Correct the FT8 downsample factor to be exactly 1/64.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7779 ab8295b8-cf94-4d9e-aec4-7959e3be5d79

lib/fsk4hf/ft8b.f90

@@ -13,7 +13,7 @@ subroutine ft8b(dd0,nfqso,f1,xdt,nharderrors,dmin,nbadcrc,message,xsnr)
   integer*1 decoded(KK),apmask(3*ND),cw(3*ND)
   integer itone(NN)
   integer icos7(0:6)
-  complex cd0(NP2) 
+  complex cd0(3125)
   complex csync(0:6,32)
   complex ctwk(32)
   complex csymb(32)
@@ -193,30 +193,34 @@ subroutine ft8_downsample(dd,f0,c1)
 
 ! Downconvert to complex data sampled at 187.5 Hz, 32 samples/symbol
 
-  parameter (NMAX=15*12000,NFFT2=2812)
+  parameter (NMAX=15*12000)
+  parameter (NFFT1=200000,NFFT2=3125)      !200000/64 = 3125
   complex c1(0:NFFT2-1)
-  complex cx(0:NMAX/2)
-  real dd(NMAX),x(NMAX)
+  complex cx(0:NFFT1/2)
+  real dd(NMAX),x(NFFT1)
   equivalence (x,cx)
   save x
 
-  df=12000.0/NMAX
-  x=dd
-  call four2a(cx,NMAX,1,-1,0)             !r2c FFT to freq domain
-  baud=12000.0/(32.0*64.0)
+  df=12000.0/NFFT1
+  x(1:NMAX)=dd
+  x(NMAX+1:NFFT1)=0.                       !Zero-pad the x array
+  call four2a(cx,NFFT1,1,-1,0)             !r2c FFT to freq domain
+  baud=12000.0/2048.0
   i0=nint(f0/df)
   ft=f0+8.0*baud
-  it=min(nint(ft/df),NMAX/2-1)
+  it=min(nint(ft/df),NFFT1/2)
   fb=f0-1.0*baud
   ib=max(1,nint(fb/df))
   k=0
-  c1=cmplx(0.0,0.0)
+  c1=0.
   do i=ib,it
    c1(k)=cx(i)
    k=k+1
   enddo
   c1=cshift(c1,i0-ib)
   call four2a(c1,NFFT2,1,1,1)            !c2c FFT back to time domain
-  c1=c1/(NMAX*NFFT2)
+  fac=1.0/sqrt(float(NFFT1)*NFFT2)
+  c1=fac*c1
+
   return
 end subroutine ft8_downsample

lib/refspectrum.f90

@@ -25,6 +25,8 @@ subroutine refspectrum(id2,id2b,kk,bclear,brefspec,buseref,fname)
   data first/.true./,blastuse/.false./
   save
 
+  print*,fname
+
   if(first) then
      pi=4.0*atan(1.0)
      do i=0,NFFT-1