From 2a0602b19dad78f7d47fd90b9c2c118624b02e5a Mon Sep 17 00:00:00 2001
From: Joe Taylor <k1jt@arrl.org>
Date: Mon, 23 Nov 2015 18:20:55 +0000
Subject: [PATCH] Add degrade_snr.f90

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6167 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
---
 lib/degrade_snr.f90 | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 lib/degrade_snr.f90

diff --git a/lib/degrade_snr.f90 b/lib/degrade_snr.f90
new file mode 100644
index 000000000..8e6efb35a
--- /dev/null
+++ b/lib/degrade_snr.f90
@@ -0,0 +1,20 @@
+subroutine degrade_snr(d2,npts,db)
+
+  integer*2 d2(npts)
+  real dat(60*12000)
+
+  dat(1:npts)=d2
+  p0=dot_product(dat(1:npts),dat(1:npts))/npts
+  s=sqrt(p0*(10.0**(0.1*db) - 1.0))
+  do i=1,npts
+     d2(i)=nint(dat(i) + s*gran())
+  enddo
+  
+!  dat(1:npts)=d2
+!  p1=dot_product(dat(1:npts),dat(1:npts))/npts
+!  print*,db,p0,s,10.0*log10(p1/p0)
+
+  return
+end subroutine degrade_snr
+
+