Tweak decoder for better decodes under poor conditions

lib/ft8/DXpedQuickStart.txt

@@ -1,126 +0,0 @@
-		Quick Start for DXpedition Mode
-		-------------------------------
-
-These notes are intended for operators already familiar with WSJT-X
-and FT8 mode.  QSOs between the Dxpedition ("Fox") and other stations
-("Hounds") are completed with as little as one transmission per Hound,
-as in the following examples:
-
-----------------------------------------------------------------------------
-    Fox (300-600 Hz)                 Hounds
-----------------------------------------------------------------------------
-1.  CQ KH1DX AJ10
-2.                                   KH1DX K1ABC FN42, KH1DX W9XYZ EN37, ...
-3.  K1ABC KH1DX -13
-4.                                   KH1DX K1ABC R-11
-5.  K1ABC RR73; W9XYZ <KH1DX> -17
-6.                                   KH1DX W9XYZ R-16
-7.  W9XYZ RR73; G4AAA <KH1DX> -09
-8.  ...
-----------------------------------------------------------------------------
-
-Everybody sets dial frequency to an agreed number and uses CAT control
-with Split Operation (either *Rig* or *Fake It*).  Fox transmits up to
-5 signals simultaneously, at audio frequencies 300, 360, ... 540
-Hz.  Hounds make initial calls (e.g., line 2 above) anywhere in the
-range 1000 - 4000 Hz.  They send "R+rpt" 350 Hz above the frequency
-where Fox called them.
-
-
-INSTRUCTIONS FOR FOX
---------------------
-
-1. Start WSJT-X in FT8 mode.  Select *Fox* on the *Settings ->
-Advanced tab*.  On the main window, check *Tx even/1st*, *Auto Seq*,
-and *Hold Tx Freq*; uncheck *Call 1st*.  Set *Tx 300 Hz* and select
-Tab 3.
-
-2. In Fox mode the left window (called "Band Activity" in normal FT8
-mode) is labeled "Stations calling DXpedition <MyCall>".  It will be
-filled with a sorted list of calling Hounds.  You can sort by Call,
-Grid, S/N, Distance, or Random order by using the comboBox at top
-right of Tab 3.  You can limit the displayed Hound callsigns to those
-no stronger than *Max dB*.  Fox might use this feature to discourage
-Hounds from engaging in a QRO arms race.
-
-3. *N Slots* sets the number of simultaneous Fox signals to be used.
-Fox carries out as many as *N Slots* QSOs simultaneously.
-
-4. *Repeats* sets the maximum number of repeat transmissions of the
-same message.  A QSO is aborted when this number would be exceeded.
-
-5. The *CQ* comboBox on Tab 3 offers a selection of directed CQ
-messages.  *Reset* clears the QSO queue.
-
-6. The Fox operator's main task is to select Hounds to be called and
-worked.  The text box on Tab 3 holds the "QSO queue": a list of Hound
-calls to be worked.  Hit Enter to select the top callsign from the
-sorted list of callers (left window), or double-click on any
-particular call.  Either actiion moves that Hound into the "QSO
-queue".
-
-7. The right window displays decodes of signals below 1000 Hz.
-Normally these should include only Hound messages containing "R+rpt"
-and Fox's own transmissions.
-
-8. To get things started, toggle *Enable Tx* to red.  If a Hound call
-is available in the QSO queue, that station will be called.  If the
-QSO queue is empty, Fox calls CQ.
-
-9. If you're using Nslots = 2 or higher, your signal no longer has
-a constant envelope.  To avoid producing intermod sidebands you need
-to ensure linearity in your Tx system.  One way to get things about right
-is to use the WSJT-X *Tune* button to generate a pure tone.  Reduce the
-Tx audio level until your power output decreases by 10% or so.  Use this
-level for your Fox transmissions.
-
-NOTE: If you are generating Nslots signals, the average power in each one
-will be 1/Nslots^2 of its normal value for single-signal transmissions.
-
-Nslots  Relative dB
--------------------
-  1        0
-  2       -6
-  3      -9.5
-  4      -12
-  5      -14
-
-
-The following features are not yet implemented for Fox:
-
-1. Enforce all required settings
-2. Tx message timeout
-3. Manual abort of selected QSO
-4. All Tx and Rx messages to all.txt
-5. Additional sort criteria for Hound calls
-6. Selectable timeout for keeping Hounds in the sorted list
-7. Display number of active callers
-8. Display QSO rate
-
-
-INSTRUCTIONS FOR HOUND
-----------------------
-
-1. Start WSJT-X in FT8 mode.  Select *Hound* On the *Settings ->
-Advanced* tab.  On the main window check *Auto Seq* and uncheck *Tx
-even/1st*, *Call 1st*, and *Hold Tx Freq*.  Set *Tx nnnn Hz* to some
-frequency between 1000 and 4000 Hz, and select *Tab 1*.  Enter Fox's
-callsign and locator in DX Call and DX Grid, select Tx1, and start
-*Monitor*.
-
-2. When you have copied Fox, hit *Enable Tx* to call him.  You may
-keep calling until he answers.  You may wish to move your TxFreq
-around, hoping to find a clear calling frequency.
-
-3. When you are called by Fox with a signal report, your next
-transmission will automatically be sent as Tx3 ("R+rpt").  When Fox
-receives that message he responds with "RR73", and your QSO is
-complete!
-
-
-The following features are not yet implemented for Hound:
-
-1. Force all required settings
-2. React properly to directed CQs from Fox
-3. Disable Tx2, 4, 5, 6
-4. For Tx1, enforce TxFreq >= 1000 Hz

