diff --git a/lib/jt4.f90 b/lib/jt4.f90
index 4d91e1541..214072551 100644
--- a/lib/jt4.f90
+++ b/lib/jt4.f90
@@ -3,7 +3,6 @@ module jt4
   integer iutc(MAXAVE)
   integer nfsave(MAXAVE)
   integer listutc(10)
-  logical ok(MAXAVE)
   real    ppsave(207,7,MAXAVE)           !Accumulated data for message averaging
   real    rsymbol(207,7)                 
   real    dtsave(MAXAVE)
diff --git a/lib/jt4_decode.f90 b/lib/jt4_decode.f90
index 8b55ea6b5..57292d63c 100644
--- a/lib/jt4_decode.f90
+++ b/lib/jt4_decode.f90
@@ -114,6 +114,7 @@ contains
 
     real ccfblue(-5:540)                             !CCF in time
     real ccfred(-224:224)                            !CCF in frequency
+    real ps0(450)
 
 !    real z(458,65)
     logical first,prtavg
@@ -123,7 +124,7 @@ contains
     data first/.true./,nutc0/-999/,nfreq0/-999999/
     save
 
-    if(first .or. nclearave) then
+    if(first) then
        nsave=0
        first=.false.
        blank='                      '
@@ -154,15 +155,15 @@ contains
 
 ! Attempt to synchronize: look for sync pattern, get DF and DT.
     call timer('sync4   ',0)
-    call sync4(dat,npts,ntol,1,nfqso,4,mode4,minw+1,dtx,dfx,    &
-         snrx,snrsync,ccfblue,ccfred,flip,width)
+    mousedf=nint(nfqso + 1.5*4.375*mode4 - 1270.46)
+    call sync4(dat,npts,ntol,1,MouseDF,4,mode4,minw+1,dtx,dfx,    &
+         snrx,snrsync,ccfblue,ccfred,flip,width,ps0)
     sync=snrsync
     dtxz=dtx-0.8
     nfreqz=dfx + 1270.46 - 1.5*4.375*mode4
     call timer('sync4   ',1)
 
     snrx=db(sync) - 26.
-    if(snrx.lt.-26.0) snrx=-26.0
     nsnr=nint(snrx)
     if(sync.lt.syncmin) then
        if (associated (this%decode_callback)) then
@@ -226,8 +227,8 @@ contains
              nsave=mod(nsave-1,64)+1
              call timer('avg4    ',0)
              call this%avg4(nutc,sync,dtx,flip,nfreq,mode4,ntol,ndepth,neme,  &
-                  nclearave,mycall,hiscall,hisgrid,nfanoave,avemsg,qave,      &
-                  deepave,ich,ndeepave)
+                  mycall,hiscall,hisgrid,nfanoave,avemsg,qave,deepave,ich,    &
+                  ndeepave)
              call timer('avg4    ',1)
           endif
 
@@ -284,8 +285,7 @@ contains
   end subroutine wsjt4
 
   subroutine avg4(this,nutc,snrsync,dtxx,flip,nfreq,mode4,ntol,ndepth,neme,   &
-       nclearave, mycall,hiscall,hisgrid,nfanoave,avemsg,qave,deepave,        &
-       ichbest,ndeepave)
+       mycall,hiscall,hisgrid,nfanoave,avemsg,qave,deepave,ichbest,ndeepave)
 
 ! Decodes averaged JT4 data
 
@@ -297,14 +297,14 @@ contains
     character*1 csync,cused(64)
     real sym(207,7)
     integer iused(64)
-    logical first,nclearave
+    logical first
     data first/.true./
     save
 
-    if(first .or. nclearave) then
+    if(first) then
        iutc=-1
        nfsave=0
-       dtdiff=0.25
+       dtdiff=0.2
        first=.false.
     endif
 
@@ -320,33 +320,19 @@ contains
     flipsave(nsave)=flip
     ppsave(1:207,1:7,nsave)=rsymbol(1:207,1:7)  
 
-10  dtsum=0.
-    nsum=0
-    ok=.false.
-
-    do i=1,nsave
-       if(iutc(i).lt.0) cycle
-       if(mod(iutc(i),2).ne.mod(nutc,2)) cycle    !Use only same sequence
-       if(abs(nfreq-nfsave(i)).gt.ntol) cycle     !Freq must match
-       if(flip.ne.flipsave(i)) cycle              !Sync (*/#) must match
-       if(abs(dtxx-dtsave(i)).gt.2*dtdiff) cycle  !Pk-to-pk DT range < 2*dtdiff
-       dtsum=dtsum+dtsave(i)
-       nsum=nsum+1
-       ok(i)=.true.
-    enddo
-    dtave=0.
-    if(nsum.ge.1) dtave=dtsum/nsum
-
-    sym=0.
+10  sym=0.
     syncsum=0.
     dtsum=0.
     nfsum=0
     nsum=0
-    do i=1,nsave
+
+    do i=1,64
        cused(i)='.'
-       dttest=dtsave(i)-dtave
-       if(.not.ok(i)) cycle
-       if(abs(dttest).gt.dtdiff) cycle          !DT must match
+       if(iutc(i).lt.0) cycle
+       if(mod(iutc(i),2).ne.mod(nutc,2)) cycle  !Use only same sequence
+       if(abs(dtxx-dtsave(i)).gt.dtdiff) cycle  !DT must match
+       if(abs(nfreq-nfsave(i)).gt.ntol) cycle   !Freq must match
+       if(flip.ne.flipsave(i)) cycle            !Sync (*/#) must match
        sym(1:207,1:7)=sym(1:207,1:7) +  ppsave(1:207,1:7,i)
        syncsum=syncsum + syncsave(i)
        dtsum=dtsum + dtsave(i)
diff --git a/lib/sync4.f90 b/lib/sync4.f90
index 4fdf6f481..c7f33b470 100644
--- a/lib/sync4.f90
+++ b/lib/sync4.f90
@@ -1,5 +1,5 @@
-subroutine sync4(dat,jz,ntol,NFreeze,nfqso,mode,mode4,minwidth,    &
-     dtx,dfx,snrx,snrsync,ccfblue,ccfred1,flip,width)
+subroutine sync4(dat,jz,ntol,NFreeze,MouseDF,mode,mode4,minwidth,    &
+     dtx,dfx,snrx,snrsync,ccfblue,ccfred1,flip,width,ps0)
 
