Increase archive length for category

add_action( 'pre_get_posts', 'zed1_increase_archive_length' );
function zed1_increase_archive_length( $query ) {

    // if this is not the main query on the page, do nothing
    if ( !$query->is_main_query() )
        return;

    // if this is our category increase number of posts
    if ( $query->is_category( 'podcast' ) ) {
        $query->set( 'posts_per_page', 999 );
    }
} // end zed1_increase_archive_length