Radio masts and towers are,
typically, tall structures designed to support antenna (also known as aerials in the
UK) for telecommunications and broadcasting, including television.
They are among the tallest
man-made structures. Similar structures include electricity pylons
and towers for wind turbines
Masts are sometimes named after the broadcasting organisations that
use them, or after a nearby city or town.
Mast was the world's tallest supported structure on
land, but it collapsed in 1991, leaving the KVLY/KTHI-TV
mast as the tallest.
In the case of a mast radiator
radiating tower, the whole mast or tower is itself the transmitting
Mast or tower?
The terms "mast" and "tower" are often used interchangeably.
However, in structural engineering terms, a tower is a
self-supporting or cantilevered
structure, while a mast is held up by stays or guys
Masts tend to be cheaper to build but require an extended area
surrounding them to accommodate the stay blocks. Towers are more
commonly used in cities where land is in short supply.
There are a few borderline designs which are partly free-standing
and partly guyed. For example:
tower consists of a self-supporting tower with a guyed
mast on top.
- The few remaining Blaw-Knox
towers do the opposite: they have a guyed lower section
surmounted by a freestanding part.
- Zendstation Smilde a tall tower with a guyed mast on top (guys go to
- Torre de Collserola a guyed tower, with a guyed mast on top.
(Tower portion is not free-standing.)
Steel lattice tower
The steel lattice is the most widespread form of construction. It
provides great strength, low wind resistance and economy in the use
of materials. Such structures are usually triangular or square in
When built as a stayed mast, usually the whole mast is
parallel-sided. One exception is the Blaw-Knox
When built as a tower, the structure may be parallel-sided or taper
over part or all of its height. When constructed of several sections which
taper exponentially with height, in the manner of the Eiffel Tower, the tower is said to be an Eiffelized one.
Crystal Palace tower in London is an
Some masts are constructed out of steel tubes. In the UK, these were
the subject of collapses at
Moor and Waltham TV stations in the 1960s.
At several cities in Russia and Ukraine, guyed masts were built
between 1960 and 1965 with crossbars running from the mast
structure to the guys. All these masts are tubular structures, used
exclusively for FM/TV transmission. Except for the mast in
Vinnytsia, these masts have heights between 150 and 200
Reinforced concrete towers are relatively expensive to build but
provide a high degree of mechanical rigidity in strong winds. This
can be important when antennas with narrow beamwidths are used,
such as those used for microwave point-to-point links, and when the
structure is to be occupied by people.
In the 1950s, AT&T built numerous concrete towers
, more resembling silos than
towers, for its first transcontinental microwave route.
still in use today.
Germany and the Netherlands most towers constructed for point-to-point
microwave links are built of reinforced concrete, while in the
UK most are
towers can form prestigious landmarks, such as the CN Tower in Toronto.
As well as accommodating technical staff,
these buildings may have public areas such as observation decks or
The Stuttgart TV tower
first tower in the world to be built in reinforced concrete. It was
designed in 1956 by the local civil engineer Fritz Leonhardt
Sapporo TV tower, at Odori park
poles are occasionally used
for low-power non-directional beacons or medium-wave broadcast
There are fewer wooden towers now than in the past. Many were built
in the UK during World War II
of a shortage of steel. In Germany before World War II wooden towers
were used at nearly all medium-wave transmission sites, but all of
these towers have since been demolished, except for the Gliwice
Relay is an example of a TV relay transmitter using a
Other types of antenna supports and structures
Shorter masts may consist of a self-supporting or guyed wooden
pole, similar to a telegraph pole. Sometimes self-supporting
tubular galvanized steel
used: these may be termed monopoles
In some cases, it is possible to install transmitting antennas on
the roofs of tall buildings. In North
America, for instance, there are transmitting antennas on the
Building, the Sears
Tower, and formerly on the World Trade Center towers.
When the buildings collapsed,
several local TV and radio stations were knocked off the air until
backup transmitters could be put into service. Such facilities also
exist in Europe
, particularly for portable
radio services and low-power FM
Many people view bare cellphone
ugly and an intrusion into their neighbourhoods. Even though people
increasingly depend upon cellular communications, they are opposed
to the bare towers spoiling otherwise scenic views. Many companies
offer to 'hide' cellphone towers as trees, church towers, flag
poles, water tanks and other features. There are many providers
that offer these services as part of the normal tower installation
and maintenance service. These are generally called "stealth
towers" or "stealth installations".
The level of detail and realism achieved by disguised cellphone
towers is remarkably high; for example, such towers disguised as
trees are nearly indistinguishable from the real thing, even for
local wildlife (who additionally benefit from the artificial
flora). Such towers can be placed unobtrusively in
national parks and other such
protected places, such as towers disguised as cacti in Coronado National Forest.
Even when disguised, however, such towers can create controversy; a
tower doubling as a flagpole attracted controversy in 2004 in
relation to the U.S. Presidential campaign of that
, and highlighted the sentiment that such disguises serve
more to allow the installation of such towers in subterfuge away
from public scrutiny rather than to serve towards the
beautification of the landscape.
