From 8d21cdf1c70fde62ef9a98b70ccda4e0daedf765 Mon Sep 17 00:00:00 2001
From: Joe Taylor <k1jt@arrl.org>
Date: Tue, 15 Mar 2016 20:44:03 +0000
Subject: [PATCH] Change Doppler spread to Lorentzian shape with cutoff at x=3.
  Several tweaks to output format from fer65.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6534 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
---
 lib/fer65.f90   |  8 +++++---
 lib/jt65sim.f90 | 12 +++++++-----
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/lib/fer65.f90 b/lib/fer65.f90
index 0dbe1c1a0..62d36838a 100644
--- a/lib/fer65.f90
+++ b/lib/fer65.f90
@@ -50,10 +50,11 @@ program fer65
   open(20,file='fer65.20',status='unknown')
   open(21,file='fer65.21',status='unknown')
 
-  write(20,1000) iters,ntrials,naggressive,d
-1000 format('Iters:',i6,'   T:',i7,'   Aggressive:',i3,'   Doppler:',f6.1)
+  write(20,1000) submode,iters,ntrials,naggressive,d
+1000 format('JT65',a1,'   Iters:',i6,'   T:',i7,'   Aggressive:',i3,   &
+          '   Doppler:',f6.1)
   write(20,1002) 
-1002 format('  dB  nsync ngood nbad    sync       snr         ',    &
+1002 format(/'  dB  nsync ngood nbad     sync       dsnr        ',     &
             'DT        Freq       Drift'/77('-'))
 
   do isnr=0,20
@@ -138,6 +139,7 @@ program fer65
      endif
 
      dsnr=xsnr-snr
+     if(ngood.eq.0) dsnr=0.
      write(20,1100) snr,nsync,ngood,nbad,xsync,esync,dsnr,esnr,  &
           xdt,edt,xfreq,efreq,xdrift,edrift
 1100 format(f5.1,2i6i4,2f6.1,f6.1,f5.1,f6.2,f5.2,f7.1,3f5.1)
diff --git a/lib/jt65sim.f90 b/lib/jt65sim.f90
index d94695253..bca8793fd 100644
--- a/lib/jt65sim.f90
+++ b/lib/jt65sim.f90
@@ -200,18 +200,20 @@ program jt65sim
         cspread(0)=1.0
         cspread(NH)=0.
 
-! The following statement was added 3/15/2016 to make the half-power tone 
+! The following options were added 3/15/2016 to make the half-power tone 
 ! widths equal to the requested Doppler spread.  (Previously we effectively 
-! used b=1.0, which made the tones 1.665 times wider.)
-        b=2.0*sqrt(log(2.0))
+! used b=1.0 and Gaussian shape, which made the tones 1.665 times wider.)
+!        b=2.0*sqrt(log(2.0))                          !Gaussian
+        b=2.0                                         !Lorenzian
 
         do i=1,NH
            f=i*df
            x=b*f/fspread
            z=0.
            a=0.
-           if(x.lt.50.0) then
-              a=sqrt(exp(-x*x))
+           if(x.lt.3.0) then                          !Cutoff beyond x=3
+!              a=sqrt(exp(-x*x))                      !Gaussian
+              a=sqrt(1.0/(1.0+x*x))                   !Lorentzian
               call random_number(r1)
               phi1=twopi*r1
               z=a*cmplx(cos(phi1),sin(phi1))