Site of the Week 3/26/2021: Boston’s Cabot Street Tower

Text and photos by SCOTT FYBUSH

The DTV repack that ended last year caused a lot of physical changes at TV towers all over the country, but few were as complex as the dance that Boston’s major TV stations had to go through to prepare for the next chapter in that market’s broadcast history.

In the analog days, it was relatively simple: three of Boston’s four VHF stations shared a tower on Cedar Street in Needham that had been built in 1957 for WBZ-TV (Channel 4). WGBH-TV (Channel 2), the PBS station, and WCVB (Channel 5), the ABC affiliate, came along later as tenants, as did WGBH’s sister station WGBX (Channel 44). A mile or so to the southeast, across Route 128, a Stainless candelabra tower that went up at the end of the 1960s was crowned with a candelabra that carried the city’s three big UHF stations – eventual Fox affiliate WFXT (Channel 25), WSBK (Channel 38) and WLVI (Channel 56).

The DTV conversion in the 2000s changed things only slightly: the Cedar Street tower was rebuilt in taller form and added WSBK to its mix, while the candelabra on Cabot Street remained home to WFXT, WLVI and eventually to a backup facility for several of the market’s big FMs.

Then came the repack, and some bigger changes: WLVI was by then a sister station to WHDH (Channel 7), and it chose to sell off its UHF spectrum and channel-share with WHDH just across the city line over at WHDH’s big self-supporter in Newton. WGBH also grabbed a share of the repack auction money to be had, by moving from UHF to low-band VHF on channel 5. That left only WFXT as a main UHF tenant at the Cabot Street candelabra, and it created an opportunity for all the stations and for their landlord, American Tower: it could remove the old UHF antennas on the candelabra arms (using a new aux site for WFXT over at Cedar Street to keep Fox on the air during the rebuild), and then build out a new combined UHF facility using a single antenna atop the tower itself, adding a big low-band VHF antenna for WGBH at the top of the stack.

The result, when it was all done, would be a new primary facility for WGBH and WFXT and a full-power backup for WBZ-TV, WCVB, WSBK and WGBX, providing the ability to do a comprehensive replacement of the main antennas for those stations over at the Cedar Street site.

Where to put everybody? That part turned out to be easy: when the Cabot Street facility was built out in the early 1970s behind the Sheraton Needham hotel, each of the three big UHF stations had its own big brick building surrounding the tower base. WFXT stayed put in its building all the way through, WSBK’s became (at least in part) the FM auxiliary site – and WLVI’s building, closest to the hotel, was left completely empty when that station began channel-sharing down the road with WHDH-TV.

The last time we’d been in this room, just before the analog shutoff in 2009, it was a big concrete-block cavern with one long line of transmitters for WLVI’s analog channel 56 and its DTV signal on RF 41. A decade later, it had been completely transformed, with brighter lighting, new walls and flooring, and five transmitters in the space that had once been used by just two.

WGBH’s main transmitter, a Comrex, and WGBX’s auxiliary rig, a Rohde & Schwarz, face each other at one end of the room, next to a walled-off space for engineering offices and a rack room for WGBH (this is, after all, the main site for their main WGBH signal.)

The other auxiliary tenants fill the rest of the room: CBS now owns both WSBK (repacked to RF 21) and WBZ-TV (repacked to RF 20), both on GatesAir transmitters, and there’s another GatesAir back here for WCVB, repacked to RF 33.

All those liquid-cooled rigs make for a quiet, cool room – and for a lot of plumbing and heat exchangers to move the coolant around.

There’s a big combiner at the far end of the room, handling not only WBZ, WCVB, WSBK and WGBX when they’re on their aux rigs here but also the full-time needs of WFXT (repacked to RF 34), which had to run new transmission line from its building across the parking lot over here to feed the combiner and the main line up to the antenna.

(We visited WFXT’s room in 2013, and profiled it as part of a deeper look at the candelabra here on Site of the Week in 2014.)

You can see the RF setup here in much more detail over at Mike Fitzpatrick’s NECRAT.us site, which also has great pictures of the helicopter pick that took down the old antennas and lifted the new ones. And one more bit of trivia – the UHF signal coming from the WGBX transmitter is carrying more than PBS. It adds NBC to the mix here, since NBC’s WBTS-CD, aka “NBC 10,” is a channel share on WGBX’s RF 32 signal, and so all of the Big Four networks plus PBS end up having signals from this site.

As it’s turned out, this site has been on at full power fairly frequently since it was completed in 2019, making a solid case for the economic value of building out a full-power, off-site aux for a big-market station that can’t afford to be off the air very long.

In addition to keeping WBZ, WCVB, WSBK and WGBX/WBTS on the air during the antenna changes over at Cedar Street, the Cabot Street site has been in use on several occasions during repairs to the transmission system at the main site, keeping Boston’s biggest TV stations broadcasting smoothly even when things have been hectic behind the scenes.

Thanks to Mike Fitzpatrick for the tour!

And don’t miss a big batch of Boston IDs next Wednesday, over at our sister site, TopHour.com!

Next week: Artifacts from the former Newseum