This is the KDKA History section of
The Broadcast Archive

Maintained by: Barry Mishkind - The Eclectic Engineer
last update: 10/1/06

KDKA

Many people know KDKA was "the first broadcast station."  That is, however, more a result of the Westinghouse PR Department than reality. In the 1920 era, when KDKA received its "limited commercial" license, commercial licenses were common. ALL the telegraph stations were "commercial" ... which meant they sold services - sending messages - to others. 

There is material elsewhere on this site describing the beginnings of KDKA, WHA, KQW, WWJ, and others. Not well known is that KDKA did NOT broadcast the famous election returns in 1920, tie was known as 8ZZ that night, because authorization for KDKA has not yet arrived. No matter, KDKA definitely is one of the pioneering stations in the industry ... perhaps not the first, but among the firsts.

From Art Reed: an NAB paper from ~1995 that describes both the new and old KDKA antennas, and the process they followed to arrive at the decision to build the new antenna. 

In brief, the original (ca. 1929) antenna was 720 feet tall, with base insulator and center insulators at 360 feet. It was center-fed by a balanced-wire arrangement, which was in turn fed from a "spider coil" balun at the base of the tower. Due to high-angle radiation coming down about 25 miles out, in 1939 they moved the tower to its current Allison Park site (closer to the city) and built the building that houses the current transmitter site.

The "spider coil" was rebuilt several times over the years, but there was never a way to predict or control its effect on the bottom half of the tower, being effectively shunted across the tower base. In 1995, they tore town that tower due to age, and built the current tower.

It is a base insulated, sectionalized tower, also 720 feet tall. The sectionalization occurs at 270 feet, making the tower 1/2 wave over top of 1/4 wave, roughly. Two 3-1/8" transmission lines , lighting conduits and antenna monitor leads are 1/4 wave stubbed onto the tower, in order to cross to the top section, and to feed the tuning box, which is at the 270 foot level, complete with motorized components. There are sample loops at the current maxima points of each section connected to an antenna monitor to adjust the phases and amplitudes of the current in each section. There is  also either a series or parallel resonant circuit going from tower base to ground that is there to aid in the adjustment of the current in the bottom section of the tower.

The design was done by the late "Bix" Bixby, and I believe Ogden Prestholt was somehow involved in the design as well.