July 9-16, 2004

Prudential Tower, Boston

It's not quite the tallest building in the city - that honor goes to the nearby John Hancock Tower by about 40 feet - but the Prudential Tower in Boston's Back Bay is without a doubt the most significant skyscraper transmitter site in New England.

The Pru went up in 1964, and it was almost immediately put to use by broadcasters. The Archdiocese of Boston put WIHS-TV (Channel 38) on the air here in October of that year, and the TV station would remain a tenant for another eight years, most of that time under its new calls of WSBK.

FM radio came to the tower a few years later; as best we can figure out the timeline, WBCN (104.1) was the first FM station up here, eventually moving its studios into the penthouse level of the building as well. WCOP-FM (100.7) and WWEL-FM (107.9) joined the rooftop crowd sometime in the seventies, moving from the towers of their sister AM stations, WCOP 1150 in Lexington and WWEL 1430 in Medford. Emerson College's WERS (88.9) spent most of the seventies and eighties up here before moving to One Financial Center in the nineties, and in 1981 the roof also became home to WMJX (106.7), the former WBZ-FM (relocating from the WBZ-TV tower in Needham, which we'll examine in depth next week.)

Around the time of WMJX's arrival on the roof, the tower sprouted a master antenna, the six-bay panel you now see just below the first level of guys. The master antenna was - and still is - home to 100.7, 104.1, 106.7 and 107.9.

The TV antenna at the top of the mast has a story of its own: after WSBK departed the Pru in the early seventies, moving to the new candelabra tower in Needham, its space - including the transmitter room just down the hall from the swanky "Top of the Hub" restaurant was eventually taken over by new sign-on WQTV (Channel 68).

Much more recently, Greater Media (which owns WMJX) has relocated three more of its FM stations to the Pru from the "FM 128" tower in Newton. WTKK (96.9 Boston), WBOS (92.9 Brookline) and WROR-FM (105.7 Framingham) now use that ERI panel antenna mounted below the second set of guy wires.

There wasn't much room in the mechanical room at the top of the building by the time the new FM facilities came on here (in fact, while WBCN and WZLX have rooms of their own, WXKS-FM 107.9 has to settle for a chain-link cage exposed to all the heat and dust of the building's machinery) - so Greater Media put its FM stations in a series of metal containers outside on the roof, set back just enough so that you'd never notice them from street level.

Shown above and at left is the "double-wide" (actually, double-long) that's home to WMJX and WROR. Around the corner sit two individual containers that house WTKK and WBOS.

At right, you can see the narrow space between the containers and the mechanical room atop the building - and back there on the northeast corner of the building, the auxiliary FM antennas atop a short tower.

But since our tour guide for the day was Greater Media chief engineer Art Pepin, let's go back and have a closer look at his transmitter rooms, shall we? You can see a typical configuration above - each station has two Broadcast Electronics FM-20B transmitters for analog use. (They're rotated seasonally, so there's not really a "main" and an "aux" so much as a "summer" and "winter" transmitter.)

Greater Media's been pioneering IBOC digital in the market, too. Each of the four stations here now has a BE FSi 10 encoder and FXi 60 exciter for its digital transmissions.

(Greater has a fifth FM in the market as well; WKLB 99.5 Lowell also has IBOC at its transmitter site on Wood Hill in Andover.)

All four of the IBOC signals are combined at low level into the lower of the two antennas - and if you've been paying careful attention, yes, that means WMJX is using separate antennas for analog (upper) and digital (lower). That required special FCC permission, though with WMJX as a test case, the Commission is now allowing such separate-antenna configurations as a matter of course.

In addition to consolidating its transmitters at the Pru, Greater Media consolidated its studios at a new facility on Morrissey Boulevard in Dorchester a few years ago. In the southern view below, you can see the dishes for the 5.8 GHz spread-spectrum microwave link pointing back towards the studios, carrying eight T1s worth of data (four primaries and four backups.)

(There's an irony here, too, at least where WROR is concerned - all through the eighties and nineties, in its WVBF/WCLB/WKLB days, 105.7's studios were right here on the 13th floor of the Pru! WZLX still has its studios here, on the 24th floor, and WEEI was here on the 44th floor all through the seventies and eighties.)

Before we climb the ladder to the upper roof level and get a good look at the base of the tower, a few more shots of the beautiful views we enjoyed this fine May day. To the east, we see I.M. Pei's John Hancock Tower and H.H. Richardson's Trinity Church just to its left (look for the red room overlooking Copley Square). To the right of the Hancock (whose sole broadcast tenant is translator W267AI), we see One Financial Center (home to WERS 88.9 and WHRB 95.3). Off in the distance, to the left of the Hancock, the reddish skyscraper of One Beacon Street is home to WMFP-TV 62.

(And perhaps you've heard the old joke about the best aspect of the view from the Pru - that it's the one spot in Boston where you don't actually have to look at the Pru?)

One more rooftop view: here's what it looks like to the west, dominated by the Mass Pike Extension that actually passes directly beneath the Pru. That's Fenway Park at the left, and in the haze off to the right you can just make out Boston University astride Commonwealth Avenue. Somewhere in there is the old WBUR (90.9) tower. (It was, alas, too hazy to get a good view of the WBZ complex out on Soldiers Field Road...)

Those of you who are connoisseurs of FM master antennas (hey, somebody's gotta be, right?) may by now be wondering where the combiners are - and therein lies an interesting story.

Instead of building a separate room for the combiner that feeds the lower antenna, Greater Media worked with ERI to put separate combiner modules behind each of the individual transmitters. I believe this is WTKK's piece of the combiner at left.

And now we can head for the upper level of the roof, where we clamber over the various holes and protrusions (including the airshaft that plunges 52 stories down through the center of the building) to get to the base of the tower itself.

The tower now rises 157 feet above the roof, which brings us to 907 feet above ground at the tip of the channel 68 antenna. It certainly dwarfs Art, in the yellow shirt near the base!

(And again, our thanks to Art for taking the time to show us all around this fascinating site!)

A few more miscellaneous notes from up here: WTMU-LP (Channel 32) also calls the Pru roof home, providing Telemundo programming to Boston (and serving as the originator for the programming also seen on WNEU, channel 60, in Merrimack, N.H.) And channel 68, now Pax's WBPX, uses stacked Yagi antennas mounted on the edges of the roof to monitor the signals of its satellite stations, WDPX (Channel 58) on Cape Cod and WPXG (Channel 21) in New Hampshire.

Next week, we'll continue to examine the digital broadcasting future in Boston - this time on the video side, at the WBZ-TV tower in Needham. See you then!

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