It was in the end of 1980s, during at my
trip by bus from Gorkiy (now Nizniy
Novgorod, Russia) to a small town at this region, while on route
to my destination, I observed a huge field fenced with barbed
wire. I asked my local fellow traveler what it might be and he
replied that it was a military communications site. However, I
noticed there weren't any antennas visible. My companion remarked
that they were installed under ground!
So, for the first time I had seen an underground communications
The manner of constructing the underground
antennas used on these sites especially interested me, but at
the times I cannot found any information about underground antennas.
Information of these antennas was considered highly confidential
just before 90s. Recently with development of satellite and meteor
radio communications systems such unusual antennas became almost
obsolete. Classifications have been removed from underground
and spreading antennas and information on the antennas may be
found in the internet.
However, underground and spreading antennas are old type of
antennas used by military of different countries. These antennas
usually were exploited on classified signal radio communications
and spreading antennas are normally not used by the radio amateurs.
Usually there are enough places where it is possible to install
an antenna of choice. However, with cities getting larger and
architectural demands to keep the exterior of houses and communities
and spreading antennas may be one of the only solutions to be
on the Air.
of Underground and Spreading Antennas
During the First World War, an antenna mast of a field radio set had
a significant altitude of 15-30 meters (50-100 feet) thereof it
represented an easy target for enemy's artillery. But even when
shells were downed the mast the spreading above the ground antenna
allowed makes radio communication. It was found that the spreading
antenna enabled fair communication in the same direction of the
antenna wire leading from the transmitter. Knowing thus fact sometimes
mast was not be installed for field radio set and military use
the spreading antenna that represented just wire in thick insulation
lying on the top of the ground which follows and blends with the
irregularities of the earth surface and vegetation coverage.
Before the Second World War early researches into the operation of underground
and spreading antennas were made for the purpose of espionage
installation of invisible antennas. These antennas needed be easily
installed and set up for operation on short-wave bands of 2-5
or 8-12 MHz, which was commonly used at the times by the spies
for clandestine operation.
In practical way it was found that an effective spreading antenna may
be formed from a wire of about 1 mm diameter enclosed by a dielectric
with approximately 10-mm diameter to protect the wire from touching
the ground surface. However as usual for clandestine spreading
antenna it was used general electric wire in rubber isolation
in length of about 30-45 meters. The wire may be placed on the
ground, on the bushes or attached to a fence. It was easy installed
and easy removed for radio operation and the wire may be easily
found in a local electrical store.
Old direction-finding equipment had some irregular errors in finding
location of transmitters using spreading and underground antennas.