diff --git a/lib/77bit/packjt77.f90 b/lib/77bit/packjt77.f90
index 47cd3b6bb..e72b5add6 100644
--- a/lib/77bit/packjt77.f90
+++ b/lib/77bit/packjt77.f90
@@ -15,6 +15,38 @@ module packjt77
 
   contains
 
+subroutine readhash(filename)
+   character(len=*), intent(in) :: filename
+   logical :: file_exists
+                                                                                                                                  
+   inquire(file=filename, exist=file_exists)
+   if (file_exists) then
+      open(unit=10, file=filename, access='STREAM', form='UNFORMATTED', STATUS='OLD')
+                                                                                                                                  
+      READ(10) calls10
+      READ(10) calls12
+      READ(10) calls22
+      READ(10) ihash22
+      READ(10) nzhash
+      close(unit=10)
+   endif
+                                                                                                                                  
+end subroutine readhash
+                                                                                                                                  
+subroutine writehash(filename)
+   character(len=*), intent(in) :: filename
+                                                                                                                                  
+   open(unit=10, file=filename, access='STREAM', form='UNFORMATTED', STATUS='REPLACE')
+                                                                                                                                  
+   WRITE(10) calls10
+   WRITE(10) calls12
+   WRITE(10) calls22
+   WRITE(10) ihash22
+   WRITE(10) nzhash
+   close(unit=10)
+                                                                                                                                  
+end subroutine writehash
+
 subroutine hash10(n10,c13)
 
   character*13 c13
diff --git a/lib/jt9.f90 b/lib/jt9.f90
index d284f6dd2..2ab955ffb 100644
--- a/lib/jt9.f90
+++ b/lib/jt9.f90
@@ -10,7 +10,8 @@ program jt9
   use timer_module, only: timer
   use timer_impl, only: init_timer, fini_timer
   use readwav
-
+  use packjt77
+  
   include 'jt9com.f90'
 
   integer*2 id2a(180000)
@@ -26,8 +27,8 @@ program jt9
        fhigh=4000,nrxfreq=1500,ndepth=1,nexp_decode=0,nQSOProg=0
   logical :: read_files = .true., tx9 = .false., display_help = .false.,     &
        bLowSidelobes = .false., nexp_decode_set = .false.,                   &
-       have_ntol = .false.
-  type (option) :: long_options(33) = [                                      &
+       have_ntol = .false., persist_hash = .false.
+  type (option) :: long_options(34) = [                                      &
     option ('help', .false., 'h', 'Display this help message', ''),          &
     option ('shmem',.true.,'s','Use shared memory for sample data','KEY'),   &
     option ('tr-period', .true., 'p', 'Tx/Rx period, default SECONDS=60',    &
@@ -75,6 +76,8 @@ program jt9
     option ('my-grid', .true., 'G', 'my grid locator', 'GRID'),              &
     option ('his-call', .true., 'x', 'his callsign', 'CALL'),                &
     option ('his-grid', .true., 'g', 'his grid locator', 'GRID'),            &
+    option ('persist-hash', .true.,                                          &
+       'P', 'persist hashcodes', 'PATH'),                                    &
     option ('experience-decode', .true., 'X',                                &
         'experience based decoding flags (1..n), default FLAGS=0',           &
         'FLAGS') ]
@@ -92,7 +95,7 @@ program jt9
   TRperiod=60.d0
 
   do
-     call getopt('hs:e:a:b:r:m:p:d:f:F:w:t:9876543WYqkTL:S:H:c:G:x:g:X:Q:',     &
+     call getopt('hs:e:a:b:r:m:p:d:f:F:w:t:9876543WYqkTL:S:H:c:G:x:g:P:X:Q:',   &
           long_options,c,optarg,arglen,stat,offset,remain,.true.)
      if (stat .ne. 0) then
         exit
@@ -164,6 +167,9 @@ program jt9
            read (optarg(:arglen), *) hiscall
         case ('g')
            read (optarg(:arglen), *) hisgrid
+        case ('P')
+           hash_file = optarg(:arglen)
+           persist_hash = .true.
         case ('X')
            read (optarg(:arglen), *) nexp_decode
            nexp_decode_set = .true.
@@ -188,6 +194,10 @@ program jt9
      go to 999
   endif
 
+  if (persist_hash) then
+     call readhash(hash_file)
+  end if
+
   iret=fftwf_init_threads()            !Initialize FFTW threading 
 
 ! Default to 1 thread, but use nthreads for the big ones
@@ -378,4 +388,8 @@ program jt9
   call filbig(a,-1,1,0.0,0,0,0,0,0)        !used for FFT plans
   call fftwf_cleanup_threads()
   call fftwf_cleanup()
+
+  if (persist_hash) then
+     call writehash(hash_file)
+  end if
 end program jt9
diff --git a/lib/prog_args.f90 b/lib/prog_args.f90
index 63cdb7928..ff2a116d7 100644
--- a/lib/prog_args.f90
+++ b/lib/prog_args.f90
@@ -1,4 +1,5 @@
 MODULE prog_args
   CHARACTER(len=80) :: shm_key
   CHARACTER(len=500) :: exe_dir = '.', data_dir = '.', temp_dir = '.'
+  CHARACTER(len=500) :: hash_file = 'hash.dat'
 END MODULE prog_args