From 113f1770fff3dc72ea37ec44ce635babd9f069c8 Mon Sep 17 00:00:00 2001
From: Joe Taylor <k1jt@arrl.org>
Date: Tue, 27 Nov 2012 16:48:50 +0000
Subject: [PATCH] Better way of estimating noise level for S/N measurements.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@2776 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
---
 lib/decode9a.f90 |  2 +-
 lib/downsam9.f90 | 26 +++++++++++++++++++-------
 lib/jt9sim.f90   |  8 +++++---
 lib/symspec2.f90 | 10 +++++++---
 mainwindow.cpp   |  2 +-
 5 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/lib/decode9a.f90 b/lib/decode9a.f90
index f3bddf6cc..056b9137d 100644
--- a/lib/decode9a.f90
+++ b/lib/decode9a.f90
@@ -16,7 +16,7 @@ subroutine decode9a(c0,npts8,nsps8,fpk,syncpk,snrdb,xdt,freq,drift,   &
   ndown=nsps8/nspsd
 
 ! Downsample to 16 samples/symbol
-  call downsam9(c0,npts8,nsps8,nspsd,fpk,c2,nz2) 
+  call downsam9(c0,npts8,nsps8,nspsd,fpk,c2,nz2)
 
   call peakdt9(c2,nz2,nsps8,nspsd,c3,nz3,xdt)
 
diff --git a/lib/downsam9.f90 b/lib/downsam9.f90
index 4570d731c..21b216824 100644
--- a/lib/downsam9.f90
+++ b/lib/downsam9.f90
@@ -6,6 +6,7 @@ subroutine downsam9(c0,npts8,nsps8,nspsd,fpk,c2,nz2)
   complex c0(0:npts8-1)
   complex c1(0:NMAX-1)
   complex c2(0:4096-1)
+  real s(1000)
 
   fac=1.e-4
   c1(0:npts8-1)=fac*c0                     !Copy c0 into c1
@@ -18,12 +19,22 @@ subroutine downsam9(c0,npts8,nsps8,nspsd,fpk,c2,nz2)
   df1=1500.0/nfft1
   call four2a(c1,nfft1,1,-1,1)             !Forward FFT
 
-!  do i=0,nfft1-1
-!     f=i*df1
-!     pp=real(c1(i))**2 + aimag(c1(i))**2
-!     write(50,3009) i,f,1.e-6*pp
-!3009 format(i8,f12.3,f12.3)
-!  enddo   
+  ia=nint(250.0/df1)
+  nadd=1.0/df1
+  j=250/df1
+  s=0.
+  do i=1,1000
+     do n=1,nadd
+        j=j+1
+        s(i)=s(i)+real(c1(j))**2 + aimag(c1(j))**2
+     enddo
+!     write(50,3000) i,(j-nadd/2)*df1,s(i)
+!3000 format(i5,2f12.3)
+  enddo
+  call pctile(s,1000,40,avenoise)
+!  write(71,*) avenoise,nadd
+!  call flush(50)
+!  call flush(71)
   
   ndown=nsps8/16                           !Downsample factor
   nfft2=nfft1/ndown                        !Backward FFT length
@@ -31,10 +42,11 @@ subroutine downsam9(c0,npts8,nsps8,nspsd,fpk,c2,nz2)
    
   fshift=fpk-1500.0
   i0=nh1 + fshift/df1
+  fac=1.0/avenoise
   do i=0,nfft2-1
      j=i0+i
      if(i.gt.nh2) j=j-nfft2
-     c2(i)=c1(j)
+     c2(i)=fac*c1(j)
   enddo
 
   call four2a(c2,nfft2,1,1,1)              !Backward FFT
diff --git a/lib/jt9sim.f90 b/lib/jt9sim.f90
index 3875a5668..c1bf1171a 100644
--- a/lib/jt9sim.f90
+++ b/lib/jt9sim.f90
@@ -102,7 +102,8 @@ program jt9sim
 
         f=f0
         if(nsigs.gt.1) f=f0 - 0.5d0*fspan + fspan*(isig-1.d0)/(nsigs-1.d0)
-        snrdbx=snrdb
+        snrdbx=snrdb 
+!        snrdbx=snrdb + (ifile-1)*4.0
         sig=10.0**(0.05*snrdbx)
         write(*,1020) ifile,isig,f,snrdbx,msgsent
 1020    format(i3,i4,f10.3,f7.1,2x,a22)
@@ -110,8 +111,9 @@ program jt9sim
         phi=0.
         baud=12000.d0/nsps
         k=12000                             !Start audio at t = 1.0 s
-        f1=0.0001 * (ifile-1)
-        print*,ifile-2,f1
+!        f1=0.0001 * (ifile-1)
+        f1=0.
+!        print*,ifile-1,f1
         dphi2=0.
         ddphi2=twopi*f1*dt/60.0
         do isym=1,85
diff --git a/lib/symspec2.f90 b/lib/symspec2.f90
index bb9d3a804..70afb79ee 100644
--- a/lib/symspec2.f90
+++ b/lib/symspec2.f90
@@ -49,9 +49,13 @@ subroutine symspec2(c5,nz3,nsps8,nspsd,fsample,snrdb,i1SoftSymbolsScrambled)
 
   sig=sig/69.
   df8=1500.0/nsps8
-  t=max(1.0,sig/xmed - 1.0)
-  snrdb=db(t) - db(2500.0/df8) - 4.5
-!  print*,'A',ave,xmed,sig,t,df8,snrdb
+!  t=max(1.0,sig/xmed - 1.0)
+!  snrdb=db(t) - db(2500.0/df8) - 4.5
+  t=max(1.0,sig - 1.0)
+  snrdb=db(t) - 60.3
+!  write(71,3001) ave,xmed,sig,db(sig),t,snrdb
+!3001 format(6f12.2)
+!  call flush(71)
      
   m0=3
   k=0
diff --git a/mainwindow.cpp b/mainwindow.cpp
index b1642789c..04b7626f6 100644
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -1,4 +1,4 @@
-//-------------------------------------------------------------- MainWindow
+//--------------------------------------------------------------- MainWindow
 #include "mainwindow.h"
 #include "ui_mainwindow.h"
 #include "devsetup.h"