 ! Synchronizes JT4 data, finding the best-fit DT and DF.  
 
@@ -9,6 +9,7 @@ subroutine sync4(dat,jz,ntol,NFreeze,nfqso,mode,mode4,minwidth,    &
   integer ntol                     !Range of DF search
   real dat(jz)
   real psavg(NHMAX)                !Average spectrum of whole record
+  real ps0(450)                    !Avg spectrum for plotting
   real s2(NHMAX,NSMAX)             !2d spectrum, stepped by half-symbols
   real ccfblue(-5:540)             !CCF with pseudorandom sequence
   real ccfred(-450:450)            !Peak of ccfblue, as function of freq
@@ -22,6 +23,9 @@ subroutine sync4(dat,jz,ntol,NFreeze,nfqso,mode,mode4,minwidth,    &
   data nch/1,2,4,9,18,36,72/
   save
 
+!  write(*,3001) 'A',ntol,nfreeze,mousedf,mode,mode4,minwidth
+!3001 format(a1,6i6)
+
 ! Do FFTs of twice symbol length, stepped by half symbols.  Note that 
 ! we have already downsampled the data by factor of 2.
   nsym=207
@@ -42,21 +46,18 @@ subroutine sync4(dat,jz,ntol,NFreeze,nfqso,mode,mode4,minwidth,    &
   nsmo=min(10*mode4,150)
   call flat1b(psavg,nsmo,s2,nh,nsteps,NHMAX,NSMAX)        !Flatten spectra
 
-  if(mode4.ge.9) then
-     call smo(psavg,nh,tmp,mode4/4)
-     psavg=psavg/(mode4/4.0)
-     do j=1,nsteps
-        call smo(s2(1,j),nh,tmp,mode4/4)
-     enddo
-     s2=s2/(mode4/4.0)
-  endif
+  if(mode4.ge.9) call smo(psavg,nh,tmp,mode4/4)
+
+  i0=132
+  do i=1,450
+     ps0(i)=5.0*(psavg(i0+2*i) + psavg(i0+2*i+1) - 2.0)
+  enddo
 
 ! Set freq and lag ranges
   famin=200.0 + 3*mode4*df
   fbmax=2700.0 - 3*mode4*df
   fa=famin
   fb=fbmax
-  mousedf=nint(nfqso + 1.5*4.375*mode4 - 1270.46)
   if(NFreeze.eq.1) then
      fa=max(famin,1270.46+MouseDF-ntol)
      fb=min(fbmax,1270.46+MouseDF+ntol)
@@ -76,23 +77,21 @@ subroutine sync4(dat,jz,ntol,NFreeze,nfqso,mode,mode4,minwidth,    &
   ccfred=0.
   jmax=-1000
   jmin=1000
-!  rewind 83
 
   do ich=minwidth,7                       !Find best width
+     kz=nch(ich)/2
      savered=.false.
-     do i=ia,ib                           !Find best frequency channel for CCF
+     do i=ia+kz,ib-kz                     !Find best frequency channel for CCF
         call xcor4(s2,i,nsteps,nsym,lag1,lag2,ich,mode4,ccfblue,ccf0,   &
              lagpk0,flip)
         j=i-i0 + 3*mode4
         if(j.ge.-372 .and. j.le.372) then
            ccfred(j)=ccf0
-!           write(83,4001) i*df,ccf0
-!4001       format(f10.1,e12.3)
            jmax=max(j,jmax)
            jmin=min(j,jmin)
         endif
 
-! Normalize ccfblue so that baseline rms = 1.0
+! Find rms of the CCF, without main peak
         call slope(ccfblue(lag1),lag2-lag1+1,lagpk0-lag1+1.0)
         sync=abs(ccfblue(lagpk0))
 
@@ -174,28 +173,7 @@ subroutine sync4(dat,jz,ntol,NFreeze,nfqso,mode,mode4,minwidth,    &
   enddo
   width=(i-i1)*df
 
-!  rewind 80
-!  rewind 81
-!  rewind 82
-
-!  do i=1,NHMAX
-!     write(80,3004) i*df,psavg(i),sum(s2(i,1:nsteps))
-!3004 format(f10.1,2e12.3)
-!  enddo
-
-!  do i=jmin,jmax
-!     write(81,3001) i,ccfred1(i),width
-!3001 format(i5,2f10.3)
-!  enddo
-!  do i=lag1,lag2
-!     write(82,3002) i,ccfblue(i)
-!3002 format(i5,f10.3)
-!  enddo
-!  flush(80)
-!  flush(81)
-!  flush(82)
-!  flush(83)
-
   return
 end subroutine sync4
 
+include 'flat1b.f90'