Use a ListBox instead. Check the sample here. For example, define ListBox in a xaml
<ListBox x:Name="MyList">
and then in codebehind
var MyListData = new List<ChannelNewsLstControl>();
MyListData.Add(new ChannelNewsLstControl {name = "MyFirstChannelName});
MyList.ItemsSource=MyListData;
If you have really lots of items, i'd recommend to use Telerik's DataBoundListBox as it is much faster than a normal ListBox (at least, for wp7) and supports virtualization and async loading. Sample would be pretty the same, as component is inherited ListBox and adding own features mentioned before.
EDIT: final answer:
Try to put a grid inside of your ItemTemplate and set its RowDefinition.Height = "Auto".
See some details here