lib/ft8/ft8_downsample.f90

@@ -5,15 +5,23 @@ subroutine ft8_downsample(dd,newdat,f0,c1)
   parameter (NMAX=15*12000,NSPS=1920)
   parameter (NFFT1=192000,NFFT2=3200)      !192000/60 = 3200
   
-  logical newdat
+  logical newdat,first
   complex c1(0:NFFT2-1)
   complex cx(0:NFFT1/2)
-  real dd(NMAX),x(NFFT1)
+  real dd(NMAX),x(NFFT1),taper(0:100)
   equivalence (x,cx)
-  save cx
+  data first/.true./
+  save cx,first,taper
 
+  if(first) then
+     pi=4.0*atan(1.0)
+     do i=0,100
+       taper(i)=0.5*(1.0+cos(i*pi/100))
+     enddo
+     first=.false.
+  endif
   if(newdat) then
-! Data in dd have changed, recompute the long FFT     
+! Data in dd have changed, recompute the long FFT
      x(1:NMAX)=dd
      x(NMAX+1:NFFT1)=0.                       !Zero-pad the x array
      call four2a(cx,NFFT1,1,-1,0)             !r2c FFT to freq domain
@@ -23,9 +31,9 @@ subroutine ft8_downsample(dd,newdat,f0,c1)
   df=12000.0/NFFT1
   baud=12000.0/NSPS
   i0=nint(f0/df)
-  ft=f0+8.0*baud
+  ft=f0+8.5*baud
   it=min(nint(ft/df),NFFT1/2)
-  fb=f0-1.0*baud
+  fb=f0-1.5*baud
   ib=max(1,nint(fb/df))
   k=0
   c1=0.
@@ -33,6 +41,8 @@ subroutine ft8_downsample(dd,newdat,f0,c1)
    c1(k)=cx(i)
    k=k+1
   enddo
+  c1(0:100)=c1(0:100)*taper(100:0:-1)
+  c1(k-1-100:k-1)=c1(k-1-100:k-1)*taper
   c1=cshift(c1,i0-ib)
   call four2a(c1,NFFT2,1,1,1)            !c2c FFT back to time domain
   fac=1.0/sqrt(float(NFFT1)*NFFT2)

