Modified the FT8 crc12 using XOR 42 so we do not interfere with standard FT8 stations

lib/ft8/chkcrc12a.f90

@@ -16,6 +16,7 @@ subroutine chkcrc12a(decoded,nbadcrc)
   i1Dec8BitBytes(10)=iand(i1Dec8BitBytes(10),128+64+32)
   i1Dec8BitBytes(11)=0
   icrc12=crc12(c_loc(i1Dec8BitBytes),11)          !CRC12 computed from 75 msg bits
+  icrc12=xor(icrc12, 42)
 
   nbadcrc=1
   if(ncrc12.eq.icrc12) nbadcrc=0

lib/ft8/extractmessage174.f90

@@ -20,6 +20,7 @@ subroutine extractmessage174(decoded,msgreceived,ncrcflag)
   i1Dec8BitBytes(10)=iand(i1Dec8BitBytes(10),128+64+32)
   i1Dec8BitBytes(11)=0
   icrc12=crc12(c_loc(i1Dec8BitBytes),11)          !CRC12 computed from 75 msg bits
+  icrc12=xor(icrc12, 42)
 
   if(ncrc12.eq.icrc12 .or. sum(decoded(57:87)).eq.0) then  !### Kludge ###
 ! CRC12 checks out --- unpack 72-bit message

lib/ft8/foxgen.f90

@@ -73,6 +73,7 @@ subroutine foxgen()
         read(cb88,1003) i1Msg8BitBytes(1:11)
 1003    format(11b8)
         icrc12=crc12(c_loc(i1Msg8BitBytes),11)
+        icrc12=xor(icrc12, 42)
 
         write(cbits,1001) msgbits(1:56),icrc10,nrpt,i3b,icrc12
         read(cbits,1002) msgbits

lib/ft8/genft8.f90

@@ -26,6 +26,7 @@ subroutine genft8(msg,mygrid,bcontest,i3bit,msgsent,msgbits,itone)
   i1Msg8BitBytes(10)=iand(i1Msg8BitBytes(10),128+64+32)
   i1Msg8BitBytes(11)=0
   icrc12=crc12(c_loc(i1Msg8BitBytes),11)
+  icrc12=xor(icrc12, 42)
 
 ! For reference, here's how to check the CRC
 !  i1Msg8BitBytes(10)=icrc12/256

lib/ft8/ldpcsim174.f90

@@ -91,6 +91,7 @@ allocate ( rxdata(N), llr(N) )
 
   i1Msg8BitBytes(10:11)=0
   checksum = crc12 (c_loc (i1Msg8BitBytes), 11)
+  checksum = xor(checksum, 42)
 ! For reference, the next 3 lines show how to check the CRC
   i1Msg8BitBytes(10)=checksum/256
   i1Msg8BitBytes(11)=iand (checksum,255)