Monday, April 28, 2014

Music from The Tower Building Part 2

The KAAY-KLPQ studios on Cottondale Lane were uniquely located so that
it was impossible to provide a line-of-sight link to Wrightsville
(KAAY) or to Shinall Mountain (KLPQ). Fortunately, The Tower Building
had a good view of Shinall Mountain and a somewhat less good view of
Wrightsville. To deliver the audio signal to both transmitters, both
KAAY and KLPQ used equalized phone lines from the Cottondale Lane
studios to The Tower Building, with STL links (for Studio-Transmitter
Links, commonly called microwave links) from The Tower Building to
both Wrightsville and Shinall Mountain. Although the system
undoubtedly worked fine when it was installed, the equalized phone
lines had deteriorated over the years. My predecessor had ordered and
installed new STL links from Cottondale Lane to The Tower Building for
both KAAY and KLPQ but had not been able (or didn't have time) to make
them work properly.

As Dave T. has observed, KAAY used equalized phone lines from the 7th
Street studios to Wrightsville. It takes a lot of careful telephone
company engineering to make a low-fidelity telephone line carry a
broadcast-quality audio signal. Although I don't know for sure, I
suspect that the original KAAY telephone company program lines were
step-equalized between the 7th Street studios and the Franklin
exchange office, then equalized from the Franklin office to the office
serving Wrightsville (I forget the name of the exchange), and then
equalized from that office to the Wrightsville transmitter. Careful
telephone company engineering and sturdy Western Electric equipment
gave KAAY a very nice audio signal.

Over the years, much of this telephone company engineering expertise
has been lost. The telephone company has found ways to stack many
different telephone calls on a single pair of wires, meaning that a
dedicated broadcast audio circuit on a dedicated pair of wires was
wasteful and expensive. The telephone company responded by breaking
the broadcast audio signal into separate pieces, sometimes routing
these pieces over different paths, and reassembling them at the end. 
This produces some weird audio effects. Even worse, we could hear
Tower Building elevator noise on both KAAY and KLPQ, something that
should not happen on a properly balanced circuit.

Although the STL transmitters at the Tower Building (one for KAAY to
Wrightsville and two for KLPQ to Shinall Mountain) worked OK, it was
very difficult to operate 3 STL receivers and three STL transmitters
in the same band in close proximity to each other. To make matters
worse. my predecessor had installed all of this equipment in the same
rack and had installed braided coaxial cable to the receivers that
leaked like a sieve. After replacing these coaxial cables and
constructing a shielded room in the former KMMK studio room to house
the STL receivers and grounding everything to the steel frame of The
Tower Building, I finally got the system to work reasonably well. 
However, The Tower Building was the common point for all audio and
transmitter control signals for both KAAY and KLPQ and was a constant
source of trouble. I recall one afternoon when Tom Rusk inadvertently
unplugged an extension cord and put both stations off the air during
afternoon drive time.

As best I can tell, The Tower Building site is no longer in use. The
FCC files for KKPT do not list an auxiliary transmitter at The Tower
Building. The KKPT STL system now reaches Shinall Mountain through a
relay at the former KLRA transmitter site at Galloway, east of North
Little Rock, and KAAY now uses an STL from its West Little Rock
studios to Wrightsville. It appears that the original KMMK studio and
transmitter site have now been lost to history.

Hollis Duncan

(Sorry, I forgot to add the picture of the Tower Building Hollis sent me...here it is...Bud)

No comments:

Post a Comment