Jo, ten script
<script>
$(document).ready(function(){
$("#id_form").on("submit", function(){
$('input:radio:not(:checked)').each(function() {
$('#not_selected_stations').val($('#not_selected_stations').val()+";"+$( this ).val());
});
})
});
</script>
se mi líbí, že to udělá ono '#not_selected_stations'