InBroadcast - InReview 2022 - 60

60
www.inbroadcast.com | Vol: 12 - Issue 12 | InReview 2022
InTech
Dielectric Upgrades Stacked
Antenna Array for TV Stations
at Telefarm Towers Site
Leading over-the-air supplier designs its " most mechanically unique " antenna in its
80-year history for WUCW-DT, replacing the lower-position antenna with an innovative,
highly reliable end-fed Pylon system...
D
ielectric announces that WUCWDT,
a CW affiliate serving the
Minneapolis-St. Paul market, is
now on the air with a new Dielectric
UHF antenna that
traditional
stacked
challenging
design and brings simplicity and longterm
reliability to the broadcaster.
The
E-Type
design addresses
code requirements
current
reevaluates the
antenna array
antenna
tower
for exposed
transmission line and was delivered
in a modular configuration that
simplified the antenna replacement
project
for
Tower King II, which
managed all site preparation and
installation work. The carefully
engineered
the existing Dielectric
antenna on the top position
without
requiring extensive
tower modifications.
WUCW shares space with several
broadcasters on the south tower
at
transmission site for TV and FM
radio broadcasters.
To optimize
tower real estate and provide true
omnidirectional performance for their
viewers, WUCW and ABC affiliate
KSTP-DT have long transmitted from
a top-mounted broadband stacked
antenna system. The original system
included a Dielectric
TU Series
Deltastar panel antenna on the lower
position of the stacked
array.
WUCW's
existing
Deltastar antenna was
a " five around panel
antenna " configuration
supported by a very
wide and
robust
mast. When the time
came to replace the
antenna, Dielectric
knew that they were
about to face one of
the most challenging
design projects of the
company's lifetime.
Telefarm Towers, a two-tower
system also retained
repack
" WUCW engineers first considered
making an adapter for the top
antenna and the existing support
system, but changed course toward
preferring a modernized
stacked
array that was simpler and provided
enhanced long-term reliability over
the panel system, " said James Butts,
Mechanical
Engineer, Dielectric.
" While that was indeed the result,
the work required to get there made
this one of the most mechanically
unique UHF antennas we have
manufactured. This WUCW antenna
is a very large variant of our E-Type
antenna design that was carefully
engineered to meet the customer's
unique design needs. "
Design Challenges
and Innovations
One of many challenges was how to
run the transmission line to the top
KSTP antenna. Previous revisions of
design codes allowed Dielectric
to
run the line up the side of an antenna
mast, exposed
without
increasing the mast
to the elements
drag
coefficient.
" The latest code revisions required
by Telefarm impose mast designs
with exposed appurtenances such
as
to come
system
design
transmission line with higher
drag coefficients, which greatly
increase wind loads, " said Butts.
" We had
up with an antenna
feed
that would obscure
the transmission line
without
increasing
the windload on the
bottom antenna. That
meant
routing
the
feed to the top KSTP
antenna under the
radome of the bottom
WUCW antenna. "
Dielectric
Telefarms Stacked
Antenna Array
Dielectric
designed a two-piece
mast for WUCW that measures
twenty inches in diameter and is
two inches
technology
is
thick. Groundbreaking
utilized under the
hood of this antenna to verify WUCW
has
an omnidirectional
patterns.
azimuth
pattern in both the horizontal and
vertical
Typically, the
azimuth patterns are distorted on
a bottom of a stack antenna due to
the transmission line to feed the
top. This, along with the mechanical
stoutness of the antenna, makes this
a truly innovative achievement by the
Dielectric team.
Modular Installation
To make Tower King II's job easier,
Dielectric
split the new bottom
antenna into two pieces, adding a
flange in the middle. That allowed
the tower crew to raise the antenna
and split the lifting load on the tower
and gin pole as the total antenna
weight was close to 30,000 pounds,
and later connect the two pieces
using the carefully positioned flange.
" The biggest
challenge
mechanically was to keep the weight
of those two sections low enough
for a potential helicopter lift or a
reasonably
sized
ginpole, " said
Butts.
Kevin Barber, Owner and President
of Tower King II, confirms that the
Telefarms Tower Site WUCW Stack, Left Tower
replacement work was among the
most unique of his career.
" The
original
Deltastar
antenna
was 32,000 pounds with a very tight
guide path, and that made it very
challenging to bring the antenna
down with a ginpole without
bouncing off the tower, " said Barber.
" That
basically
requires walking
the entire antenna down the tower,
which is fairly difficult. We inserted
a stabilizing frame between the two
antennas, and then jumped the
ginpole down to secure the Deltastar
and begin the process of walking it
down. "
The combined
weight
still
of
the
new Dielectric antenna is several
thousand pounds lighter than the
Deltastar, but would
require
a ginpole to lift it as one piece. By
splitting the new antenna into two
sections, Dielectric gave Tower King
II the option of using helicopters
over ginpoles to lift the new WUCW
antenna into place.
" We
set
the
first
section
and
then the second section, and then
connected
the bottom and top
antennas with the transmission line, "
said Barber. " In the end, the thought
that Dielectric put into the design and
the modularity made the installation
very clean and easily achieved. "
https://www.dielectric.com
it
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