may not rank up there with your top 10 engineering
duties: It's costly and time-consuming. Tower work is usually
contracted, so engineers must rely on the honesty and integrity of
the tower inspector. Moreover, we do not often realize immediate
benefits from tower inspections, so they may be viewed as just
Certainly, however, good tower maintenance saves broadcasters from
more costly repairs and lost airtime. Maintenance can even save the
tower itself from early failure. The number of problems discovered
and repaired on tower checkups often reveals the value of regular
How often should a tower be inspected? Inspecting towers every 12 to
24 months is considered wise. It is common for insurance policies to
dictate regular inspections at 12-month intervals.
It is also good engineering practice to get a tower checked after a
significant storm, especially if damage on the ground indicates that
there may be damage overhead. Look for changes in VSWR on
transmitting antennas, an increase in nitrogen or dry-air usage and
post-storm tower lamp failures. Also, listen to the tower for coax
lines slapping in the wind. These conditions warrant a closer look
The tower inspection
Each tower site is unique and presents its own set of challenges
during a thorough inspection. A station can get more for its
inspection dollar by making the job easier for the tower climber.
Make sure the site is accessible, keys are available and work
properly, and other site users are notified for power-reduction
coordination, if necessary. Often overlooked, guy anchors are
critical to the tower's integrity. Clear the area around each guy
anchor prior to inspections.
Look for the following items during a tower inspection.
Tower plumb. A tower typically exhibits one or more physical changes
during its first year. Guy wire stretching and even slight shifts in
the ground will cause slack in the guys and variations in the tower's
plumb. Some tower-erection firms recommend that a new tower be
checked for plumb and guy tension one year after construction and
that subsequent inspections be scheduled if any significant
corrections are needed.
Guy tension. Tower plumb and guy tension are closely related. It is
possible, however, for a tower to be plumb while some or all guys are
too taught or too slack. Tests to determine proper guy tension
include the use of a shunt-type dynamometer, the transit intercept
method, the vibration method and the tension dynamometer method. The
tower manufacturer will often have a preferred method for determining
guy tension. Ask your tower inspector to use that method and show you
Proper paint. Tower paint near the bottom of a tower is easy to see,
but the care that goes into painting the lowest orange and white
bands does not always make it to the top. Have the tower inspector
check for differences in paint quality and alert you to any
Bolts and hardware. Missing or loose hardware is common, especially
at higher points on the tower. Some tower crews have been known to
skimp on hardware and fasteners where they will not be noticed right
away. Coax, conduit and other vertical runs need the same or even
greater attachment frequency up high where the wind is greater. It is
important to check for loose or missing tower bolts, lock washers,
guy attachment hardware, and other critical fasteners and parts.
Guy termination. Guy termination failures, rusted hardware,
improperly installed preforms and ice damage to preforms all carry
responsibility for tower collapses. These problems are relatively
easy to spot and correct during routine inspections.
Turnbuckles should be inspected not only for corrosion but also for
the presence of safety wires. Make sure adjacent turnbuckles are not
rubbing and chafing against each other or other guy wires or hardware.
Guy anchor points are often choked with weeds and vines. Clear these
and other obstacles out of the way. Commercial vegetation killers
will knock down weeds quickly. A longer-lasting choice, if suitable
for use in your area, is a "soil sterilizer." These keep vegetation
under control for up to three years. The guy anchor itself should be
checked for rust, cracks or bends in the steel. It is also helpful to
carefully dig away a few inches of soil to inspect the anchor below
the normal soil level. Corrosion, especially that caused by galvanic
action, can cause severe weakness here.
Transmission line and antenna integrity. Supporting the transmission
lines and antennas is the sole function of most towers. Check all
lines and antennas one foot at a time for leaks, dents, lightning
damage, bullet holes and damage from fallen ice.
Remember to check for the presence of basic hardware and accessories.
Coax runs should have proper hoisting grips installed at recommended
intervals to hold their weight. Proper coax grounding kits are often
overlooked at installation, so check for these and install them if
they are missing. Rigid transmission lines require copious amounts of
hardware along their runs. Make sure you and your tower inspector
know what hanger parts must be present and what condition is
What is legal and what is prudent for tower grounding are usually two
different things. Without specifying a particular grounding scheme, a
typical tower is likely to have just two or three solid copper wires
leading from the tower base to a couple of ground rods. Although this
scheme may satisfy the electrical code, it is not prudent for
broadcasters interested in protecting their tower and transmitter
Before completing a periodic tower inspection, examine those items
relating to safety - both employee and public safety.
Most towers are fenced in some way, thanks to the FCC Rules,
insurance-policy requirements or even local jurisdictional
ordinances. For AM towers, the Rules require "an effective, locked
fence." Keeping fences in good shape is important.
Towers are felled each year by trucks, tractors and backhoes running
into guy anchors or snagging the lowest guy wire. These items need
protection from such vehicles. Fencing, concrete barriers and bright
markings should be used wherever vehicles or heavy equipment could be