How to tell SED to emit output in 8-bit ASCII only?

I have to mangle some "plain ASCII" text file (i.e. 8 bits/characters where the text DOES contain characters like Umlauts and accented characters from the upper 7-bits range, i.e. with hex codes in [128..254]).

For this I am trying to use SED which I downloaded as part of cygwin package (yes, I am doing this one Windoze...).

Alas, SED emits the result using Unicode-16 characters (i.e. 16 bits/characters), which the program for which the output is intended can't handle. Can one tell SED to NOT emit Unicode-16 characters but force it to emit 8-bit characters (Unicode-8) only?