Hi, and welcome! It's not an inadequate antenna for your area, that's for sure. Check the following, in order of increasing complexity:
* Verify that your tuner is set to receive over-the-air (OTA) signals. Many HDTVs/tuners are set by default to cable or satellite service, which is on a different standard from OTA. Consult the instructions for finding this function in the setup menus; with many tuners, you select "air," "antenna," "terrestrial," "OTA," etc.
* If you selected OTA in the previous step, the tuner needs to scan the airwaves for all available channels before you may tune them. This function is also in the setup menu. Scanning is automatic once launched; it should take just a few minutes to complete.
No love yet? Try:
* Verifying that the antenna is pointed towards San Francisco. Sutro Tower is the location for your network affiliates' transmitters. The antenna's "vees," both horizontal and vertical, should be open in that direction. If they're not, the antenna is incorrectly aimed. It's a very common mistake when setting up a new antenna.
* Double-checking all coaxial-cable connections, and making sure there's no apparent physical damage to the cabling. This includes dents in the insulation jacket from excessive bending, crushing or pulling. Replace any cable with such damage.
* If nothing's done the trick up to this point, replace the balun up at the antenna. Like any other part, baluns can be bad right out of the box.
IOW, this is basic troubleshooting. One last note: If the problem was with the antenna, cabling or balun, be sure to re-scan for channels after you've corrected the physical problem(s). Good luck!