Hi bobcat - have you checked
http://www.antennaweb.org to see what it says about what you can get and what type of antenna it would take? I believe I've read that unless you have some hills in the way toward Walnut Grove where the Sacto broadcast towers are, you should be good on getting the Sacto locals. With the right antenna and a rotator, you should be able to get both Sacto and San Francisco stations.
What DMA is in your Voom box - Sacto or San Francisco? You can tell which one if you are getting guide data for the stations. I live up in the foothills (Auburn) and my local DMA is Sacto, but I can occasionally get stations from the Bay Area, but with no guide info. BTW - the new "Super DMA" update should solve this problem.
Anyway, check out antennaweb.org if you haven't already to see what it says for an antenna. I'd guess that if you are in the 50 - 70 mile range, it will suggest a large directional and perhaps a pre-amp, and if you want to get both Sacto and Bay Area, a rotator. If you proceed, you'll need to make the call on a UHF only, or a UHF/VHF antenna.
Another good reference for antenna topics is over at the HomeTheaterSpot. Friendly, helpful place. The url to get directly to the antenna forum (they have scores of different forums) is
http://www.hometheaterspot.com/htsthreads/postlist.php/Cat/0/Board/UBB55
Hope this helps. I check in here every once in a while so if I can be of additional help, let me know.
Cheers,
Doug