WP admin bar + sticky header js

jquery.js

var $document = $(document),
    $header = $('.admin-bar .site-header');


if($(window).width() < 601) {
  $document.scroll(function() {
    if ($document.scrollTop() >= 46) {
      // user scrolled 46 pixels or more;
      $header.css({"top": "0"})
    } else {
      $header.css({"top": "46px"})
    }
    });
} else {
  //nothing
}