For towers that require incandescent lighting, regular tower-light
inspection and maintenance is a task that tower owners must undertake.
Broadcasting's early days saw many station engineers climbing the tower
themselves. The greater availability of qualified tower climbers has
turned this into a regularly occurring event. Regardless, the problem
of changing a burned-out lamp still remains, tower climbers don't come
cheap, and tower lights seldom fail at a convenient time.
I wouldn't go so far as to say that the days of incandescent tower
lighting are numbered, but I think the writing may be on the wall. Two
major companies are offering solid-state lighting equipment for
broadcast towers. At first glance, it seems unreal to consider
solid-state light emitting diodes as replacements for the beacon and
sidelights on a broadcast tower. However, there is power in
to be a direct replacement of the incandescent counterpart.
Dialight and Honeywell, alliance partners for the distribution of
Dialight LED products, now offer side-mount tower lighting fixtures
that are available in steady burning or flashing format. Both companies
offer replacement sidelight and obstruction light units. In addition,
Dialight has produced a beacon assembly that uses high-performance LEDs
in place of the original incandescent lamp bulbs. Both install in place
of the existing incandescent lamp beacon or sidelight, and can use the
wiring that is already in place with no or minor modification.
Off the top and sides
Dialight's LED technology offers a range of lighting products that
operate over a broad voltage range from 12vdc through 220vac. With a
current upper limit of one amp and a total wattage of less than 100
watts, depending on the voltage used, as little as 10% of the
equivalent incandescent power is required.
Among the good features of LEDs is the fact that cold does not
affect them in the way that it can damage incandescent lamps. Extreme
cold and moisture can crack the glass of a regular lamp, stress the
filament, corrode contacts and create difficulty in changing units.
LEDs continue to function regardless of weather conditions and are
expected to outlast incandescent bulbs by many years.
The obstruction light uses 16 LEDs, which provide light output in
accordance with FAA requirements. The epoxy encapsulation of the LED
provides a primary light beam, and a separate assembly cover has a
bulge that forms a Fresnel lens to concentrate the light horizontally.
An interesting human convenience feature is the provision of three
upward shining LEDs, which are viewable from above. This is to confirm
to an observer further up the tower that the light is operating
properly and provides the familiar appearance that we have come to
expect from a properly working sidelight.
Each obstruction light unit is self-contained, except for the
primary power input. When installing one, it is only necessary to
remove the old unit, install the new unit in accordance with the
instructions and connect it to the primary power. The power supply is
contained within the light housing. Either steady- or flashing-light
operation is available depending on FCC license requirements, and this
option does not require any external connections other than power and
the usual flash controller and photo cell.
The initial hardware cost for LED
installation is greater than that for incendescent installation, but
the savings is quickly realized in the reduced power consumption and
The LED system is remarkably resistant to static charges and
lightning strikes. Protection against lightning strikes and power line
surges is afforded by ferrite cores on power interfaces, proper
grounding and shielding, and proprietary protection techniques. The
radiation of internally generated spurious RF signals is prevented by
shielding the encapsulated power supply. This makes this light suitable
for receiving installations where high sensitivity receivers are in
LED tower beacon
The top of the tower is the hardest point for a climber to reach,
and anything that reduces the number of trips up and down the tower is
worth having. LED beacons are designed to be resistant to lightning
strikes and other static surges that could burn out a regular lamp
filament. However, the LED assembly in a beacon is guaranteed to meet
current FCC light output specifications for a period of five years. At
this time, the light output will still be usable but may be at the low
end of the specified limit.
If one of the two LED lamps in the beacon should fail, its demise
will signal the other lamp to shut down also. This action produces an
alarm signal, which will be communicated to the station monitoring
system for proper FAA notification action. In actual operational
conditions, installing an LED beacon is almost a plug-and-play
Protection against electrical surges and voltage spikes exceeding
250 volts, with currents as high as 12,000 amps, is provided by the use
of MOVs and careful grounding.
The power supply is incorporated in the design of the beacon and is
mounted inside the beacon's array of LEDs, directly behind the LED
mounting so that nothing is external to the beacon assembly. The beacon
works with an external, installation-provided control and flasher
Fortunately, faulty beacon service does not involve finding and
replacing the faulty LED among the 640 LEDs used in the beacon. It's
not like a Christmas tree light string, where if one goes, they all go.
It is only necessary to replace the faulty LED assembly with its
built-in power supply to restore full service.
The modules are not intended for end-user servicing. If failure
occurs, the faulty module is returned to the manufacturer for
replacement. The use of encapsulated and fully-shielded power supplies
makes local repair impractical. Another advantage of encapsulation is
better cooling. Air is not the best cooling media, and solid sealing
material carries heat away better than plain air.
Faulty power supplies are discarded by Dialight. They are so epoxy
potted that even the manufacturer can't open and repair them.
The use of LED lighting is growing. Airports are now using LED
taxiing and runway lights. Brake lights on vehicles have adopted them.
Traffic signals are even being upgraded to solid-state. The humble
diode has come a long way from the original crystal detector and a
cat's whisker. We wonder today what will be the next item whose
appearance and operation is changed by electronic excitation.