$ trans :de -brief "over" >2.ascii.de.txt
$ trans :de -brief "He must." >>2.ascii.de.txt
$ cat 2.ascii.de.txt 
Über
Er muss.
$ iconv -f us-ascii -t UTF-8 2.ascii.de.txt -o 2.de.utf8.txt
iconv: illegal input sequence at position 0
$