 should pass everything. if( dmin .gt. 99.0 ) nharderrors=-1 endif ! Reject the all-zero codeword if( count(cw.eq.0) .eq. 174 ) cycle nbadcrc=1 if( nharderrors .ge. 0 ) call chkcrc12a(decoded,nbadcrc) message=' ' if(nbadcrc.eq.0) then call extractmessage174(decoded,message,ncrcflag,recent_calls,nrecent) nsnr=nint(10.0*log10(sync) - 25.5) !### empirical ### write(*,1112) datetime(8:13),nsnr,xdt,nint(f1),message 1112 format(a6,i4,f5.1,i5," ~ ",a22) endif write(13,1110) datetime,0,nsnr,xdt,f1,xdta,f1a, & nharderrors,dmin,message 1110 format(a13,2i4,2(f6.2,f7.1),i4,' ~ ',f6.2,2x,a22) enddo return end subroutine ft8b