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FT8: Use GFSK waveform with BT=4.0 as reference for subtraction, for now. May want to change to BT=2.0 before v2.1 release?

This commit is contained in:
Steve Franke 2019-04-12 17:11:26 -05:00
parent 56c1aacbc2
commit cd8ea16f40
4 changed files with 20 additions and 13 deletions
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3
lib/ft8/ft8sim_gfsk.f90
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@ -57,6 +57,7 @@ program ft8sim_gfsk
baud=1.0/tt !Keying rate (baud)
bw=8*baud !Occupied bandwidth (Hz)
txt=NZ*dt !Transmission length (s)
bt=2.0
bandwidth_ratio=2500.0/(fs/2.0)
sig=sqrt(2*bandwidth_ratio) * 10.0**(0.05*snrdb)
if(snrdb.gt.90.0) sig=1.0
@ -67,7 +68,7 @@ program ft8sim_gfsk
n3=-1
call pack77(msg37,i3,n3,c77)
call genft8(msg37,i3,n3,msgsent37,msgbits,itone)
call gen_ft8wave(itone,NN,NSPS,fs,f0,cwave,xjunk,1,NWAVE) !Generate complex cwave
call gen_ft8wave(itone,NN,NSPS,bt,fs,f0,cwave,xjunk,1,NWAVE) !Generate complex cwave
write(*,*)
write(*,'(a23,a37,3x,a7,i1,a1,i1)') 'New Style FT8 Message: ',msgsent37,'i3.n3: ',i3,'.',n3

13
lib/ft8/gen_ft8wave.f90
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@ -1,4 +1,4 @@
subroutine gen_ft8wave(itone,nsym,nsps,fsample,f0,cwave,wave,icmplx,nwave)
subroutine gen_ft8wave(itone,nsym,nsps,bt,fsample,f0,cwave,wave,icmplx,nwave)
!
! generate ft8 waveform using Gaussian-filtered frequency pulses.
!
@ -9,21 +9,20 @@ subroutine gen_ft8wave(itone,nsym,nsps,fsample,f0,cwave,wave,icmplx,nwave)
real pulse(23040)
real dphi(0:(nsym+2)*nsps-1)
integer itone(nsym)
logical first
data first/.true./
save pulse,first,twopi,dt,hmod
data first/.true./,ibt0/0/
save pulse,twopi,dt,hmod,ibt0
if(first) then
ibt=nint(10*bt)
if(ibt0.ne.ibt) then
twopi=8.0*atan(1.0)
dt=1.0/fsample
hmod=1.0
bt=2.0
! Compute the frequency-smoothing pulse
do i=1,3*nsps
tt=(i-1.5*nsps)/real(nsps)
pulse(i)=gfsk_pulse(bt,tt)
enddo
first=.false.
ibt0=nint(10*bt)
endif
! Compute the smoothed frequency waveform.

12
lib/ft8/subtractft8.f90
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@ -11,16 +11,22 @@ subroutine subtractft8(dd,itone,f0,dt)
parameter (NMAX=15*12000,NFRAME=1920*79)
parameter (NFFT=NMAX,NFILT=1400)
real*4 dd(NMAX), window(-NFILT/2:NFILT/2)
real*4 dd(NMAX), window(-NFILT/2:NFILT/2), xjunk
complex cref,camp,cfilt,cw
integer itone(79)
logical first
data first/.true./
common/heap8/cref(NFRAME),camp(NMAX),cfilt(NMAX),cw(NMAX)
common/heap8/cref(NFRAME),camp(NMAX),cfilt(NMAX),cw(NMAX),xjunk(NFRAME)
save first
nstart=dt*12000+1
call genft8refsig(itone,cref,f0)
! call genft8refsig(itone,cref,f0)
nsym=79
nsps=1920
fs=12000.0
icmplx=1
bt=4.0 ! Temporary compromise?
call gen_ft8wave(itone,nsym,nsps,bt,fs,f0,cref,xjunk,icmplx,NFRAME)
camp=0.
do i=1,nframe
id=nstart-1+i

5
widgets/mainwindow.cpp
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@ -102,7 +102,7 @@ extern "C" {
void genft4_(char* msg, int* ichk, char* msgsent, int itone[],
fortran_charlen_t, fortran_charlen_t);
void gen_ft8wave_(int itone[], int* nsym, int* nsps, float* fsample, float* f0,
void gen_ft8wave_(int itone[], int* nsym, int* nsps, float* bt, float* fsample, float* f0,
float xjunk[], float wave[], int* icmplx, int* nwave);
void gen_ft4wave_(int itone[], int* nsym, int* nsps, float* fsample, float* f0,
@ -3701,10 +3701,11 @@ void MainWindow::guiUpdate()
int nsym=79;
int nsps=4*1920;
float fsample=48000.0;
float bt=2.0;
float f0=ui->TxFreqSpinBox->value() - m_XIT;
int icmplx=0;
int nwave=nsym*nsps;
gen_ft8wave_(const_cast<int *>(itone),&nsym,&nsps,&fsample,&f0,foxcom_.wave,
gen_ft8wave_(const_cast<int *>(itone),&nsym,&nsps,&bt,&fsample,&f0,foxcom_.wave,
foxcom_.wave,&icmplx,&nwave);
if(SpecOp::FOX == m_config.special_op_id()) {