Next Monday, some Bay Area customers can expect to see a "no signal" message on their TV.

Those customers will need to re-scan their TV or converter box to keep watching local stations following the installation of new antennas on Sutro Tower. Those who get their signal over the air will need to re-scan manually when channels switch to new frequencies on Monday at 10 a.m.

While cable and satellite TV customers will also be affected, they don't have to re-scan, Sutro Tower Inc. spokesperson Dave Hyams said. "80% use cable or satellite and they do it for you," he explained. But "20% are over-the-air customers," and they will need to re-scan.

As we reported last November, eagle-eyed Hoodline readers noted that a mast atop the 977-foot-high steel tower suddenly went missing. The tower is undergoing a major upgrade in order to add several new broadcast antennas as part of the Bay Area’s portion of the nationwide broadcast spectrum repack program.

According to a video posted on Sutro Tower's website, over 100,000 pounds of steel was removed from the tower during the work on the antennas and the design process for the upgrades took three and a half years. Work has to be precise to protect surrounding homes, as no tools or equipment parts can be dropped.

Sutro Tower with a missing mast last year. | Photo: Razmig H./Hoodline Tipline

The initiative makes additional frequencies available to broadband users, making room for the rollout of 5G technologies. The changes are necessary as 30% of bandwidth previously used by TV stations are now shifted to those wireless services.

The new TV antennas are mandated by the Federal Communications Commission. Antennas and other needed equipment come from broadcast manufacturer Dielectric. While each station needs its own antenna, it's possible to stack them on top of each other without signal interference.

Hyams said nine TV stations in total will be affected. However, only half of them will change their frequencies on Monday. The remaining ones will follow on April 29 at 1 p.m., when over-the-air customers will need to re-scan again.

When one station is changing the signal, the others have to follow. "It's a domino effect," Hyams explained. "The rollout has been going smoothly nationwide," he said, adding that he believes "it's a pretty straightforward process".

Hyams notes that with the antenna upgrades, Sutro Tower is also getting strengthening of some structural elements of the tower to meet the current building code, including new wind resistance requirements.

"It was a complicated process," Hyams said, adding that work will continue throughout 2020. It will probably be completed "at the end of the year," he said. Until then, neighbors will see workers going up and down on the tower taking care of new guy wires, nuts, bolts and other necessary equipment.

To learn more about how to re-scan your TV, visit Sutro Tower's website.