<?php if(get_field('repeater_field_name')): ?>
<ul>
<?php while(has_sub_field('repeater_field_name')): ?>
<?php if( get_sub_field('sub_field_1') ): ?>
<li>sub_field_1 = <?php the_sub_field('sub_field_1'); ?></li>
<?php endif; ?>
<?php endwhile; ?>
</ul>
<?php endif; ?>