Upload flat file with no field separators

Hi,

how can i upload a flat file containing no field separators? That means the only way to identify rows is to count the characters. If i look at the documention two parameters should help:

- fieldFixedLengths

- fieldSeparator

Problem: If i add the fieldFixedLengths parameter the system expects a comma as field separator (online docu). Why?? Of course i can choose another field separator - but any field separator must be at least as long as one character (online docu).

Any ideas?