lib/ft8/ft8b.f90

@@ -28,7 +28,7 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,lapon,lapcqonly,   &
   integer nappasses(0:5)  !Number of decoding passes to use for each QSO state
   integer naptypes(0:5,4) ! (nQSOProgress, decoding pass)  maximum of 4 passes for now
   integer*1, target:: i1hiscall(12)
-  complex cd0(3200)
+  complex cd0(0:3199)
   complex ctwk(32)
   complex csymb(32)
   logical first,newdat,lsubtract,lapon,lapcqonly,nagain
@@ -126,7 +126,8 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,lapon,lapcqonly,   &
   do k=1,NN
     i1=ibest+(k-1)*32
     csymb=cmplx(0.0,0.0)
-    if( i1.ge.1 .and. i1+31 .le. NP2 ) csymb=cd0(i1:i1+31)
+    !if( i1.ge.1 .and. i1+31 .le. NP2 ) csymb=cd0(i1:i1+31)
+    if( i1.ge.0 .and. i1+31 .le. NP2-1 ) csymb=cd0(i1:i1+31)
     call four2a(csymb,32,1,-1,1)
     s2(0:7,k)=abs(csymb(1:8))/1e3
   enddo  
@@ -181,7 +182,7 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,lapon,lapcqonly,   &
      bmetap(i2)=r2
      bmetap(i1)=r1
 ! Max log metric
-     psl=log(ps)
+     psl=log(ps+1e-32)
      r1=max(psl(1),psl(3),psl(5),psl(7))-max(psl(0),psl(2),psl(4),psl(6))
      r2=max(psl(2),psl(3),psl(6),psl(7))-max(psl(0),psl(1),psl(4),psl(5))
      r4=max(psl(4),psl(5),psl(6),psl(7))-max(psl(0),psl(1),psl(2),psl(3))

lib/ft8/sync8.f90

@@ -37,11 +37,6 @@ subroutine sync8(dd,nfa,nfb,syncmin,nfqso,s,candidate,ncand,sbase)
      savg=savg + s(1:NH1,j)                   !Average spectrum
   enddo
   call baseline(savg,nfa,nfb,sbase)
-!  savg=savg/NHSYM
-!  do i=1,NH1
-!     write(51,3051) i*df,savg(i),db(savg(i))
-!3051 format(f10.3,e12.3,f12.3)
-!  enddo
 
   ia=max(1,nint(nfa/df))
   ib=nint(nfb/df)
@@ -49,6 +44,9 @@ subroutine sync8(dd,nfa,nfb,syncmin,nfqso,s,candidate,ncand,sbase)
   nfos=NFFT1/NSPS   ! # frequency bin oversampling factor
   jstrt=0.5/tstep
 
+  candidate0=0.
+  k=0
+
   do i=ia,ib
      do j=-JZ,+JZ
         ta=0.
@@ -95,20 +93,18 @@ subroutine sync8(dd,nfa,nfb,syncmin,nfqso,s,candidate,ncand,sbase)
   iz=ib-ia+1
   call indexx(red(ia:ib),iz,indx)
   ibase=indx(nint(0.40*iz)) - 1 + ia
+  if(ibase.lt.1) ibase=1
+  if(ibase.gt.nh1) ibase=nh1
   base=red(ibase)
   red=red/base
 
-  candidate0=0.
+  do i=1,min(200,iz)
-  k=0
+    n=ia + indx(iz+1-i) - 1
-  do i=1,200
+    if(red(n).lt.syncmin.or.isnan(red(n)).or.k.eq.200) exit
-     ji=iz+1-1
+    k=k+1
-     if(ji.eq.0) exit
+    candidate0(1,k)=n*df
-     n=ia + indx(ji) - 1
+    candidate0(2,k)=(jpeak(n)-1)*tstep
-     if(red(n).lt.syncmin) exit
+    candidate0(3,k)=red(n)
-     if(k.lt.200) k=k+1
-     candidate0(1,k)=n*df
-     candidate0(2,k)=(jpeak(n)-1)*tstep
-     candidate0(3,k)=red(n)
   enddo
   ncand=k
 
@@ -123,9 +119,6 @@ subroutine sync8(dd,nfa,nfb,syncmin,nfqso,s,candidate,ncand,sbase)
               if(candidate0(3,i).lt.candidate0(3,j)) candidate0(3,i)=0.
            endif
         enddo
-!        write(*,3001) i,candidate0(1,i-1),candidate0(1,i),candidate0(3,i-1),  &
-!             candidate0(3,i)
-!3001    format(i2,4f8.1)
      endif
   enddo