Because ng-repeat creates its own scope and what you are trying to do is assign the value to the parent scope from the child scope. So you can do
<input type="radio" ng-model="$parent.contactname" name="group1" value="{{contact.name}}">
Because ng-repeat creates its own scope and what you are trying to do is assign the value to the parent scope from the child scope. So you can do
<input type="radio" ng-model="$parent.contactname" name="group1" value="{{contact.name}}">