     
   // as in datasheet page 12 - modified to include calibration offset
   ULONG data = (frequency * 4294967296) / (180000000 - VfoClockOffset);
+  //                        ^^^^^^^^^^ == 2**32
 
 #if (DEBUG & DEBUG_DDS)
   Serial.printf("dds_update: ONLINE: frequency=%ld, VfoClockOffset=%d, data=%ld\n",

}

//----------------------------------------
// Function to convert an unsigned long into an array of byte digit values.
//     buf      address of buffer for byte results
//     bufsize  size of the 'buf' buffer
//     value    the Frequency value to convert

// The resultant buffer does NOT have a terminating '\0'!
//----------------------------------------

void ulong2buff(char *buf, int bufsize, long value)
{
  char *ptr = buf + bufsize - 1;    // rightmost char in 'buf'