A mast radiator is a radio tower or mast in which the whole
structure works as an antenna. It is used frequently as a
transmitting antenna for long
or medium wave
Structurally, the only difference is that a mast radiator may be
supported on an insulator at its base. In the case of a tower,
there will be one insulator supporting each leg.
Telescopic, pump-up and tiltover towers
A special form of the radio tower is the telescopic mast
These can be erected very quickly. Telescopic masts are used
predominantly in setting up temporary radio links for reporting on
major news events, and for temporary communications in emergencies.
They are also used in tactical military networks. They can save
money by needing to withstand high winds only when raised, and as
such are widely used in amateur
Telescopic masts consist of two or more concentric sections and
come in two principal types:
- Pump-up masts are often used on vehicles and are raised to
their full height pneumatically or hydraulically. They are usually
only strong enough to support fairly small antennas.
- Telescopic lattice masts are raised by means of a winch, which
may be powered by hand or an electric motor. These tend to cater
for greater heights and loads than the pump-up type. When
retracted, the whole assembly can sometimes be lowered to a
horizontal position by means of a second tiltover winch. This
enables antennas to be fitted and adjusted at ground level before
winching the mast up.
Balloons and kites
A tethered balloon
or a kite
can serve as a temporary support. It can
carry an antenna or a wire (for VLF, LW or MW) up to an appropriate
height. Such an arrangement is used occasionally by military
agencies or radio amateurs. The American broadcasters TV Martí broadcast a television program to
Cuba by means of such a balloon.
balloon was also used for the British GQV
experimental transmitter in 2003.
Other special structures
For two VLF
antennas spun across deep valleys are used. The wires are supported
by small masts or towers or rock anchors. See List of spans:
Antenna spans across valleys
. The same technique was also used
for the Criggion VLF
For ELF transmitters ground dipole
antennas are used. Such structures require no tall masts. They
consist of two electrodes buried deep in the ground at least a few
dozen kilometres apart. From the transmitter building to the
electrodes, overhead feeder lines run. These lines look like power
lines of the 10 kV level, and are installed on similar
Economic and aesthetic considerations
A radio amateur's do-it-yourself
- The cost of a mast or tower is roughly proportional to the
square of its height.
- A guyed mast is cheaper to build than a self-supporting tower
of equal height.
- A guyed mast needs additional land to accommodate the guys, and
is thus best suited to rural locations where land is relatively
cheap. An unguyed tower will fit into a much smaller plot.
- A steel lattice tower is cheaper to build than a concrete tower
of equal height.
- Two small towers may be less intrusive, visually, than one big
one, especially if they look identical.
- Towers look less ugly if they and the antennas mounted on them
- Concrete towers can be built with aesthetic design - and they
are, especially in Continental Europe. They are sometimes built in
prominent places and include observation decks or restaurants.
Masts for HF/shortwave antennas
For transmissions in the shortwave
there is little to be gained by raising the antenna more than a few
above ground level. Shortwave
transmitters rarely use masts taller than about 100 metres.
Access for riggers
Because masts, towers and the antennas mounted on them require
maintenance, access to the whole of the structure is necessary.
Small structures are typically accessed with a ladder
. Larger structures, which tend to require more
frequent maintenance, may have stairs and sometimes a lift.
Aircraft warning features
Tall structures in excess of certain legislated heights are often
equipped with aircraft warning
, usually red, to warn pilots of the structure's
existence. In the past, ruggedized and under-run filament lamps
were used to maximize the bulb life. Nowadays such lamps tend to
Height requirements vary across states and countries, and may
include additional rules such as requiring a white flashing strobe
in the daytime and pulsating red fixtures at night. Structures over
a certain height may also be required to be painted with
contrasting color schemes such as white and orange or white and red
to make them more visible against the sky.
Light pollution and nusiance lighting
In some countries where light
is a concern, tower heights may be restricted so as
to reduce or eliminate the need for aircraft warning lights. For
example in the United States the 1996 Telecommunications Act
allows local jurisdictions to set maximum heights for towers, such
as limiting tower height to below 200 feet and therefore not
requiring aircraft illumination under FCC
The limit is more commonly set to 190 or 180 feet to allow for
masts extending above the tower.
One problem with radio masts is the danger of wind-induced
oscillations. This is particularly a concern with steel tube
construction. One can reduce this by building cylindrical
shock-mounts into the construction. One finds such shock-mounts, which look
like cylinders thicker than the mast, for example, at the radio
masts of DHO38 in Saterland.
There are also constructions, which consist
of a free-standing tower (usually from reinforced concrete
), onto which a guyed
radio mast is installed. The best known such construction is the
Tower in Lopik (the
Netherlands). Further towers of this building method can
be found near Smilde (the Netherlands) and Waldenburg (Baden-Württemberg, Germany).
- Some New York City TV and Radio Stations Off
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- Cell Phone Trees
- Sreevidya, S., and Subramanian, N., Aesthetic Appraisal to
Antenna Towers, Journal of Architectural Engineering, American
Society of Civil Engineers, Vol. 9, No. 3, September 2003, pp.