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More code cleanup -- just comments and formatting.
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@ -3,6 +3,7 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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use packjt77
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include 'ft4_params.f90'
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parameter (NSS=NSPS/NDOWN)
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character message*37
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character c77*77
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character*61 line
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@ -13,7 +14,7 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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complex cd2(0:NMAX/NDOWN-1) !Complex waveform
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complex cb(0:NMAX/NDOWN-1)
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complex cd(0:NN*NSS-1) !Complex waveform
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complex cd(0:NN*NSS-1) !Complex waveform
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complex ctwk(4*NSS),ctwk2(4*NSS)
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complex csymb(NSS)
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complex cs(0:3,NN)
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@ -26,6 +27,7 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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real s2(0:255)
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real candidate(3,100)
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real savg(NH1),sbase(NH1)
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integer icos4(0:3)
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integer*2 iwave(NMAX) !Generated full-length waveform
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integer*1 message77(77),apmask(2*ND),cw(2*ND)
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@ -35,16 +37,17 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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logical unpk77_success
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logical one(0:255,0:7) ! 256 4-symbol sequences, 8 bits
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logical first
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data icos4/0,1,3,2/
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data graymap/0,1,3,2/
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data first/.true./
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save one
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save one,first
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hhmmss=cdatetime0(8:13)
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fs=12000.0/NDOWN !Sample rate
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dt=1/fs !Sample interval after downsample (s)
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tt=NSPS*dt !Duration of "itone" symbols (s)
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txt=NZ*dt !Transmission length (s)
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fs=12000.0/NDOWN !Sample rate after downsampling
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dt=1/fs !Sample interval after downsample (s)
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tt=NSPS*dt !Duration of "itone" symbols (s)
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txt=NZ*dt !Transmission length (s) without ramp up/down
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twopi=8.0*atan(1.0)
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h=1.0
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@ -58,30 +61,29 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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first=.false.
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endif
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data_dir="."
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fMHz=7.074
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candidate=0.0
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ncand=0
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fa=400.0
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fb=3000.0
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syncmin=1.2
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maxcand=100
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! call syncft4(iwave,nfa,nfb,syncmin,nfqso,maxcand,s,candidate,ncand,sbase)
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call getcandidates4(iwave,fa,fb,syncmin,nfqso,100,savg,candidate,ncand,sbase)
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! These are temporary. Correct values should be passed in as arguments.
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data_dir="."
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fMHz=7.074
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fa=400.0
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fb=3000.0
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call getcandidates4(iwave,fa,fb,syncmin,nfqso,maxcand,savg,candidate, &
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ncand,sbase)
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ndecodes=0
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do icand=1,ncand
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f0=candidate(1,icand)
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xsnr=10*log10(candidate(3,icand))-18.0
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if( f0.le.375.0 .or. f0.ge.(5000.0-375.0) ) cycle
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call ft4_downsample(iwave,f0,cd2) ! downsample from 512 Sa/Symbol to 32 Sa/Symbol
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if( f0.le.375.0 .or. f0.ge.(5000.0-375.0) ) cycle !### TBD? ###
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call ft4_downsample(iwave,f0,cd2) !Downsample to 32 Samples/Symbol
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sum2=sum(cd2*conjg(cd2))/(20.0*76)
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if(sum2.gt.0.0) cd2=cd2/sqrt(sum2)
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! 750 samples/second here
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! Sample rate is now 12000/16 = 750 samples/second
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do isync=1,2
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if(isync.eq.1) then
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idfmin=-50
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@ -107,7 +109,7 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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ctwk=1.
