JS on checkbox Change enable or disable a radio button

I have a check box that I want to enable these radio buttons. what I have does not work. how can I JS that?

im new. :(

var sipch = document.querySelector("input[name=sip]");
sipch.addEventListener( 'change', function() {
    if(sipch.checked) {
        document.getElementById("protocol").disabled=false;
    } else {
        document.getElementById("protocol").disabled=true;
    }
});

<input type="checkbox" name="sip" onsubmit="goPFive(event)" method="get">do this?
<input type="radio" class="testD" name="protocol" value="udp" disabled checked/>UDP
<input type="radio" class="testD" name="protocol" value="tcp" disabled />TCP