This is the KDKA History section of
The Broadcast Archive
Maintained by: Barry Mishkind - The Eclectic Engineer
last update: 10/1/06
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.