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call twkfreq1(ctwk,4*NSS,fs,a,ctwk2)
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do istart=ibmin,ibmax,ibstp
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call sync4d(cd2,istart,ctwk2,1,sync)
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call sync4d(cd2,istart,ctwk2,1,sync) !Find sync power
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if(sync.gt.smax) then
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smax=sync
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ibest=istart
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@ -118,7 +120,7 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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enddo
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f0=f0+real(idfbest)
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call ft4_downsample(iwave,f0,cb) ! downsample from 320s/Symbol to 20s/Symbol
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call ft4_downsample(iwave,f0,cb) !Final downsample with corrected f0
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sum2=sum(abs(cb)**2)/(real(NSS)*NN)
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if(sum2.gt.0.0) cb=cb/sqrt(sum2)
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cd=cb(ibest:ibest+NN*NSS-1)
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@ -130,7 +132,7 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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s4(0:3,k)=abs(csymb(1:4))
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enddo
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! sync quality check
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! Sync quality check
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is1=0
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is2=0
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is3=0
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@ -145,10 +147,9 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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ip=maxloc(s4(:,k+99))
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if(icos4(k-1).eq.(ip(1)-1)) is4=is4+1
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enddo
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! hard sync sum - max is 16
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nsync=is1+is2+is3+is4
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nsync=is1+is2+is3+is4 !Number of hard sync errors, 0-16
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do nseq=1,3
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do nseq=1,3 !Try coherent sequences of 1, 2, and 4 symbols
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if(nseq.eq.1) nsym=1
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if(nseq.eq.2) nsym=2
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if(nseq.eq.3) nsym=4
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@ -233,7 +234,8 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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llr2=llr
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if(ibias.eq.1) llr2=llr+0.4
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if(ibias.eq.2) llr2=llr-0.4
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call bpdecode174_91(llr2,apmask,max_iterations,message77,cw,nharderror,niterations)
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call bpdecode174_91(llr2,apmask,max_iterations,message77, &
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cw,nharderror,niterations)
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if(nharderror.ge.0) exit
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enddo
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if(sum(message77).eq.0) cycle
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@ -256,11 +258,12 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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write(24,1002) cdatetime0,nsnr,ibest/750.0,nint(freq),message, &
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nharderror,nsync_qual,isd,niterations
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if(hhmmss.eq.' ') write(*,1002) cdatetime0,nsnr, &
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ibest/750.0,nint(freq),message,nharderror,nsync_qual,isd,niterations
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ibest/750.0,nint(freq),message,nharderror,nsync_qual,isd, &
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niterations
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1002 format(a17,i4,f6.2,i5,' Rx ',a37,4i5)
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close(24)
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!### Temporary: assume most recent decoded message conveys "hiscall".
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!### Temporary: assume most recent decoded message conveys "hiscall". ###
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i0=index(message,' ')
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if(i0.ge.3 .and. i0.le.7) then
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hiscall=message(i0+1:i0+6)
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@ -279,8 +282,8 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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exit
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endif
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enddo ! sequence estimation
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enddo !candidate list
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enddo !Sequence estimation
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enddo !Candidate list
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return
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end subroutine ft4_decode
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@ -317,6 +320,7 @@ subroutine ft4_downsample(iwave,f0,c)
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c1=c1/NFFT2
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call four2a(c1,NFFT2,1,1,1) !c2c FFT back to time domain
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c=c1(0:NMAX/NDOWN-1)
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return
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end subroutine ft4_downsample
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@ -1,12 +1,14 @@
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! FT4
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! LDPC (174,91) code
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! LDPC(174,91) code, four 4x4 Costas arrays for Sync
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parameter (KK=91) !Information bits (77 + CRC14)
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parameter (ND=87) !Data symbols
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parameter (NS=16) !Sync symbols
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parameter (NN=NS+ND) !Total channel symbols (103)
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parameter (NN=NS+ND) !Sync and data symbols (103)
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parameter (NN2=NS+ND+2) !Total channel symbols (105)
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parameter (NSPS=512) !Samples per symbol at 12000 S/s
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parameter (NZ=NSPS*NN) !Samples in full 4.395 s message frame (52736)
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parameter (NZ=NSPS*NN) !Sync and Data samples (52736)
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parameter (NZ2=NSPS*NN2) !Total samples in shaped waveform (53760)
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parameter (NMAX=5.0*12000) !Samples in iwave (60,000)
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parameter (NFFT1=2048, NH1=NFFT1/2) !Length of FFTs for symbol spectra
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parameter (NSTEP=NSPS/4) !Coarse time-sync step size
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