My site feed is Atom, I need RSS

This is for my site at http://www.digitl.co.nz/

According to the WordPress Codex, the following URLs should get feeds from my site in different feed formats:

http://example.com/feed/
http://example.com/feed/rss/
http://example.com/feed/rss2/
http://example.com/feed/rdf/
http://example.com/feed/atom/

In practice mine are all identical and all point back to /feed/

I think the default at /feed/ is an atom feed.

I need to produce an RSS or RSS2 feed. How do I do this?