and his wireless stations in Wales
A Book Review
By David J. Jefferies
our reviewer found this little book on a visit to the Snowdonia National Park, North Wales, UK, in a shop attached to the old slate mine museum in Llanberis, a village at the foot of Mount Snowdon (Yr Wyddfa). A speculative expenditure of four pounds and fifty pence resulted in a wealth of fascinating technical detail about the first transatlantic wireless transmissions, which were on long wave.
The book is divided into three topics: the history of early commercial wireless communications; biographies of Marconi and the other associated protagonists; and technical information about early very high power spark wireless telegraphy transmitters, receivers, and antennas.
There is a preface, six chapters, a bibliography, acknowledgments, and an index. The chapters are entitled:
1. William Henry Preece, 1834-1913
2. The Progress of Science
3. Guglielmo Marconi, 1874-1937
4. Bridging the Atlantic Ocean
5. The Stations in Wales
6. Technical Notes
In chapter 6 there are subsections on:
1. The Hertz Transmitter
2. Marconi's Early Apparatus
4. The Magnetic Detector
5. The Poldhu Transmitter
6. The Disc Discharger
7. The Poulsen Arc Generator
8. The Alexanderson Alternator
9. The Valve Transmitter
William Preece was a native of Caernarfon, a coastal town in North Wales fortified by King Edward the First when the English tried to subdue the Welsh. See the picture taken this July. Preece rose to be Engineer-in-Chief of the British Post Office, in charge of the technical side of all telegraph services in Britain. He was a vigorous supporter of Bell's telephone and later, Marconi's Wireless Telegraphy against what appears to have been some hide-bound opposition by the vested interests. It was his interventions that got Marconi his foothold in Britain and enabled him to develop wireless communications for commercial purposes. The existing academic community rather resented the representation of Marconi's commercial development with the term "Marconi - inventor of wireless" and existing telegraph companies were first skeptical, and then later fearful of the new technologies.
Preece himself had used the near field of telegraph cable to communicate over several km, by inductive loop transmission. Having been visited by Marconi in London in 1896, he rapidly realised that communication by the radiation field rather than the inductive near field held far more possibilities. Preece retired at the age of 65 in 1899, but kept up his support for the emerging technology of wireless telegraphy. He set up a consultancy business, and introduced electric light to Caernarfon.
By 1894, all the necessary knowledge was in place to make a functional wireless telegraphy system, but it fell to Marconi to commercialise the technology which had been developed in various university laboratories. Marconi was only 20 in 1894, which was the year that Hertz died, and Marconi had developed a strong interest in Hertzian waves despite repeatedly failing his academic exams.
Incidentally, this lends support to the views of the film-maker Stanley Kubrick, who was of the opinion that education is largely wasted unless it encourages interest, and that sufficient interest can compensate for lack of formal education.
Marconi had a neighbour, Professor Augusto Righi, who had been experimenting on Hertzian waves and who encouraged him. He set up two rooms in his family's house as laboratories (he had a well-off father) and soon he found that he could transmit into the garden. He also discovered that the range was increased when he raised one of the Hertzian plates in the air, and placed the other on the ground. Thus, it would be true to say that "Marconi invented (or discovered) antennas". And also, by the methods still used today by many amateur experimenters, rather than being guided by theory.
Marconi also had the idea of keying the transmitter so that it could send Morse code signals.
After further development of his antennas, his father found that supporting his son's activities was costing rather too much money so Marconi approached the Italian Ministry of posts and Telegraphs in Rome. They rebuffed him, reminding him to safeguard the interests of Italy should he patent his system. He was advised to go to London as there was more possibility of funding from the British, who were a maritime nation and very interested in communications with ships. ("mobile" rather than "fixed" communications - still wireless over 100 years later).
Marconi's mother, Annie Jameson, from the Irish whiskey family, had a nephew, who was an engineer, in London (Henry Jameson-Davis) to whom Marconi went in 1896 at the age of 22. His delicate radio apparatus suffered damage in an over-zealous customs inspection, so he had to repair it and immediately applied for a patent (2 June 1896, complete specs filed 2 March 1897). Henry's engineering contacts led Marconi to demonstrate his apparatus to Preece. The early demonstrations were widely reported in the press.
Marconi applied Oliver Lodge's tuned circuit selectivity ideas to his wireless communications to allow multiple links to work simultaneously at close distances to each other. This was patented in April 1900, and gave Marconi's company a competitive edge. At the same time Marconi's experiments showed that the radio waves could travel beyond the horizon, against all the accepted academic wisdom of the time.
Marconi then set his sights on providing wireless communications across the Atlantic, in competition with the undersea cables. He set up transmitting and receiving stations at Poldhu in Cornwall and at Wellfleet, Cape Cod, Massachusetts. The antennas at both ends were damaged by storms. Marconi moved his American station to St John's, Newfoundland, to lessen the range, and on 12 December 1901 he heard the letter "S" in Morse code transmitted from Cornwall. The antenna was 150 metres of wire carried on a kite.
After legal intervention from the telegraph company Anglo-American Telegraph claiming telegraphic monopoly on Newfoundland, Marconi was offered facilities by the Canadian and Nova Scotia governments and set up his transatlantic station at Glace Bay, on Cape Breton Island. The transmitter here was powered by a 75 kilowatt alternator, driven by a steam engine. The wavelength of the first transmissions could not be measured, but was estimated to be 366 metres. Later, the link was changed to 1100 metres. Marconi demonstrated that communication range increased at night, by sailing across the Atlantic on a ship equipped with a receiver.
As the technology improved, range increased and the UK end of the link was moved to a
site at the village of Waunfawr, a few miles South of Caernarfon and on the side of
a Welsh hill at a height of 207 metres above mean sea level. The terrain may be seen in
the panorama from the top of Snowdon, a few miles away...
http://www.eryptick.net/wales/snowdon.htm By this time, the receiving end of the links were separated from the transmitting end of the links by some tens of km, and the transmitters were keyed from the receiving station.
These transmitters were very high power spark gap transmitters and the selectivity was provided by robust tuned circuits coupled to large long wave antenna structures. Marconi found that the inverted L antenna was an improvement, and also directional in the direction of the horizontal wire. A circuit diagram of one of these heavy duty spark transmitters is shown here.
The antenna installation at Waunfawr is shown here.
Chapter 6 of this book contains fascinating technical detail about the engineering of the high power transmitters and the detectors used in these early days.
This little book is well-written, and written from a professional engineering point of view, and it has relevance today to the onward march of technology in its historical story. Your reviewer enjoyed it hugely and recommends it highly. Do not try to copy the spark transmitter design principles in these pages; this will be illegal, antisocial, and potentially dangerous. However, it is very interesting to see how simple technology (in everything except scale) can be used to bridge the Atlantic.
Title: Marconi and his wireless stations in Wales
Author: Hari Williams CEng MIEE
Publisher: Carreg Gwalch
Details: Paperback, 110 pages including 15 pages of photos, and 14 figures
Size 12.3cm by 18.3cm by 0.8cm, Weight 0.13kg
Price: UK pounds 4.50
School of Electronics, Computing, and Mathematics
University of Surrey
Guildford GU2 7XH