def read_radolan_header(fid):
    """Reads radolan ASCII header and returns it as string

    Parameters
    ----------
    fid : object
        file handle

    Returns
    -------
    header : string
    """
    # rewind, just in case...
    fid.seek(0, 0)

    header = ''
    while True:
        mychar = fid.read(1)
        if not mychar:
            raise EOFError('Unexpected EOF detected while reading '
                           'RADOLAN header')
        if mychar == b'\x03':
            break
        header += str(mychar.decode())
    return header