According to historical information from
mediumwave station KDKA in Pittsburgh, Pennsylvania, Dr. Frank Conrad made his
earliest observations regarding the propagation of radio signals in the
shortwave spectrum during the year 1920.
What he observed was that harmonics from longwave and mediumwave
transmitters often propagated with a better signal and wider coverage on shortwave than was available from
the fundamental longwave or mediumwave signal itself. This phenomenon led him to begin a serious
study of the possible advantages to be obtained with deliberate transmissions
in what has since become the shortwave bands.
A few months later in the early
Spring of the following year 1921, Conrad began experimental transmissions from
his own home grown amateur station 8XK on the second floor in the family garage
at the corner of Penn and Peebles
streets in Wilkinsburg. His experimental
transmissions on 100 meters provided good reception at amateur stations of
friends in Boston.
Then in 1922, Conrad directed the
construction of a 1 kW shortwave transmitter at the Westinghouse factory
complex in East Pittsburgh. In August,
this new transmitter was installed in the wooden shack on top of the eight
storey Building K where it was taken into experimental service under the
callsign 8XS.
Black and white photographs taken
during this era show that this wooden shack was located on top at the western
end of Building K, and building K itself was the southern most tall building in
a small cluster of equal height high rise factory buildings in East
Pittsburgh. At the time, the mediumwave
transmitter for KDKA was also still located inside this roof top shack, and the
shortwave antenna for 8XS was affixed to the same flat roof top.
The shortwave antenna for the transmissions
on 100 meters (3 MHz) was 40 ft long with a height of 35 feet above the roof
top. The flat top antenna consisted of
apparently 5 parallel wires that were end fed at the western end from a two
wire open feed line. The program feed
for experimental transmissions from 8XS were taken from the regular scheduling
of KDKA on mediumwave.
Beginning on March 4 of the next
year (1923), station 8XS began a daily program feed on shortwave to a new
mediumwave station, KDPM, located at another Westinghouse facility in Cleveland
Ohio. This program relay from KDKA was
on the air for several hours every evening.
Then, eight months later on November
22, the KDKA mediumwave programing was relayed on shortwave to another
mediumwave station, this time KFKX at Hastings Nebraska, near the geographic
center of the continental United States.
Station KFKX fed this program stream into two transmitters; mediumwave
for local coverage and shortwave for pickup and local mediumwave coverage in
California.
The shortwave relays from 8XS in
East Pittsburgh to the two distant mediumwave stations, KDPM Cleveland and KFKX
Hastings. was discontinued soon afterwards due to the poor quality of the
retransmitted programing.
In July 1924, both the mediumwave
and shortwave facilities of KDKA were transferred from the factory roof top in
East Pittsburgh to another Westinghouse facility, this time on Greensburg Pike
in Forest Hills. At this new location,
just one mile distant from the original East Pittsburgh location, a separate
single story brick and concrete transmitter building was constructed.
Transmitters for both mediumwave and
shortwave were installed, and a 50 feet long copper tube was attached to a
wooden pole as the antenna for the shortwave transmissions. At this new location, the shortwave callsign
8XS was relinquished, and the license for Conrad’s internationally known personal 8XK callsign was
transferred to Westinghouse.
In April 1928, one international
radio columnist described the shortwave signal from KDKA-8XK on 26 meters as
very sharp and difficult to tune, and on 62 meters as strong with garbled
modulation. During this same year,
international radio regulations promulgated in the United States required the
insertion of the letter W as the first letter in the callsign, and thus 8XK
became W8XK.
In an endeavor to improve mediumwave
signal coverage into the main population areas of Pittsburgh, another move was
staged in 1931. A huge new station was
constructed on a site in Saxonburg, after a total of 62 different sites in the
greater Pittsburgh areas had been examined and tested.
In honor of KDKA and as a welcome to
their community, the local civic officials changed the name of the highway on
which the station would be built to KDKA Boulevard. Previously various stretches of this highway
were gazetted under different names.
However, give a year or two later, and KDKA Boulevard was re-gazetted as
Saxonburg Boulevard.
A new transmitter building was
constructed at Saxonburg on a property of 130 acres and four new shortwave
transmitters at a power level of 40 kW each were constructed on site. The mediumwave KDKA transmitters were
installed in the north end of the building, and the shortwave transmitters were
installed in the south end.
It was stated at this stage, that
the huge new 400 kW super power mediumwave transmitter was rated at the very
strange reckoning of 500 horsepower; that the very first KDKA transmitter 11
years earlier weighed just 500 pounds; and also that the combined weight of all
of the mediumwave and shortwave transmitters at the new Saxonburg site in 1931
weighed a staggering 164 tons.
(AWR-Wavescan/NWS 370)