Watching free TV over an antenna seems so out-of-date that it’s hard to believe the technology can change any more. But it can, and it is.

Specifically, channels 7 and 38 out of Boston will shift frequencies by the end of the week.

To keep watching them free over the air, you’ll need to re-scan your television so that it associates the new frequency with the existing channel. (Cable systems and satellite dishes are not affected.)

Rescanning should bring the station back but if you’re on the fringes of the broadcast area you might encounter some problems. This happened to a number of people last time this was done with Boston stations, judging from reader comments I received last time I wrote about this.>kern 0pt<

Plenty of people still use TV antennas, by the way. In 2019, the ratings company Nielsen estimated that 16 million homes watched at least some programs via free TV – a number that had gone up in recent years because of over-the-air streaming.

These channel changes are all part of a multi-year shuffling of channels being done to take some of the airwaves once used by analog television, no longer necessary after we switched to digital broadcasts, and use them for 5G and other mobile applications. The Federal Communications Commission sold off frequencies worth more than $19 billion to telecom firms and, all told, about 1,000 TV stations had to move frequencies. That includes about a dozen major Boston stations.

What this means is that spectrum once used to broadcast “My Mother the Car” on Tuesday nights will now be used to let us watch “My Mother the Car” on our phone via YouTube even when it isn’t Tuesday. Such is progress.

By the way, this is different than what is being called “NextGen TV,” more formally known as ATSC 3.0. These are a series of voluntary software and equipment upgrades that should allow more personalization, high-definition viewing, and interactivity. TV sets are starting to be made ready for ATSC 3.0, but it hasn’t been rolled out yet.

Back to shifting channels. As explained to me by Jean Kiddoo, chair of the FCC Incentive Auction Task Force, some viewers may have problems after shifts because broadcast antennas are more complicated than I thought. (If you want to learn more, check their website: https://www.fcc.gov/TVrescan?utm_source=Pitching&utm_medium=EarnedMedia&utm_campaign=FCC-Rescan)

“Antennas are very specifically geared toward specific frequencies. Most were put in place during DTV (digital) conversion of 10 years ago, tuned to a particular frequency,” said Kiddoo. “So they need a new antenna and a new transmitter.”

“To take down a 17,000-pound antenna from the top of one of those towers is a major, major effort. … In some cases … they have gone onto what we call interim antennas, while they do work on their main antenna they need to continue to broadcast while they take the old antenna down, put a new antenna up,” Kiddoo said.

Since interim antennas are usually lower on the tower, the signal may not penetrate quite as far out.

“Your readers are not as close to Boston so interim antennas may have been affecting them,” she said. “There are still a couple of stations in Boston on interim antennas.”

The shift began in 2018. “This is part of a three-year transition to package TV stations across the country. There are 10 phases altogether, and this is completing phase 7, so we’re about 70% done,” said Kiddoo.

It wasn’t done all at once because of interference concerns. “For example, if we want Channel 2 to move to Channel 4, there is already a station in Channel 4 which had to move first.”

It appears that WMUR, the station’s dominant TV station, will not have to move. Some smaller New Hampshire stations are moving, including ConcordTV community access and a Merrimack-based Telemundo channel.

All channels should have changed by July 2020. If you lose access to a channel you once could see, Kiddoo rec ommends to check the station’s website or call them, to see if they’re on an interim antenna, or just rescan every now and then.

Or check YouTube. That Jerry Van Dyke, he was a riot!