[Foreigner]

Такой вариант

Код:

$file = gc file.txt

$enc = [system.text.encoding]

function psiconv ( $f, $t, $string ) {

    $cp1          = $enc::getencoding( $f )
    $cp2          = $enc::getencoding( $t )
    $inputbytes   = $enc::convert( $cp1, $cp2, $cp2.getbytes( $string ))
    $outputstring = $cp2.getstring( $inputbytes )
    
    $outputstring | add-content file1.txt   

}

foreach ($string in $file) {

    psiconv -f "windows-1251" -t "utf-8" $string

}

Где file.txt в 1251, file1.txt в utf-8