Sept. 25, 2009

KDKA 1020, Pittsburgh, PA

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This week's installment comes to you from the NAB Radio Show in Philadelphia - but our featured site is 300 miles across the Keystone State in Allison Park, Pennsylvania, just up Route 8 from Pittsburgh. And fittingly, the site of KDKA (1020) is the November page in the 2010 calendar, since November 2, 2010 will mark the ninetieth birthday of this pioneering radio station.

The earliest physical remnants of KDKA have disappeared in recent years: the brick garage in Wilkinsburg where Frank Conrad put amateur station 8XK on the air after World War I was demolished a few years back to build a new Wendy's (sigh), and the Westinghouse plant in East Pittsburgh where 8XK famously became KDKA is gone now as well.

KDKA didn't stay in East Pittsburgh for long; its next stop was in Forest Hills, near East Pittsburgh, where its first 50 kW transmitter site, circa 1927, is now the Westinghouse Recreation Center. After three years in Forest Hills, KDKA again uprooted, this time for a site in Saxonburg, Butler County, far to the north of Pittsburgh. At Saxonburg, KDKA experimented with shortwave broadcasting, with medium-wave power levels as high as 400 kW (under the experimental call W8XK) and with several antenna designs that were complex (and apparently unsuccessful) prototypes of today's low-profile antenna designs, such as the Kinstar and Paran antennas.

After an unsuccessful attempt at a vertical tower in 1936 ended in collapse, KDKA put up a new tower at Saxonburg in the fall of 1937 - a 710-foot center-fed vertical radiator that could broadly be classed as being in the Franklin family of antennas. (A true Franklin is a half-wave over a half-wave, while KDKA's tower was a little shorter - 135 degrees over 135 degrees.)

In a bid to improve signal strength in Pittsburgh, Westinghouse moved the Saxonburg tower in 1939 to the present tower site in Allison Park, about a dozen miles closer to downtown. The Saxonburg site remained in use for shortwave (under the W8XK calls) until the end of the war, and was eventually donated to the nuclear physics program at the Carnegie Institute of Technology (now Carnegie Mellon) for the construction of a cyclotron. (After the cyclotron was dismantled in the 1970s, the Saxonburg site became home to the high-tech firm II-VI Corporation, which remains there today.)

KDKA's new transmitter building at Allison Park was a near-duplicate of two other Westinghouse sites from the same era, WBZ in Boston and KYW in Philadelphia - but while WBZ's building in Hull, Mass. was done up in New England clapboard and KYW's in stone, KDKA's was built of local brick.

At this site, unlike WBZ and KYW, there's still an original transmitter to be seen: entering the main transmitter hall from the front door, the entire left side of the room is still taken up by the mammoth Westinghouse 50HG transmitter, complete with original control console. (I have heard - but have not confirmed - that this transmitter was actually designed to do 100 kW, had the FCC allowed it; KDKA's application for 500 kW that was filed in 1936 was dismissed at Westinghouse's request in 1938.)

The Westinghouse was eventually joined by a pair of Gates MW50s in the 1970s, which eventually gave way to Harris DX50s and 3DX50s - and it's been many years since the Westinghouse ran. (There's an interesting story, possibly apocryphal, about how the Westinghouse gave its last performance on the night the Pirates won the 1979 World Series, when vandals shorted the tower base - and while the MW50s couldn't operate into the shorted tower, the Westinghouse saved the day, running at very low efficiency. If it's not true, it should be...)

Behind the main transmitter room is an engineering shop, where engineer Roy Humphrey shows off an unusual air monitor: a crystal set, blasting away loudly from the workbench, complete with IBOC hiss.

There's a garage on the north side of the building, and on the south side are rooms that once housed engineers and today are used for storage.

Down in the basement are the vaults where the rectifiers and power transformer for the Westinghouse once sat; today, it's used for storage, including some interesting relics of the old KDKA-FM stacked in a corner.

With KDKA's main studio in the very urban Gateway Center complex in downtown Pittsburgh, this site was a natural location for satellite receivers and uplinks for both the radio station and sister station KDKA-TV, and a separate building on the property houses those functions, with microwave links back to the downtown studios.

And that brings us out to the tower, which sits in a big clearing at something of a distance from the transmitter building. The tower that's on the site now is not the 1937 original; that tower was removed in 1994 (with a portion of one tower leg cut into slices that were encased in Lucite and sold to benefit Pittsburgh's Children's Hospital) and replaced by the current tower, which is 718 feet tall and, like its predecessor, is sectionalized.

The unusual design was meant to reduce adjacent-channel interference to sister stations WBZ and WINS, and there's been considerable debate in engineering circles about its effectiveness. (It was apparently a challenge to make this tower work for HD Radio, and KDKA operated under STA at 35 kW for a time as a result.)

Thanks to Roy Humphrey of KDKA for the tour!

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