Aerospace and Electronic Systems Magazine March 2017 - 19

Giannetti

Figure 5.

(a)Values of the range factor ρ (in bold red) for ground waves radiated
from Coltano at different frequencies (from [10]). (b) Range factor ρ vs.
frequency for ground waves radiated from Coltano.

The construction started in 1905 under the supervision of
Marquis Luigi Solari, Marconi's most trusted assistant. The work,
however, proceeded at a slow pace due to workers' strikes [8], but
mainly due to the harsh and wet environment that caused the station's wooden roof to rot and metal structures to rust, so impairing
the stability of the high antenna towers. The photo in Figure 6a
shows Marconi (fifth from left) in front of the station building,
almost completed, during a visit on June 6, 1910. The building was
completed in October 1910 (Figure 6b) and was named "Palazzina
Marconi" (Marconi's House). The whole station, depicted in the
bottom-left part of the plan in Figure 7 (from [9]), was ready in
November 1911.3
The Palazzina Marconi (labelled "1" in Figure 7) hosted an
asynchronous rotary spark gap transmitter, like that available in the
Clifden station (Ireland) [11], [12]. Coltano's transmitter operated
at 43 kHz (7000 m wavelength) [11], [13], and fed two VLF bent
antennas (labelled "7" and "8" in Figure 7), whose design concept
is described in Box 3. The power consumption of the station was
about 300 kW [14] and the transmit power is estimated to be 14
kW [15].
3

It is worthwhile to notice that the Palazzina Marconi in Figure 6a
(dated 1910) has a roof terrace with a balustrade, while in Figure
6b (dated 1911 or later) it exhibits a hip roof. This modification
was adopted on-the-fly during the final phases of the construction in order to provide better protection against humidity.

MARCH 2017

Figure 6.

(a) Marconi (fifth from left) in front of the Coltano station building on
June 6, 1910. (b) The Palazzina Marconi (old radio) and the 8 pylons of
the VLF continental aerial.

Each VLF antenna extended for 530 m and had 4 pairs of towers with transversal riggings that suspended 24 horizontal parallel
wires. Each of the 8 towers was made of a 45-m high trellis (somehow resembling the Eiffel Tower), surmounted by a 30-m high
wooden mast, so that the antenna wires hang at 75 m above the
ground. A special team of skilled sailors of the IRN was engaged
for working at such a considerable height during the installation
and maintenance operations. In the illustration in Figure 6b the
Palazzina Marconi and the 8 Eiffel Tower-like pylons of the socalled continental aerial are depicted. Each VLF bent antenna had
a natural wavelength of about 3000 m, a static capacitance of 17
nF, and, for a wavelength of 5800 m (corresponding to 51.7 kHz),
the impedance was about 5 Ω [9].
In November 1910, some tests were carried out [20]. First,
on Nov. 13, 1910, at 12:00 p.m., a test signal (not a telegram)
was transmitted from Coltano station, which was not yet completed at this time, and was clearly received by the Marconi
station in Glace Bay (Canada), 5360 km away, and by the newly-built Italian colonial station in Massawa (Eritrea), 4160 km
away. The result was impressive since the experiment was per-

IEEE A&E SYSTEMS MAGAZINE

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