Ionic - Check 2 radio buttons (different lists) by default

I am currently taking my first steps in Ionic, and trying to create an app.

In this example, I have 2 radio button lists (with options 1, 2, 3 and options 4, 5, 6):

I would like both radio buttons 2 and 4 to be checked by default.

Why is only radio button 4 checked?

What am I missing?

Code below.

From the model HTML:

<ion-view view-title="Radio button demo">
  <ion-header-bar align-title="left" class="bar-positive">
    <h1 class="title">Chosen option: {{item}}, {{item2}}</h1>
   </ion-header-bar>  
 <ion-content>
<ion-list>
  <ion-radio ng-repeat="i in items" ng-value="i.Id" ng-model="item.itemval" >{{i.Name}}</ion-radio>
</ion-list>
<ion-list>
  <ion-radio ng-repeat="i in items2" ng-value="i.Id" ng-model="item2.itemval" >{{i.Name}}</ion-radio>
</ion-list>
  </ion-content>
</ion-view>

From the controller javascript file:

.controller("MainCtrl", function($scope) {
  $scope.items = [
    { Id: 1, Name: "Test 1", value: "t1" },
    { Id: 2, Name: "Test 2", value: "t2" },
    { Id: 3, Name: "Test 3", value: "t3" }
  ];

  $scope.items2 = [
    { Id: 4, Name: "Test 4", value: "t4" },
    { Id: 5, Name: "Test 5", value: "t5" },
    { Id: 6, Name: "Test 6", value: "t6" }
  ];

  $scope.item = { itemval: "2" };
  $scope.item2 = { itemval: "4" };
});