WSJT-X/short65.f

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subroutine short65(data,jz,NFreeze,MouseDF,DFTolerance,
+ mode65,nspecialbest,nstest,dfsh,iderrbest,idriftbest,
+ snrdb,ss1a,ss2a,nwsh,idfsh)
C Checks to see if this might be a shorthand message.
C This is done before zapping, downsampling, or normal decoding.
parameter (NP2=60*11025) !Size of data array
parameter (NFFT=16384) !FFT length
parameter (NH=NFFT/2) !Step size
parameter (MAXSTEPS=60*11025/NH) !Max # of steps
real data(jz)
integer DFTolerance
real s2(NH,MAXSTEPS) !2d spectrum
real ss(NH,4) !Save spectra in four phase bins
real psavg(NH)
real sigmax(4) !Peak of spectrum at each phase
real ss1a(-224:224) !Lower magenta curve
real ss2a(-224:224) !Upper magenta curve
real ss1(-473:1784) !Lower magenta curve (temp)
real ss2(-473:1784) !Upper magenta curve (temp)
real ssavg(-11:11)
integer ipk(4) !Peak bin at each phase
save
nspecialbest=0 !Default return value
nstest=0
df=11025.0/NFFT
C Do 16 k FFTs, stepped by 8k. (*** Maybe should step by 4k? ***)
call zero(psavg,NH)
nsteps=(jz-NH)/(4*NH)
nsteps=4*nsteps !Number of steps
do j=1,nsteps
k=(j-1)*NH + 1
call ps(data(k),NFFT,s2(1,j)) !Get power spectra
if(mode65.eq.4) then
call smooth(s2(1,j),NH)
call smooth(s2(1,j),NH)
endif
call add(psavg,s2(1,j),psavg,NH)
enddo
call flat1(psavg,s2,NH,nsteps,NH,MAXSTEPS)
nfac=40*mode65
dtstep=0.5/df
fac=dtstep/(60.0*df)
C Define range of frequencies to be searched
fa=max(200.0,1270.46+MouseDF-600.0)
fb=min(4800.0,1270.46+MouseDF+600.0)
ia=fa/df
ib=fb/df + 4.1*nfac !Upper tone is above sync tone by 4*nfac*df Hz
if(NFreeze.eq.1) then
fa=max(200.0,1270.46+MouseDF-DFTolerance)
fb=min(4800.0,1270.46+MouseDF+DFTolerance)
endif
ia2=fa/df
ib2=fb/df + 4.1*nfac !Upper tone is above sync tone by 4*nfac*df Hz
if(ib2.gt.NH) ib2=NH
C Find strongest line in each of the 4 phases, repeating for each drift rate.
sbest=0.
snrbest=0.
idz=6.0/df !Is this the right drift range?
do idrift=-idz,idz
drift=idrift*df*60.0/49.04
call zero(ss,4*NH) !Clear the accumulating array
do j=1,nsteps
n=mod(j-1,4)+1
k=nint((j-nsteps/2)*drift*fac) + ia
call add(ss(ia,n),s2(k,j),ss(ia,n),ib-ia+1)
enddo
do n=1,4
sigmax(n)=0.
do i=ia2,ib2
sig=ss(i,n)
if(sig.ge.sigmax(n)) then
ipk(n)=i
sigmax(n)=sig
if(sig.ge.sbest) then
sbest=sig
nbest=n
fdotsh=drift
endif
endif
enddo
enddo
n2best=nbest+2
if(n2best.gt.4) n2best=nbest-2
xdf=min(ipk(nbest),ipk(n2best))*df - 1270.46
if(NFreeze.eq.1 .and. abs(xdf-mousedf).gt.DFTolerance) goto 10
idiff=abs(ipk(nbest)-ipk(n2best))
xk=float(idiff)/nfac
k=nint(xk)
iderr=nint((xk-k)*nfac)
nspecial=0
maxerr=nint(0.008*abs(idiff) + 0.51)
if(abs(iderr).le.maxerr .and. k.ge.2 .and. k.le.4) nspecial=k
if(nspecial.gt.0) then
call getsnr(ss(ia2,nbest),ib2-ia2+1,snr1)
call getsnr(ss(ia2,n2best),ib2-ia2+1,snr2)
snr=0.5*(snr1+snr2)
if(snr.gt.snrbest) then
snrbest=snr
nspecialbest=nspecial
nstest=snr/2.0 - 2.0 !Threshold set here
if(nstest.lt.0) nstest=0
if(nstest.gt.10) nstest=10
dfsh=nint(xdf)
iderrbest=iderr
idriftbest=idrift
snrdb=db(snr) - db(2500.0/df) - db(sqrt(nsteps/4.0))+1.8
n1=nbest
n2=n2best
ipk1=ipk(n1)
ipk2=ipk(n2)
endif
endif
if(nstest.eq.0) nspecial=0
10 enddo
if(nstest.eq.0) nspecialbest=0
df4=4.0*df
if(nstest.gt.0) then
if(ipk1.gt.ipk2) then
ntmp=n1
n1=n2
n2=ntmp
ntmp=ipk1
ipk1=ipk2
ipk2=ntmp
endif
call zero(ss1,2258)
call zero(ss2,2258)
do i=ia2,ib2,4
f=df*i
k=nint((f-1270.46)/df4)
ss1(k)=0.3 * (ss(i-2,n1) + ss(i-1,n1) + ss(i,n1) +
+ ss(i+1,n1) + ss(i+2,n1))
ss2(k)=0.3 * (ss(i-2,n2) + ss(i-1,n2) + ss(i,n2) +
+ ss(i+1,n2) + ss(i+2,n2))
enddo
kpk1=nint(0.25*ipk1-472.0)
kpk2=kpk1 + nspecial*mode65*10
ssmax=0.
do i=-10,10
ssavg(i)=ss1(kpk1+i) + ss2(kpk2+i)
if(ssavg(i).gt.ssmax) then
ssmax=ssavg(i)
itop=i
endif
enddo
base=0.25*(ssavg(-10)+ssavg(-9)+ssavg(9)+ssavg(10))
shalf=0.5*(ssmax+base)
do k=1,8
if(ssavg(itop-k).lt.shalf) go to 110
enddo
k=8
110 x=(ssavg(itop-(k-1))-shalf)/(ssavg(itop-(k-1))-ssavg(itop-k))
do k=1,8
if(ssavg(itop+k).lt.shalf) go to 120
enddo
k=8
120 x=x+(ssavg(itop+(k-1))-shalf)/(ssavg(itop+(k-1))-ssavg(itop+k))
nwsh=nint(x*df4)
endif
C See if orange/magenta curves need to be shifted:
idfsh=0
if(mousedf.lt.-600) idfsh=-670
if(mousedf.gt.600) idfsh=1000
if(mousedf.gt.1600) idfsh=2000
if(mousedf.gt.2600) idfsh=3000
i0=nint(idfsh/df4)
do i=-224,224
ss1a(i)=ss1(i+i0)
ss2a(i)=ss2(i+i0)
enddo
return
end