From 37591989829f0558c3d0cf693fa7e27cd663a01f Mon Sep 17 00:00:00 2001
From: Steve Franke <s.j.franke@icloud.com>
Date: Mon, 25 Feb 2019 15:03:43 -0600
Subject: [PATCH] Remove ramp-up and ramp-down symbols. Instead, shape the
 first 1/8th of first and last real symbols.

---
 lib/ft8/ft8sim_gfsk.f90 |  2 +-
 lib/ft8/gen_ft8wave.f90 | 30 +++++++++++++++++-------------
 widgets/mainwindow.cpp  |  2 +-
 3 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/lib/ft8/ft8sim_gfsk.f90 b/lib/ft8/ft8sim_gfsk.f90
index c40ffb2fa..aba046cef 100644
--- a/lib/ft8/ft8sim_gfsk.f90
+++ b/lib/ft8/ft8sim_gfsk.f90
@@ -6,7 +6,7 @@ program ft8sim_gfsk
   use wavhdr
   use packjt77
   include 'ft8_params.f90'               !Set various constants
-  parameter (NWAVE=(NN+2)*NSPS)
+  parameter (NWAVE=NN*NSPS)
   type(hdr) h                            !Header for .wav file
   character arg*12,fname*17
   character msg37*37,msgsent37*37
diff --git a/lib/ft8/gen_ft8wave.f90 b/lib/ft8/gen_ft8wave.f90
index f9665ca56..d4b58a426 100644
--- a/lib/ft8/gen_ft8wave.f90
+++ b/lib/ft8/gen_ft8wave.f90
@@ -27,7 +27,7 @@ subroutine gen_ft8wave(itone,nsym,nsps,fsample,f0,cwave,wave,icmplx,nwave)
   endif
 
 ! Compute the smoothed frequency waveform.
-! Length = (nsym+2)*nsps samples, zero-padded
+! Length = (nsym+2)*nsps samples, first and last symbols extended 
   dphi_peak=twopi*hmod/real(nsps)
   dphi=0.0 
   do j=1,nsym         
@@ -35,13 +35,16 @@ subroutine gen_ft8wave(itone,nsym,nsps,fsample,f0,cwave,wave,icmplx,nwave)
      ie=ib+3*nsps-1
      dphi(ib:ie) = dphi(ib:ie) + dphi_peak*pulse(1:3*nsps)*itone(j)
   enddo
+! Add dummy symbols at beginning and end with tone values equal to 1st and last symbol, respectively
+  dphi(0:2*nsps-1)=dphi(0:2*nsps-1)+dphi_peak*itone(1)*pulse(nsps+1:3*nsps)
+  dphi(nsym*nsps:(nsym+2)*nsps-1)=dphi(nsym*nsps:(nsym+2)*nsps-1)+dphi_peak*itone(nsym)*pulse(1:2*nsps)
 
 ! Calculate and insert the audio waveform
   phi=0.0
   dphi = dphi + twopi*f0*dt                          !Shift frequency up by f0
   wave=0.
   k=0
-  do j=0,nwave-1
+  do j=nsps,nsps+nwave-1                             !Don't include dummy symbols
      k=k+1
      if(icmplx.eq.0) then
         wave(k)=sin(phi)
@@ -51,19 +54,20 @@ subroutine gen_ft8wave(itone,nsym,nsps,fsample,f0,cwave,wave,icmplx,nwave)
      phi=mod(phi+dphi(j),twopi)
   enddo
 
-! Compute the ramp-up and ramp-down symbols
+! Apply envelope shaping to the first and last symbols
+  nramp=nint(nsps/8.0)
   if(icmplx.eq.0) then
-     wave(1:nsps)=wave(1:nsps) *                                          &
-          (1.0-cos(twopi*(/(i,i=0,nsps-1)/)/(2.0*nsps)))/2.0
-     k1=(nsym+1)*nsps+1
-     wave(k1:k1+nsps-1)=wave(k1:k1+nsps-1) *                              &
-          (1.0+cos(twopi*(/(i,i=0,nsps-1)/)/(2.0*nsps)))/2.0
+     wave(1:nramp)=wave(1:nramp) *                                          &
+          (1.0-cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
+     k1=nsym*nsps-nramp+1
+     wave(k1:k1+nramp-1)=wave(k1:k1+nramp-1) *                              &
+          (1.0+cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
   else
-     cwave(1:nsps)=cwave(1:nsps) *                                        &
-          (1.0-cos(twopi*(/(i,i=0,nsps-1)/)/(2.0*nsps)))/2.0
-     k1=(nsym+1)*nsps+1
-     cwave(k1:k1+nsps-1)=cwave(k1:k1+nsps-1) *                            &
-          (1.0+cos(twopi*(/(i,i=0,nsps-1)/)/(2.0*nsps)))/2.0
+     cwave(1:nramp)=cwave(1:nramp) *                                        &
+          (1.0-cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
+     k1=nsym*nsps-nramp+1
+     cwave(k1:k1+nramp-1)=cwave(k1:k1+nramp-1) *                            &
+          (1.0+cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
   endif
 
   return
diff --git a/widgets/mainwindow.cpp b/widgets/mainwindow.cpp
index 78b70229a..62af345da 100644
--- a/widgets/mainwindow.cpp
+++ b/widgets/mainwindow.cpp
@@ -6871,7 +6871,7 @@ void MainWindow::transmit (double snr)
     float fsample=48000.0;
     float f0=ui->TxFreqSpinBox->value() - m_XIT;
     int icmplx=0;
-    int nwave=(nsym+2)*nsps;
+    int nwave=nsym*nsps;
     gen_ft8wave_(const_cast<int *>(itone),&nsym,&nsps,&fsample,&f0,foxcom_.wave,
                  foxcom_.wave,&icmplx,&nwave);