It does not matter for how many hours you talk over the phone or have a video chat, but it is important to talk every day. Share your day's experience with your husband and ask him about his routine as well. Express your feelings, since this is your only way of sharing some intimacy with your better half. If you have kids, make sure he talks to them before they go to bed. This will help in strengthening their bond as well. If you are unable to call him, then make sure that you leave him a small text message, so that you two stay in touch somehow.