function nchar(c)

! Convert ascii number, letter, or space to 0-36 for callsign packing.

  character c*1

  n=0                                    !Silence compiler warning
  if(c.ge.'0' .and. c.le.'9') then
     n=ichar(c)-ichar('0')
  else if(c.ge.'A' .and. c.le.'Z') then
     n=ichar(c)-ichar('A') + 10
  else if(c.ge.'a' .and. c.le.'z') then
     n=ichar(c)-ichar('a') + 10
  else if(c.ge.' ') then
     n=36
  else
     Print*,'Invalid character in callsign ',c,' ',ichar(c)
     call exit(1)
  endif
  nchar=n

  return
end function nchar