Adding category to subdomain

Hi, I have wordpress already up and running on my domain, and was wondering if the following would be possible:

I would like to create a new subdomain, and assign a category to it. This category would only show under that subdomain, so updates to my new category would not affect my rss feeds for the main blog.

The reason why I would like to do that, is because I’ll be talking about two completely different topics, and the main blog already gets syndicated by major services in the topic, and adding something that has absolutely nothing to do with it would make its reputation go down.

The only quick solution I could think of, is re-installing wordpress o the subdomain, but that will mean having to maintain two installations, and ideally, I would like to stick to the same install, but posting to two different sources by defining the category.

Is that even possible?

Thanks in advance