Aerospace and Electronic Systems Magazine March 2017 - 16

Historical Article:

DOI. No. 10.1109/MAES.2017.160076

Coltano: The Forgotten Story of Marconi's Early
Powerful Intercontinental Station
Filippo Giannetti, University of Pisa, Italy

INTRODUCTION

CONCEIVING A NEW POWERFUL INTERCONTINENTAL
RADIOTELEGRAPHIC STATION

"There, do you see Admiral?" Marconi stated. "On
that far plain, behind Leghorn, a large Italian radio
station could be built, even larger than the British
station in Poldhu." [1].
On September 8, 1902, at the dawn of the wireless telegraphy
age, Marconi was looking at the Tuscan coast from the cruiser
"Carlo Alberto," back from a long trip where he successfully
carried out many radio experiments in the northern seas. While
passing in front of Leghorn, Marconi expressed to the Admiral
Mirabello his intention to build a powerful intercontinental station in the plain behind that city. The station, which would be the
first in Marconi's home country (and one of the first in the world,
too), was intended to provide radiotelegraphic connections with
Africa and America in the very low-frequency (VLF) band, i.e.,
using carrier frequencies below 100 kHz, which, at the time, were
believed to be the sole option for long-distance radio communications.1
The selected site for this purpose was Coltano, a marshy
rural area between Pisa and Leghorn, near the Tyrrhenian Sea
(Figure 1). The station was inaugurated by Marconi himself
in 1911 with transmissions to Clifden (Ireland) and Glace Bay
(Canada) (Figure 2), followed by a pioneeristic link reaching
Massawa (Eritrea), across more than 2000 km of Sahara's dry
soil; which, until then, was considered an insurmountable obstacle for the propagation of low-frequency ground waves. This
was just the first of a series of successes obtained by this once
worldwide renowned, but now completely forgotten, radio station, born from Marconi's genius.

Though the standard definition of VLF band refers to the range
3-30 kHz, for simplicity in the following we denote as VLF the
whole frequency interval below 100 kHz.

Author's current address: University of Pisa, Department of
Information Engineering, Via G. Caruso 16, Pisa, I-56122 Italy.
E-mail: (filippo.giannetti@iet.unipi.it).
Manuscript received March 23, 2016, revised July 13, 2016, and
ready for publication July 23, 2016.
Review handled by M Greco.
0885/8985/17/$26.00 © 2017 IEEE
16

In September 1902, after the successful validation of his wireless transmissions across the Atlantic and a subsequent extensive test campaign carried out in the North Sea and the Baltic
Sea on board the "Carlo Alberto" cruiser of the Italian Royal
Navy (IRN), Guglielmo Marconi expressed his intent to build a
powerful intercontinental radiotelegraphic station in Italy. Such
a decision did not stem from a sudden intuition of the great scientist, but rather was the first step of a strategy that was devised
by Marconi's Wireless Telegraph Company for a commercial
expansion in Italy. This is clearly testified by a document conserved in the Marconi's Archives of the Bodleian Library, at the
University of Oxford, dated August 25th, 1902, wherein Guglielmo Marconi is appointed as the company's representative in
"the negotiations with the Government of the Kingdom of Italy
[...] for the erection, establishment and maintenance [...] of a
high power Marconi station for the purpose of reception and
transmission of messages by means of the Marconi system of
wireless telegraphy." [2].
The original intent of Marconi, as illustrated to King Vittorio Emanuele III, was to build a radio station capable of connecting Italy with South America (see [3, pp. 109-110]), which
hosted a large number of Italian emigrants. However, this goal
was soon abandoned, probably because of the technical difficulty of a wireless transmission over such a huge distance. The
station was then proposed with the aim of providing radio links
with North America and the Italian colonies in East Africa. Being conceived for intercontinental services, this new radio station belonged to the category of so-called "ultra-powerful stations." In 1903 there were only three operational ultra-powerful
stations: one in Britain, one in the U.S. and one in Canada ([3,
p. 101]).
Coltano, a swampy rural area about 10 km south of Pisa,
in Tuscany (Figure 1), was the selected site due to a number
of favorable factors, listed in Box 1. One outstanding feature
orienting Marconi's choice was the high electrical conductivity of Coltano's damp soil which allows ground waves to glide
along the surface of the Earth, especially at lower frequencies,
thus easing the propagation of radio signals (see [4, ch. V, sec.
11], and [5]). The map in Figure 3 illustrates the electrical
conductivity of the soil in Tuscany, obtained from a nation-

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MARCH 2017

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