Radio Buttons: ungewollte checked Auswahl vermeiden

 
<form  method="post" name="form1" target="_self"><br>  
	
   <input name="radioSO" type="radio" onChange="changedSO(this);" value="GO"><label>zur GO</label><br>  
   <input name="radioSO" type="radio" onChange="changedSO(this);" value="PB"><label>pers. Bemerkung</label><br>  
   <input name="radioSO" type="radio" onChange="changedSO(this);" value="LR"><label>Anwesenheit LR</label><br>  
   <input name="radioSO" type="radio" onChange="changedSO(this);" value="SO"><label>Sonstiges</label><br>  
   <input name="radioSO" type="radio" style="display:none;" value="xx" checked="checked"><label></label><br>  

</form>

function changedSO(rb) {
 $.ajax({ 
url: 'Art2_SO.php', data: {tabelle: Tabelle, aart2: rb.value},   
datatype: 'json', type: 'POST',   
success: function(data) { 
//window.location.reload(); 
} }); 
 
}