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Comcast recently convinced me to upgrade from a internet only package to a internet + limited basic cable package, which with the promotional discount was cheaper than just internet. Comcast limited basic cable is relatively useless. I get channels 2 through 33, most of which are not english channels, and are not in HD. When the promotional period expires, I plan on cancelling cable and keeping only internet.
About 2 years ago, I had used a VERY OLD set of rabbit ears to get FREE HDTV channels, which worked well for basic channels. The unit was compartively large (approximately 1 ft x 1ft x 1ft footprint plus two rabbit ear antennas) and the signal would often times cut in and out. Despite getting FREE HDTV channels, I eventually discarded the antenna due to its unstable connection and large footprint.
I now purchased the Homeworx HW110DTV Flat Antenna (buy online). With the same coaxial cable connection to the TV, all that remains is a cable and what literally looks like a piece of cardboard. There is no base unit or antenna ears (like my previous set of rabbit ears). In Sunnyvale, CA, the connection is very strong, with the most popular basic channels never cutting in or out. The follow are the FREE HDTV channels I receive and regularily watch (unfortunately, I live too far from the broadcast towers to receive NBC):
FOX (2.1) - strong signal
KRON 4 (4.1) - weak signal
ABC 7 &7.1) - strong signal
All in all, purchasing an antenna is a great investment. I purchased the Homeworx HW110AN HDTV Flat Antenna for $7.99 + tax + free shipping = $8.71. Without a doubt, Comcast cable must be costing more than $8.71 per month! For those who live further north of Sunnyvale (closer to San Francisco), you are likely to receive more channels with a stronger signal.